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prostate cancer

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Medical Encyclopedia: Prostate Cancer

Definition

Prostate cancer is a disease in which cells of the prostate become abnormal and start to grow uncontrollably, forming tumors.

Description

Prostate cancer is a malignancy of one of the major male sex glands. Along with the testicles and the seminal vesicles, the prostate secretes the fluid that makes up semen. The prostate is about the size of a walnut and lies just behind the urinary bladder. A tumor in the prostate interferes with proper control of the bladder and normal sexual functioning. Often the first symptom of prostate cancer is difficulty in urinating. However, because a very common, non-cancerous condition of the prostate, benign prostatic hyperplasia (BPH), also causes the same problem, difficulty in urination is not necessarily due to cancer.

Cancerous cells within the prostate itself are generally not deadly on their own. However, as the tumor grows, some of the cells break off and spread to other parts of the body through the lymph or the blood, a process known as metastasis. The most common sites for prostate cancer to metastasize are the seminal vesicles, the lymph nodes, the lungs, and various bones around the hips and the pelvic region. The effects of these new tumors are what can cause death.

Second only to skin cancer, the American Cancer Society estimates that in 2000 at least 180,400 new cases of prostate cancer were diagnosed. Of this number, the disease will cause at least 31,900 deaths. Although prostate cancer is often very slow growing, it can be aggressive, especially in younger men. Given its slow growing nature, many men with the disease die of other causes rather than from the cancer itself.

Prostate cancer affects African-American men twice as often as white men and the mortality rate among African-Americans is also two times higher. African-Americans have the highest rate of prostate cancer of any world population group.

— Lata Cherath; Michelle Johnson, MS, JD



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Britannica Concise Encyclopedia: prostate cancer
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Malignant tumour of the prostate gland. Prostate cancer commonly occurs in men over age 50. Symptoms include frequent or painful urination, blood in the urine, sexual dysfunction, swollen lymph nodes in the groin, and pain in the pelvis, hips, back, or ribs. The likelihood of developing prostate cancer doubles if there is a family history. Treatment may include surgery, radiation therapy, hormone therapy, chemotherapy, or a combination of two or more of these approaches.

For more information on prostate cancer, visit Britannica.com.

Oncology Encyclopedia: Prostate Cancer
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Key Terms: Antiandrogen, Benign Prostate Hyperplasia, Brachytherapy, Gleason Grading System, Granulocyte/macrophage colony stimulating factor, Histopathology, Luteinizing hormone releasing hormone (LHRH) agonist, Orchiectomy, Prostate-Specific Antigen, Radical Prostatectomy.

Definition

Prostate cancer is a disease in which cells in the prostate gland become abnormal and start to grow uncontrollably, forming tumors.

Description

Prostate cancer is a malignancy of one of the major male sex glands. Along with the testicles and the seminal vesicles, the prostate secretes the fluid that makes up semen. The prostate is about the size of a walnut and lies just behind the urinary bladder. A tumor in the prostate interferes with proper control of the bladder and normal sexual functioning. Often the first symptom of prostate cancer is difficulty in urinating. However, because a very common, non-cancerous condition of the prostate, benign prostatic hyperplasia (BPH), also causes the same problem, difficulty in urination is not necessarily due to cancer.

Cancerous cells within the prostate itself are generally not deadly on their own. However, as the tumor grows, some of the cells break off and spread to other parts of the body through the lymph or the blood, a process known as metastasis. The most common sites for prostate cancer to metastasize are the seminal vesicles, the lymph nodes, the lungs, and various bones around the hips and the pelvic region. The effects of these new tumors are what can cause death.

Demographics

Prostate cancer is the most commonly diagnosed malignancy among adult males in Western countries. Although prostate cancer is often very slow growing, it can be aggressive, especially in younger men. Given its slow growing nature, many men with the disease die of other causes rather than from the cancer itself.

Prostate cancer affects African-American men twice as often as white men; the mortality rate among African-Americans is also two times higher. African-Americans have the highest rate of prostate cancer of any world population group.

Causes and Symptoms

The precise cause of prostate cancer is not known. However, there are several known risk factors for disease including age over 55, African-American heritage, a family history of the disease, occupational exposure to cadmium or rubber, and a high-fat diet. Men with high plasma testosterone levels may also have an increased risk for developing prostate cancer.

Frequently, prostate cancer has no symptoms and the disease is diagnosed when the patient goes for a routine screening examination. However, when the tumor is big or the cancer has spread to the nearby tissues, the following symptoms may be seen:

  • weak or interrupted flow of the urine
  • frequent urination (especially at night)
  • difficulty starting urination
  • inability to urinate
  • pain or burning sensation when urinating
  • blood in the urine
  • persistent pain in lower back, hips, or thighs (bone pain)
  • painful ejaculation

Diagnosis

Prostate cancer is curable when detected early. Yet the early stages of prostate cancer are often asymptomatic, so the disease often goes undetected until the patient has a routine physical examination. Diagnosis of prostate cancer can be made using some or all of the following tests.

Digital Rectal Examination (DRE)

In order to perform this test, the doctor puts a gloved and lubricated finger (digit) into the rectum to feel for any lumps in the prostate. The rectum lies just behind the prostate gland, and a majority of prostate tumors begin in the posterior region of the prostate. If the doctor does detect an abnormality, he or she may order more tests in order to confirm these findings.

Blood Tests

Blood tests are used to measure the amounts of certain protein markers, such as prostate-specific antigen (PSA), found circulating in the blood. The cells lining the prostate generally make this protein and a small amount can be detected normally in the bloodstream. In contrast, prostate cancers produce a lot of this protein, significantly raising the circulating levels. A finding of a PSA level higher than normal for the patient's age group therefore suggests that cancer is present.

Transrectal Ultrasound

A small probe is placed in the rectum and sound waves are released from the probe. These sound waves bounce off the prostate tissue and an image is created. Since normal prostate tissue and prostate tumors reflect the sound waves differently, the test is an efficient and accurate way to detect tumors. Though the insertion of the probe into the rectum may be slightly uncomfortable, the procedure is generally painless and only takes 20 minutes.

Prostate Biopsy

If cancer is suspected from the results of any of the above tests, the doctor will remove a small piece of prostate tissue with a hollow needle. This sample is then checked under the microscope for the presence of cancerous cells. Prostate biopsy is the most definitive diagnostic tool for prostate cancer, and this procedure is done quickly and with little pain or discomfort.

Prostate cancer can also be diagnosed based on the examination of the tissue removed during a transurethral resection of the prostate (TURP). This procedure is performed to help alleviate the symptoms of BPH, a benign enlargement of the prostate. Like a biopsy, this is a definitive diagnostic method for prostate cancer.

X Rays and Imaging Techniques

A chest x ray may be ordered to determine whether the cancer has spread to the lungs. Imaging techniques (such as computed tomography (CT) scans and magnetic resonance imaging (MRI)), where a computer is used to generate a detailed picture of the prostate and areas nearby, may be done to get a clearer view of the internal organs. A bone scan may be used to check whether the cancer has spread to the bone.

Treatment Team

Prostate cancer is often treated by a team of specialists including a urologist (who may or may not perform surgery), a surgeon (if surgical treatment is used and it is not performed by the urologist), a medical oncologist, and, if radiation therapy is used, a radiation oncologist.

Clinical Staging, Treatments, and Prognosis

Once cancer is detected during the microscopic examination of the prostate tissue during a biopsy or TURP, doctors will determine two different numerical scores that will help define the patient's treatment and prognosis.

Tumor Grading

Initially, the pathologist will grade the tumor based on his or her examination of the biopsy tissue. The pathologist scores the appearance of the biopsy sample using the Gleason system. This system uses a scale of one to five based on the sample's similarity or dissimilarity to normal prostate tissue. If the tissue is very similar to normal tissue, it is still well differentiated and given a low grading number, such as one or two. As the tissue becomes more and more abnormal (less and less differentiated), the grading number increases, up to five. Less differentiated tissue is considered more aggressive and more likely to be the source of metastases.

The Gleason grading system is best predictive of the prognosis of a patient if the pathologist gives two scores to a particular sample—a primary and a secondary pattern. The two numbers are then added together and that is the Gleason score reported to the patient. Thus, the lowest Gleason score available is two (a primary and secondary pattern score of one each). A typical Gleason score is five (which can be a primary score of two and a secondary score of three or visa-versa). The highest score available is 10, with a pure pattern of very undifferentiated tissue, that is, of grade five. The higher the score, the more abnormal behavior of the tissue, the greater the chance for metastases, and the more serious the prognosis after surgical treatment. A study found that the ten-year cancer survival rate without evidence of disease for grade two, three, and four cancers is 94% of patients. The rate is 91% for grade five cancers, 78% for grade six, 46% for grade seven, and 23% for grade eight, nine, and ten cancers.

Cancer Staging

The second numeric score determined by the doctor will be the stage of the cancer, which takes into account the grade of the tumor determined by the pathologist. Based on the recommendations of the American Joint Committee on Cancer (AJCC), two kinds of data are used for staging prostate cancer. Clinical data is based on the external symptoms of the cancer, while histopathological data is based on surgical removal of the prostate and examination of its tissues. Clinical data is most useful to make treatment decisions, while pathological data is the best predictor of prognosis. For this reason, the staging of prostate cancer takes into account both clinical and histopathologic information. Specifically, doctors look at tumor size (T), lymph node involvement (N), the presence of visceral (internal organ) involvement (metastasis = M), and the grade of the tumor (G).

The classification of tumor as T1 means the cancer that is confined to the prostate gland and the tumor that is too small to be felt during a DRE. T1 tumors are often found after examination of tissue removed during a TURP. The T1 definition is subdivided into those cancers that show less than 5% cancerous cells in the tissue sample (T1a) or more than 5% cancerous cells in the tissue sample (T1b). T1c means that the biopsy was performed based on an elevated PSA result. The second tumor classification is T2, where the tumor is large enough to be felt during the DRE. T2a indicates that only the left or the right side of the gland is involved, while T2b means both sides of the prostate gland has tumor.

With a T3 tumor, the cancer has spread to the connective tissue near the prostate (T3a) or to the seminal vesicles as well (T3b). T4 indicates that cancer has spread within the pelvis to tissue next to the prostate such as the bladder's sphincter, the rectum, or the wall of the pelvis. Prostate cancer tends to spread next into the regional lymph nodes of the pelvis, indicated as N1. Prostate cancer is said to be at the M1 stage when it has metastasized outside the pelvis in distant lymph nodes (M1a), bone (M1b) or organs such as the liver or the brain (M1c). Pain, weight loss, and fatigue often accompany the M1 stage.

The grade of the tumor (G) can be assessed during a biopsy, TURP surgery, or after removal of the prostate. There are three grades recognized: G1, G2, and G3, indicating the tumor is well, moderately, or poorly differentiated, respectively. The G, LN, M descriptions are combined with the T definition to determine the stage of the prostate cancer.

  • Stage I prostate cancer comprises patients who are T1a, N0, M0, G1.
  • Stage II includes a variety of condition combinations including T1a, N0, M0, G2, 3 or 4; T1b, N0, M0, Any G; T1c, N0, M0, Any G; T1, N0, M0, Any G or T2, N0, M0, Any G.
  • Stage III prostate cancer occurs when conditions are T3, N0, M0, any G.
  • Stage IV is T4, N0, M0, any G; any T, N1, M0, any G; or any T, any N, M1, Any G.

Prognosis

The prognosis for cancers at Stages I and II is very good. For men treated with stage I or stage II disease, over 95% are alive after five years. Although the cancers of Stage III are more advanced, the five-year prognosis is still good, with 70% of men diagnosed at this stage still living. The spread of the cancer into the pelvis (T4), lymph (N1), or distant locations (M1) are very significant events, as the five-year survival rate drops to 30% for Stage IV.

Treatment Options

The doctor and the patient will decide on the treatment mode after considering many factors. For example, the patient's age, the stage of the disease, his general health, and the presence of any co-existing illnesses have to be considered. In addition, the patient's personal preferences and the risks and benefits of each treatment protocol are also taken into account before any decision is made.

Surgery

For stage I and stage II prostate cancer, surgery is the most common method of treatment because it theoretically offers the chance of completely removing the cancer from the body. Radical prostatectomy involves complete removal of the prostate. The surgery can be done using a perineal approach, where the incision is made between the scrotum and the anus, or using a retropubic approach, where the incision is made in the lower abdomen. Perineal approach is also known as nerve-sparing prostatectomy, as it is thought to reduce the effect on the nerves and thus reduce the side effects of impotence and incontinence. However, the retropubic approach allows for the simultaneous removal of the pelvic lymph nodes, which can give important pathological information about the tumor spread.

The drawback to surgical treatment for early prostate cancer is the significant risk of side effects that impact the quality of life of the patient. Even using nerve-sparing techniques, studies by the National Cancer Institute (NCI) found that 60% to 80% of men treated with radical prostatectomy reported themselves as impotent (unable to achieve an erection sufficient for sexual intercourse) two years after surgery. This side effect can be sometimes countered by prescribing sildenafil citrate (Viagra). Furthermore, 8% to 10% of patients were incontinent in that time span. Despite the side effects, the majority of men were reported as satisfied with their treatment choice. Additionally, there is some evidence that the skill and the experience of the surgeon are central factors in the ultimate side effects seen.

A second method of surgical treatment of prostate cancer is cryosurgery, or cryotherapy. Guided by ultrasound, surgeons insert up to eight cryoprobes through the skin and into close proximity with the tumor. Liquid nitrogen (temperature of -320.8 degrees F, or -196 C) is circulated through the probe, freezing the tumor tissue. In prostate surgery, a warming tube is also used to keep the urethra from freezing. Patients currently spend a day or two in the hospital following the surgery, but it could be an outpatient procedure in the near future. Recovery time is about one week. Side effects have been reduced in recent years, although impotence still affects almost all who have had cryosurgery for prostate cancer. Cryo-surgery is considered a good alternative for those too old or sick to have traditional surgery or radiation treatments or when these more traditional treatments are unsuccessful. There is limited amount of information about the long-term efficacy of this treatment for prostate cancer.

RADIATION THERAPY Radiation therapy involves the use of high-energy x rays to kill cancer cells or to shrink tumors. It can be used instead of surgery for stage I and II cancer. The radiation can either be administered from a machine outside the body (external beam radiation), or small radioactive pellets can be implanted in the prostate gland in the area surrounding the tumor, called brachytherapy or interstitial implantation. Pellets containing radioactive iodine (I-125), palladium (Pd 103), or iridium (Ir 192) can be implanted on an outpatient basis, where they remain permanently. The radioactive effect of the seeds last only about a year.

The side effects of radiation can include inflammation of the bladder, rectum, and small intestine as well as disorders of blood clotting (coagulopathies). Impotence and incontinence are often delayed side effects of the treatment. A study indicated that bowel control problems were more likely after radiation therapy when compared to surgery, but impotence and incontinence were more likely after surgical treatment. Long-term results with radiation therapy are dependent on stage. A review of almost 1,000 patients treated with megavoltage irradiation showed 10-year survival rates to be significantly different by T-stage: T1 (79%), T2 (66%), T3 (55%), and T4 (22%). There does not appear to be a large difference in survival between external beam or interstitial treatments.

Hormone Therapy

Hormone therapy is commonly used when the cancer is in an advanced stage and has spread to other parts of the body, such as stage III or stage IV. Prostate cells need the male hormone testosterone to grow. Decreasing the levels of this hormone or inhibiting its activity will cause the cancer to shrink. Hormone levels can be decreased in several ways. Orchiectomy is a surgical procedure that involves complete removal of the testicles, leading to a decrease in the levels of testosterone. Another method tricks the body by administering the female hormone estrogen. When estrogen is given, the body senses the presence of a sex hormone and stops making the male hormone testosterone. However, there are some unpleasant side effects to hormone therapy. Men may have "hot flashes," enlargement and tenderness of the breasts, or impotence and loss of sexual desire, as well as blood clots, heart attacks, and strokes, depending on the dose of estrogen. Another side effect is osteoporosis, or loss of bone mass leading to brittle and easily fractured bones.

Watchful Waiting

Watchful waiting means no immediate treatment is recommended, but doctors keep the patient under careful observation. This is often done using periodic PSA tests. This option is generally used in older patients when the tumor is not very aggressive and the patients have other, more life-threatening, illnesses. Prostate cancer in older men tends to be slow-growing. Therefore, the risk of the patient dying from prostate cancer, rather than from other causes, is relatively small.

Alternative and Complementary Therapies

Alternative treatments that have been found helpful in coping with the emotional stress associated with prostate cancer include meditation, guided imagery, and relaxation techniques. Acupuncture is effective in relieving pain in some patients.

A variety of herbal products have been used to treat prostate cancer, including various compounds used in traditional Chinese medicine as well as single agents like Reishi mushrooms (Ganoderma lucidum). One herbal compound that was under investigation by the National Center for Complementary and Alternative Medicine (NCCAM) as a possible treatment for prostate cancer was PC-SPES, a mixture of eight herbs adapted from traditional Chinese medicine. In the summer of 2002, however, NCCAM put its studies of PC-SPES on hold when the Food and Drug Administration (FDA) determined that samples of the product were contaminated with undeclared prescription drug ingredients. PC-SPES was withdrawn from the American market in late 2002.

Coping With Cancer Treatment

The treatment process for prostate cancer can be a physically and emotionally exhausting time. Here are six general suggestions that can help make the process easier. Patients should:

  • put their faith and trust in their doctors once a treatment course has been chosen
  • remember that a patient is never without power and rights during the course of treatment
  • put practical affairs in order
  • closely monitor each step of the treatment
  • keep close family and friends informed and delegate responsibilities as necessary
  • work to make visits pleasant and comfortable
  • be careful to eat, sleep, exercise, and conduct daily activities in a healthy manner

Clinical Trials

Patients with extraprostatic disease are suitable candidates for clinical trials. One trial is the testing of a vaccine (GVAX) that causes the body to mount an immune response against all prostate cells. As the prostate is a nonessential organ, the destruction of the normal cells with the tumor cells is not a problem. The vaccine was made using cancer cells from a tumor that had been genetically engineered to express granulocyte/macro-phage colony-stimulating factor (GM-CSF), a potent activator of the entire immune system. The additional protein jumpstarted the immune response against the prostate cells upon vaccination and resulted in anti-tumor immune response.

Other trials for prostate cancer include evaluation of combination therapies, such as postoperative radiation delivery, use of cytotoxic agents, and hormonal treatment using luteinizing hormone-releasing hormone (LHRH) agonists and/or antiandrogens to shut down the growth of the hormone-dependent tumors. Other drugs that are being tested as of 2003 are chemoprotective agents like amifostine (Ethyol), which are given to prostate cancer patients to counteract the harmful side effects of radiation treatment.

Prevention

Because the cause of the cancer is not known, there is no definite way to prevent prostate cancer. Given its common occurrence and the low cost of screening, the American Cancer Society (ACS) and the National Comprehensive Cancer Network (NCCN) recommends that all men over age 40 have an annual rectal exam and that men have an annual PSA test beginning at age 50. African-American men and men with a family history of prostate cancer, who have a higher than average risk, should begin annual PSA testing even earlier, starting at age 45.

However, mandatory screening for prostate cancer is controversial. Because the cancer is so slow growing, and the side effects of the treatment can have significant impact on patient quality of life, some medical organizations question the wisdom of yearly exams. Some organizations have even noted that the effect of screening is discovering the cancer at an early stage when it may never grow to have any outward effect on the patient during this lifetime. Nevertheless, the NCI reports that the current aggressive screening methods have achieved a reduction in the death rate of prostate cancer of about 2.3% for African-Americans and about 4.6% for Caucasians since the mid-1990s, with a 20% increase in overall survival rate during that period.

A low-fat diet may slow the progression of prostate cancer. To reduce the risk or progression of prostate cancer, the American Cancer Society recommends a diet rich in fruits, vegetables and dietary fiber, and low in red meat and saturated fats.

Questions to Ask the Doctor

  • How do my age, general health, and other medical conditions affect my treatment choices?
  • What are the T, N, and M stages of my cancer and how do they influence my treatment options?
  • How do the Gleason score of my cancer and my blood prostate-specific antigen (PSA) level predict my outlook for survival and affect treatment options?
  • What are the likely side effects of each proposed therapy and how will they affect my quality of life?
  • What can be done to help manage the side effects of treatment?

Special Concerns

The availability of an early detection system for prostate cancer with the development of the PSA serum test has complicated the treatment of this disease. Early detection of an often slow-growing cancer, where treatment can significantly impact the quality of life of the patient, can be complicated. Long-term studies are currently in progress that should provide the first real quantitative information about the relative efficacy of the different treatment options, the actual occurrence of side effects, and the comparative benefits of watchful waiting treatment compared with more aggressive action.

Resources

Books

Beers, Mark H., MD, and Robert Berkow, MD, editors. "Prostate Cancer." Section 17, Chapter 233 In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

Carroll, Peter R., et al. "Cancer of the Prostate." In Cancer Principles and Practice of Oncology, edited by Devita, Vincent T., et al. Philadelphia: Lippincott Williams & Wilkins, 2001.

Wainrib, Barbara R., and Sandra Haber. Men, Women, and Prostate Cancer. Oakland, CA: New Harbinger Productions, Inc., 2000.

Periodicals

Alimi, D., C. Rubino, E. Pichard-Leandri, et al. "Analgesic Effect of Auricular Acupuncture for Cancer Pain: A Randomized, Blinded, Controlled Trial." Journal of Clinical Oncology 21 (November 15, 2003): 4120–4126.

Chang, S. S. "Exploring the Effects of Luteinizing Hormone-Releasing Hormone Agonist Therapy on Bone Health: Implications in the Management of Prostate Cancer." Urology 62 (December 22, 2003): 29–35.

de la Fouchardiere, C., A. Flechon, and J. P. Droz. "Coagulopathy in Prostate Cancer." Netherlands Journal of Medicine 61 (November 2003): 347–354.

Dziuk, T., and N. Senzer. "Feasibility of Amifostine Administration in Conjunction with High-Dose Rate Brachytherapy." Seminars in Oncology 30 (December 2003): 49–57.

Hsieh, K., and P. C. Albertsen. "Populations at High Risk for Prostate Cancer." Urological Clinics of North America 30 (November 2003): 669–676.

Linares, L. A., and D. Echols. "Amifostine and External Beam Radiation Therapy and/or High-Dose Rate Brachytherapy in the Treatment of Localized Prostate Carcinoma: Preliminary Results of a Phase II Trial." Seminars in Oncology 30 (December 2003): 58–62.

Sliva, D. "Ganoderma lucidum (Reishi) in Cancer Treatment." Integrative Cancer Therapies 2 (December 2003): 358–364.

Spetz, A. C., E. L. Zetterlund, E. Varenhorst, and M. Hammar. "Incidence and Management of Hot Flashes in Prostate Cancer." Journal of Supportive Oncology 1 (November-December 2003): 263–273.

Wilson, S. S., and E. D. Crawford. "Prostate Cancer Update." Minerva Urologica e Nefrologica 55 (December 2003): 199–204.

Organizations

The Association for the Cure of Cancer of the Prostate (CaPCure). 1250 Fourth St., Suite 360, Santa Monica, CA 90401. (800) 757-CURE. .

National Cancer Institute. Building 31, Room 10A31 31 Center Drive, MSC 2580, Bethesda, MD 20892-2580. (800) 4-CANCER. .

National Center for Complementary and Alternative Medicine (NCCAM) Clearinghouse. P. O. Box 7923, Gaithersburg, MD 20898. (888) 644-6226. .

Other

FDA MedWatch Safety Alert for PC-SPES, SPES, updated September 20, 2002. .

National Center for Complementary and Alternative Medicine (NCCAM). Recall of PC-SPES and SPES Dietary Supplements. NCCAM Publication No. D149, September 2002. .

—Lata Cherath, Ph.D.; Michelle Johnson, M.S., J.D.; Rebecca J. Frey, PhD

Dental Dictionary: prostate cancer
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n

A slowly progressive adenocarcinoma of the prostate gland that affects an increasing proportion of American males after the age of 50. It is the third leading cause of cancer deaths with more than 120,000 new cases reported in the United States each year.

Definition

Prostate cancer is a disease in which the cells of the prostate become abnormal and start to grow uncontrollably, forming tumors. Tumors that can spread to other parts of the body are called malignant tumors or cancers. Tumors incapable of spreading are said to be benign.

Description

Prostate cancer is the most common cancer among men in the United States, and is the second leading cause of cancer deaths. The American Cancer Society (ACS) estimates that in 1998, at least 185,000 new cases of prostate cancer will be diagnosed, and it will be the cause of at least 40,000 deaths. Although prostate cancer may be very slow-growing, it is a heterogeneous disease and can be quite aggressive, especially in younger men. When the disease is slow-growing, it may often go undetected. Because it may take many years for the cancer to develop, many men with the disease will probably die of other causes, rather than from the cancer itself.

Prostate cancer affects African American men twice as often as it does Caucasian men, and the mortality rate among African Americans is also two times higher. African Americans have the highest rate of prostate cancer in the world.

The prostate, testicles, and seminal vesicles are the major male sex glands. These three glands together secrete the fluid that makes up semen. The prostate is about the size of a walnut and lies just behind the urinary bladder. A tumor in the prostate interferes with proper control of the bladder and normal sexual functions. Often, the first symptom of prostate cancer to develop is difficulty in urinating. However, because the same symptom can be caused by a very common, noncancerous condition of the prostate (benign prostatic hyperplasia), it does not always mean that prostate cancer is present.

As the prostate cancer grows, some of the cells break off and spread to other parts of the body through the lymph or the blood. The most common sites to which it spreads are the lymph nodes, the lungs, and various bones around the hips and the pelvic region.

Causes & Symptoms

The cause of prostate cancer is not known, however, it is found mainly in men over the age of 55. The average age at diagnosis is 72. In fact, 80% of the prostate cancer cases occur in men over the age of 65. While only 1 in 100,000 men will get prostate cancer under the age of 40, the frequency rises to 1,326 cases in 100,000 for men between the ages of 70 and 74. Hence, age appears to be a risk factor for prostate cancer. Race may be another contributing factor, because African-Americans have the highest rate of prostate cancer in the world.

Some studies have shown that a family history of prostate cancer puts a man at a higher risk for developing this disease. In addition, there is some evidence to suggest that a diet high in fat increases the risk of prostate cancer. Workers in the electroplating and welding industries who are exposed to the metal cadmium and rubber industry workers appear to have a higher than average risk of getting this disease. Research has indicated that men with high plasma testosterone levels also may be at an increased risk.

Frequently, prostate cancer has no symptoms, and the disease is diagnosed when the patient goes for a routine screening examination. However, occasionally, when the tumor becomes large or the cancer has spread to the nearby tissues, the following symptoms may be seen:

  • weak or interrupted flow of the urine
  • frequent urination (especially at night)
  • difficulty starting urination
  • inability to urinate
  • pain or burning sensation when urinating
  • blood in the urine
  • persistent pain in lower back, hips, or thighs (bone pain)
  • painful ejaculation

Diagnosis

Prostate cancer is curable when detected early. However, because the early stages of prostate cancer may not have any visible symptoms, it often goes undetected until the patient goes for a routine physical examination. Diagnosis of the disease is made using some or all of the following tests.

Digital Rectal Examination (DRE)

In order to perform this test, the doctor puts a gloved, lubricated finger (digit) into the rectum to feel for any lumps in the prostate. The rectum lies just behind the prostate gland, and a majority of prostate tumors begin in the posterior region of the prostate. If the doctor does detect an abnormality, he or she may order more tests in order to confirm these findings.

BLOOD TESTS. Blood tests are used to measure the amounts of certain protein markers, such as prostate-specific antigen (PSA), found circulating in the blood. The cells lining the prostate generally make this protein and a small amount can be detected in the bloodstream. However, prostate cancers produce a lot of this protein, and it can be easily detected in the blood. Hence, when PSA is found in the blood in higher than normal amounts for the patient's particular age group, cancer may be present.

TRANSRECTAL ULTRASOUND. A small probe is placed in the rectum, and sound waves are released from the probe. These sound waves bounce off the prostate tissue and an image is created. Since normal prostate tissue and prostate tumors reflect the sound waves differently, the test can be used to detect tumors quite efficiently. Though the insertion of the probe into the rectum may be slightly uncomfortable, the procedure is generally painless and takes only 20 minutes.

PROSTATE BIOPSY. If cancer is suspected from the results of any of the above tests, the doctor will remove a small piece of prostate tissue with a hollow needle. This sample is then checked under the microscope for the presence of cancerous cells. Prostate biopsy is the most definitive diagnostic tool for prostate cancer.

If cancer is detected during the microscopic examination of the prostate tissue, the pathologist will "grade" the tumor using a method called the Gleason system. This means that he or she will score the tumor on a scale of 1–10 to indicate how aggressive the tumor is. Tumors with a lower score are less likely to grow and spread than are tumors with higher scores. The Gleason system is different from "staging" of the cancer. When a doctor stages a cancer, he or she gives it a number that indicates whether it has spread, as well as the extent of its spread. In Stage I, the cancer is localized in the prostate in one area, while in the last stage, Stage IV, the cancer cells have spread to other parts of the body.

X RAYS AND IMAGING TECHNIQUES. A chest x ray may be ordered to determine whether the cancer has spread to the lungs. Imaging techniques (such as computed tomography scans and magnetic resonance imaging), where a computer is used to generate a detailed picture of the prostate and areas nearby, may be done to get a clearer view of the internal organs. A bone scan also may be used to check whether the cancer has spread to the bone.

Treatment

The doctor and the patient will decide on the treatment mode after considering many factors. Such factors include the patient's age, the stage of the tumor, his general health, and the presence of any co-existing illnesses. In addition, the patient's personal preferences and the risks and benefits of each treatment protocol are also taken into account before any decision is made.

Various natural remedies used to treat noncancerous prostate problems can be implemented with the approval of a medical doctor along with the recommended medical care. Prostate enlargement is a precursor to prostate cancer, and many alternative treatments are available to alleviate benign prostate enlargement. Among those is the herb saw palmetto, which has shown to be highly effective in the treatment of prostate enlargement. In addition, treatments that focus on strengthening the immune system of the cancer patient can be helpful, using physiologic and psychologic therapies.

Lycopene, the antioxidant found in tomatoes and tomato products, has long been thought to help prevent prostate cancer. In the first clinical intervention trial of prostate cancer patients in 2001, lycopene supplementation slowed the progression of prostate camcer.

Visualization of a healthy, cancer-free body, and of cancer cells as weak and confused is believed to be healing imagery. Numerous studies affirm the power of a positive mental attitude in assisting conventional medical treatment to be more effective, while at the same time, minimizing undesirable side effects of chemotherapy or radiation.

Compounds contained in maitake mushrooms are believed to enhance the immune response and slow the growth of tumors. One study by a homeopathic physician, Dr. Abram Ber of Phoenix, Arizona, found that patients with prostate cancer treated with maitake mushroom tablets reported a decrease in the urge to urinate, along with improvement in the flow of urine.

Watchful Waiting

Watchful waiting means no immediate treatment is recommended, but doctors keep the patient under careful observation. This option is generally used in older patients when the tumor is not very aggressive and the patients have other, more life-threatening illnesses. Prostate cancer in older men tends to be slow-growing. Therefore, the risk of the patient dying from prostate cancer, rather than from other causes, is relatively small.

Allopathic Treatment

Surgery

For early stage prostate cancer, surgery is the best option and the most common one. Radical prostatectomy involves complete removal of the prostate. During the surgery, a sample of the lymph nodes near the prostate is removed to determine whether the cancer has spread beyond the prostate gland. Because the seminal vesicles (the glands where sperm is made) are removed along with the prostate, infertility is a side effect of this type of surgery. In order to minimize the risk of impotence (inability to have an erection) and incontinence (inability to control urine flow), a procedure known as "nervesparing" prostatectomy is used.

In a different surgical method, known as the transurethral resection procedure or TURP, only the cancerous portion of the prostate is removed, by using a small wire loop that is introduced into the prostate through the urethra. This technique is most often used in men who cannot have a radical prostatectomy due to age or other illness, and it is rarely recommended.

RADIATION THERAPY. Radiation therapy involves the use of high-energy x rays to kill cancer cells or to shrink tumors. It can be used instead of surgery for early stages of cancer. The radiation can either be administered from a machine outside the body (external beam radiation), or small radioactive pellets can be implanted in the prostate gland in the area surrounding the tumor.

HORMONE THERAPY. Hormone therapy is commonly used when the cancer is in an advanced stage and has spread to other parts of the body. Prostate cells need the male hormone testosterone to grow. Decreasing the levels of this hormone, or inhibiting its activity, will cause the cancer to shrink. Hormone levels can be decreased in several ways. Orchiectomy is a surgical procedure that involves complete removal of the testicles, leading to a decrease in the levels of testosterone. Alternatively, drugs (such as LHRH agonists or anti-androgens) that bind to the male hormone testosterone and block its activity can be given. Another method "tricks" the body by administering the female hormone estrogen. When this is given, the body senses the presence of a sex hormone and stops producing testosterone. However, there are some unpleasant side effects to hormone therapy. Depending on the doses of estrogen, men may have "hot flashes," enlargement and tenderness of the breasts, impotence or loss of sexual desire, as well as the risks of blood clots, heart attacks, and strokes.

CHEMOTHERAPY. Chemotherapy is the use of drugs to kill cancer cells. The drugs can either be taken as a pill or injected into the body through a needle that is inserted into a blood vessel. This type of treatment is called systemic treatment, because the drug enters the blood stream, travels through the whole body, and kills the cancer cells that are outside the prostate. Chemotherapy is sometimes used to treat prostate cancer that has recurred after other treatment. Further research is ongoing to find more drugs that are effective for the treatment of prostate cancer.

Expected Results

According to the American Cancer Society, the survival rate for all stages of prostate cancer combined has increased from 50–87% over the last 30 years. Due to early detection and better screening methods, nearly 60% of the tumors are diagnosed while they are still confined to the prostate gland. The five-year survival rate for early stage cancers is almost 99%. Sixty three percent of the patients survive 10 years, and 51% survive 15 years after initial diagnosis.

Prevention

Because the cause of the cancer is not known, there is no definite way to prevent prostate cancer. However, the American Cancer Society recommends that all men over age 40 have an annual rectal exam and that men have an annual PSA test beginning at age 50. Those who have a higher than average risk, including African American men and men with a family history of prostate cancer, should begin annual PSA testing even earlier, starting at age 45.

A diet low in fat may slow the progression of prostate cancer. Hence, in order to reduce the risk of prostrate cancer, the American Cancer Society recommends a diet rich in fruits, vegetables, and dietary fiber, and low in red meat and saturated fats. Intake of lycopene, which is found in cooked tomatoes or tomato sauce, is also thought to help reduce the risk of prostate cancer.

Resources

Books

Dollinger, Malin. Everyone's Guide to Cancer Therapy. Somerville House Books Limited, 1994.

Morra, Marion E. Choices. New York: Avon Books, 1994.

Wallner, Kent. Prostate Cancer: A Non-Surgical Perspective. Seattle: SmartMedicine Press, 996.

Periodicals

"Clinical Intervention Trial Finds Benefit of Lycopene." Cancer Weekly (November 27, 2001) :38.

Organizations

American Cancer Society. 1599 Clifton Road NE, Atlanta, Georgia 30329. (800) 227–2345.

American Urologic Association. 1120 N. Charles Street, Baltimore, MD 21201. (410) 223–4310.

Cancer Research Institute. 681 Fifth Avenue, New York, N.Y. 10022. (800) 992–2623.

National Institutes of Health. National Cancer Institute. 9000 Rockville Pike, Bethesda, MD 20892. (800)422–6237.

National Institute on Aging Information Center. (800) 222–2225.

Zero — The Project to End Prostate Cancer. 1300 19th Street NW, Suite 400, Washington DC 20036. (202)842–3600 ext. 214.

[Article by: Kathleen Wright; Teresa G. Odle]

Encyclopedia of Public Health: Prostate Cancer
Top

Prostate cancer is the most common cancer in men and the second leading cause of cancer-related death in men. An estimated 191,000 cases of prostate cancer will be diagnosed in 2001 in the United States along with 30,500 prostate cancer-related deaths. The disease is detected by a combination of abnormal serum prostate-specific antigen (PSA) and digital rectal exam (DRE), and less often as an incidental finding after prostate resection for obstructive benign disease. It is uncommon at this time to diagnose prostate cancer in association with gross urinary obstruction, bleeding, or unexplained skeletal pain.

The disease is both hereditary and sporadic with one gene (HPC2), and several gene loci recently identified. The risk for developing prostate cancer increases twofold if a first-degree relative is affected and it further increases as more family members are afflicted (first- and second-degree relatives). Although no specific cause for prostate cancer has been identified, several factors contribute to the development of the disease. This includes the level of saturated animal fat in the diet, vitamin D production, and ethnic origin. African Americans have the highest rate of prostate cancer in the world, while it is the lowest in native Asians. The disease is more commonly seen after the age of fifty.

The natural history of prostate cancer is strongly driven by the tumor grade. The risk of prostate cancer death is low (less than 10%) in patients of almost all ages with low-grade disease; however, it is substantial for patients with moderate- or high-grade disease. Metastatic disease has a very predictable natural history, with a median survival of thirty to thirty-three months after diagnosis.

Prostate cancer is generally detected by an abnormal serum PSA determination and/or an abnormal DRE. The diagnosis is generally made by an ultrasound-guided needle biopsy of the prostate. These techniques have led to a stage shift in the disease, with the majority of lesions now detected in the clinically localized state. Contemporary treatments for clinically localized disease include watchful waiting, radical prostatectomy, radiation therapy (external beam or brachytherapy), or cryosurgery. Androgen ablation (removal of testosterone-like substances from the system) can be used alone or in combination with other modalities, and is the principle form of therapy for advanced disease.

The decision whether to treat the disease or observe the patient should be based on the probability of the patient reasonably living another five to ten years, and thus takes into account the patient's age and comorbid conditions. Surgery can be very effective and is generally employed in younger men where nerve-sparing surgery can be used to preserve erectile function. The major side effect is urinary incontinence, which can be significant in a small percentage of patients. External beam radiation therapy is also a standard form of therapy which is generally performed in older patients (over age seventy). It is usually well tolerated, but a small percentage of men can develop gastrointestinal side effects related to rectal irritation.

Brachytherapy refers to the implantation of radioactive pellets in the prostate gland, usually under ultrasound guidance. This technique has been employed for approximately a decade and is an effective form of therapy in men with appropriate lesions. The major side effect from this therapy is an increase in irritative voiding symptoms. An increasing body of knowledge suggests that the addition of androgen ablation may improve the outcomes of patients receiving radiation.

Approximately 20 percent of patients treated for localized disease will experience a rise in their PSA within five years. This group of biochemical- failure patients are an enlarging cohort of patients for which exact treatment recommendations are not available. Gross loco-regional disease has become less common in the PSA era. Prostate cancer generally metastasizes to the lymph nodes and the bones, with less common involvement of the visceral organs.

Prostate tumors are classically dependent on endogenous androgens as growth factors. The removal of androgens by castration (surgical or chemical) results in a regression of symptoms and measurable disease in 80 percent of patients. Unfortunately, there are androgen-resistant clones in most tumors, which makes this form of therapy palliative. Androgen ablation can be performed by the removal of the testicles or the administration of a luteinizing hormone releasing hormone (LHRH) antagonist.

Prostate cancer relapsing after androgen ablation is designated androgen independent prostate cancer. The median survival for such patients is approximately eleven months. Although newer chemotherapy agents are displaying activity in advanced prostate cancer, treatment is generally palliative. This is an area of intense clinical investigation and protocol therapy.

(SEE ALSO: Cancer; Prostate-Specific Antigen [PSA])

Bibliography

Albertson, P. C.; Hanley, J. A.; Gleason, D. R. et al. (1998). "Competing Risk Analysis of Men Aged 55 to 74 Years at Diagnosis Managed Conservatively for Clinically Localized Prostate Cancer." Journal of the American Medical Association 280:975–980.

Catalona, W. J., and Smith, D. S. (1998). "Cancer Recurrence and Survival Rates after Anatomic Radical Retropubic Porstatectomy for Prostate Cancer: Intermediate-Term Results." Journal of Urology 160:2428–2434.

D'Amico, A. V.; Whittington, R.; Malkowicz, S. B. et al. (1998). "Biochemical Outcome after Radical Prostatectomy, External Beam Radiation Therapy or Interstitial Radiation Therapy for Clinically Localized Prostate Cancer." Journal of the American Medical Association 280:969–974.

Eisenberg, M. A.; Blumenstein, B. A.; Crawford, E. D. et al. (1998). "Bilateral Orchiectomy with or without Flutamide for Metastatic Prostate Cancer." New England Journal of Medicine 339:1036–1042.

Powel, I. J. (1998). "Prostate Cancer in the African-American: Is This a Different Disease?" Seminars in Urologic Oncology 16:221–226.

Ragde, H.; Blasko, J. C.; Grimm, P. D. et al. (1997). "Interstital Iodine-125 Radiation without Adjuvant Therapy in the Treatment of Clinically Localized Prostate Carcinoma." Cancer 80:442–453.

— S. BRUCE MALKOWICZ



 
Columbia Encyclopedia: prostate cancer
Top
prostate cancer, cancer originating in the prostate gland. Prostate cancer is the leading malignancy in men in the United States and is second only to lung cancer as a cause of cancer death in men. It occurs predominantly in older men; the median age at diagnosis is 72 years. Black men have a higher incidence than white men. The cause of prostate cancer is unknown, but the incidence varies markedly by geographic region, an indication that there are environmental factors that may trigger the disease. For example, men in China and Japan have a low rate of prostate cancer, but the incidence rises in Chinese and Japanese men who move to the United States. The hormone testosterone is believed to have a role in the development of prostate cancer, and studies have shown a relationship between high dietary fat intake and increased testosterone levels. Prostate tumors are often slow growing. Around 95% are classified as adenocarcinomas (arising from epithelial glandular tissue). The most common site of metastasis is the bone.

Screening and Diagnosis

Traditionally, prostate cancer screening consisted of digital-rectal examination. Since 1986, however, a blood test for a tumor marker called prostate-specific antigen (PSA) has greatly increased the number of early-stage prostate cancers diagnosed. An elevated level of PSA can indicate the presence of prostatic malignancy. Elevated PSA is further investigated by an ultrasound test and needle biopsy, in which a fine needle is inserted into the gland and cells are extracted for laboratory analysis. In some cases a bone scan is also performed to rule out metastatic disease. Because PSA tests detect not only aggressive cancers but slow-growing cancers that are not life-threatening, many people disagree with routine PSA testing of asymptomatic men, fearing that the test might lead to unnecessary anxiety or treatments that compromise quality of life without assuring a longer life than a man ignorant of his condition would enjoy.

Treatment

For most patients with localized tumors, surgical removal of the prostate gland (prostatectomy) is the initial treatment, despite possible side effects of urinary incontinence and impotence. Localized prostate cancer can often be cured. After surgery, a repeated blood test for protein-specific antigen can indicate whether any cancer remains. In metastatic disease, other treatments are employed depending on the stage of the disease and the age and health of the patient. Treatment options include external-beam radiation, implantation of radioactive isotopes, and palliative surgery. Hormonal manipulation by giving estrogens or other drugs, or by orchiectomy (removal of the testes), is sometimes used to decrease levels of testosterone. Very small cancers or slow-growing cancers in older men are sometimes watched, but not treated, without compromising life expectancy. Experimental treatments under investigation include cryosurgery, destroying the tumor by freezing.

Bibliography

See M. Korda, Man to Man (1996), and P. Walsh and J. F. Worthington, Dr. Patrick Walsh's Guide to Surviving Prostate Cancer (2001). See also publications of the National Cancer Institute and the American Cancer Society.


Wikipedia: Prostate cancer
Top
Prostate cancer
Classification and external resources
ICD-10 C61.
ICD-9 185
OMIM 176807
DiseasesDB 10780
MedlinePlus 000380
eMedicine radio/574
MeSH D011471

Prostate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. The cancer cells may metastasize (spread) from the prostate to other parts of the body, particularly the bones and lymph nodes. Prostate cancer may cause pain, difficulty in urinating, problems during sexual intercourse, or erectile dysfunction. Other symptoms can potentially develop during later stages of the disease.

Contents

Overview

Rates of detection of prostate cancers vary widely across the world, with South and East Asia detecting less frequently than in Europe, and especially the United States.[1] Prostate cancer tends to develop in men over the age of fifty and although it is one of the most prevalent types of cancer in men, many never have symptoms, undergo no therapy, and eventually die of other causes. This is because cancer of the prostate is, in most cases, slow-growing, symptom free and men with the condition often die of causes unrelated to the prostate cancer, such as heart/circulatory disease, pneumonia, other unconnected cancers, or old age. Many factors, including genetics and diet, have been implicated in the development of prostate cancer. The presence of prostate cancer may be indicated by symptoms, physical examination, prostate specific antigen (PSA), or biopsy. There is controversy about the accuracy of the PSA test and the value of screening. Suspected prostate cancer is typically confirmed by taking a biopsy of the prostate and examining it under a microscope. Further tests, such as CT scans and bone scans, may be performed to determine whether prostate cancer has spread.

Treatment options for prostate cancer with intent to cure are primarily surgery and radiation therapy. Other treatments such as hormonal therapy, chemotherapy, proton therapy, cryosurgery, high intensity focused ultrasound (HIFU) also exist depending on the clinical scenario and desired outcome.

The age and underlying health of the man, the extent of metastasis, appearance under the microscope, and response of the cancer to initial treatment are important in determining the outcome of the disease. The decision whether or not to treat localized prostate cancer (a tumor that is contained within the prostate) with curative intent is a patient trade-off between the expected beneficial and harmful effects in terms of patient survival and quality of life.

Prostate

Prostatelead.jpg

The prostate is a part of the male reproductive organ that helps make and store seminal fluid. In adult men, a typical prostate is about three centimeters long and weighs about twenty grams.[2] It is located in the pelvis, under the urinary bladder and in front of the rectum. The prostate surrounds part of the urethra, the tube that carries urine from the bladder during urination and semen during ejaculation.[3] Because of its location, prostate diseases often affect urination, ejaculation, and rarely defecation. The prostate contains many small glands which make about twenty percent of the fluid constituting semen.[4] In prostate cancer, the cells of these prostate glands mutate into cancer cells. The prostate glands require male hormones, known as androgens, to work properly. Androgens include testosterone, which is made in the testes; dehydroepiandrosterone, made in the adrenal glands; and dihydrotestosterone, which is converted from testosterone within the prostate itself. Androgens are also responsible for secondary sex characteristics such as facial hair and increased muscle mass.

An important part of evaluating prostate cancer is determining the stage, or how far the cancer has spread. Knowing the stage helps define prognosis and is useful when selecting therapies. The most common system is the four-stage TNM system (abbreviated from Tumor/Nodes/Metastases). Its components include the size of the tumor, the number of involved lymph nodes, and the presence of any other metastases.

The most important distinction made by any staging system is whether or not the cancer is still confined to the prostate. In the TNM system, clinical T1 and T2 cancers are found only in the prostate, while T3 and T4 cancers have spread elsewhere. Several tests can be used to look for evidence of spread. These include computed tomography to evaluate spread within the pelvis, bone scans to look for spread to the bones, and endorectal coil magnetic resonance imaging to closely evaluate the prostatic capsule and the seminal vesicles. Bone scans should reveal osteoblastic appearance due to increased bone density in the areas of bone metastasis--opposite to what is found in many other cancers that metastasize.

Computed tomography (CT) and magnetic resonance imaging (MRI) currently do not add any significant information in the assessment of possible lymph node metastases in patients with prostate cancer according to a meta-analysis.[5] The sensitivity of CT was 42% and specificity of CT was 82%. The sensitivity of MRI was 39% and the specificity of MRI was 82%. For patients at similar risk to those in this study (17% had positive pelvic lymph nodes in the CT studies and 30% had positive pelvic lymph nodes in the MRI studies), this leads to a positive predictive value (PPV) of 32.3% with CT, 48.1% with MRI, and negative predictive value (NPV) of 87.3% with CT, 75.8% with MRI.

After a prostate biopsy, a pathologist looks at the samples under a microscope. If cancer is present, the pathologist reports the grade of the tumor. The grade tells how much the tumor tissue differs from normal prostate tissue and suggests how fast the tumor is likely to grow. The Gleason system is used to grade prostate tumors from 2 to 10, where a Gleason score of 10 indicates the most abnormalities. The pathologist assigns a number from 1 to 5 for the most common pattern observed under the microscope, then does the same for the second-most-common pattern. The sum of these two numbers is the Gleason score. The Whitmore-Jewett stage is another method sometimes used. Proper grading of the tumor is critical, since the grade of the tumor is one of the major factors used to determine the treatment recommendation.[citation needed]

Symptoms

Early prostate cancer usually causes no symptoms. Often it is diagnosed during the workup for an elevated PSA noticed during a routine checkup. It's highly advised to avoid sexual intercourse for 3 days prior to a PSA test because that does affect the outcome of the test. Sometimes, however, prostate cancer does cause symptoms, often similar to those of diseases such as benign prostatic hypertrophy. These include frequent urination, increased urination at night, difficulty starting and maintaining a steady stream of urine, blood in the urine, and painful urination. Prostate cancer is associated with urinary dysfunction as the prostate gland surrounds the prostatic urethra. Changes within the gland, therefore, directly affect urinary function. Because the vas deferens deposits seminal fluid into the prostatic urethra, and secretions from the prostate gland itself are included in semen content, prostate cancer may also cause problems with sexual function and performance, such as difficulty achieving erection or painful ejaculation.[6]

Advanced prostate cancer can spread to other parts of the body, possibly causing additional symptoms. The most common symptom is bone pain, often in the vertebrae (bones of the spine), pelvis, or ribs. Spread of cancer into other bones such as the femur is usually to the proximal part of the bone. Prostate cancer in the spine can also compress the spinal cord, causing leg weakness and urinary and fecal incontinence.[7]

Causes

The specific causes of prostate cancer remain unknown.[8] A man's risk of developing prostate cancer is related to his age, genetics, race, diet, lifestyle, medications, and other factors. The primary risk factor is age. Prostate cancer is uncommon in men younger than 45, but becomes more common with advancing age. The average age at the time of diagnosis is 70.[9] However, many men never know they have prostate cancer. Autopsy studies of Chinese, German, Israeli, Jamaican, Swedish, and Ugandan men who died of other causes have found prostate cancer in thirty percent of men in their 50s, and in eighty percent of men in their 70s.[10] In the year 2005 in the United States, there were an estimated 230,000 new cases of prostate cancer and 30,000 deaths due to prostate cancer.[11]

Genetics

A man's genetic background contributes to his risk of developing prostate cancer. This is suggested by an increased incidence of prostate cancer found in certain racial groups, in identical twins of men with prostate cancer, and in men with certain genes. In the United States, prostate cancer more commonly affects black men than white or Hispanic men, and is also more deadly in black men.[12] Men who have a brother or father with prostate cancer have twice the usual risk of developing prostate cancer.[13] Studies of twins in Scandinavia suggest that forty percent of prostate cancer risk can be explained by inherited factors.[14] However, no single gene is responsible for prostate cancer; many different genes have been implicated. Two genes (BRCA1 and BRCA2) that are important risk factors for ovarian cancer and breast cancer in women have also been implicated in prostate cancer.[15]

Diet

Dietary amounts of certain foods, vitamins, and minerals can contribute to prostate cancer risk. Dietary factors that may decrease prostate cancer risk include the mineral selenium[16][17]. A study in 2007 cast doubt on the effectiveness of lycopene (found in tomatoes) in reducing the risk of prostate cancer.[18] Lower blood levels of vitamin D also may increase the risk of developing prostate cancer. This may be linked to lower exposure to ultraviolet (UV) light, since UV light exposure can increase vitamin D in the body.[19]

A large study has implicated dairy, specifically low-fat milk and other dairy products to which vitamin A palmitate has been added. This form of synthetic vitamin A has been linked to prostate cancer because it reacts with zinc and protein to form an unabsorbable complex.[citation needed]

Medication exposure

There are also some links between prostate cancer and medications, medical procedures, and medical conditions. Daily use of anti-inflammatory medicines such as aspirin, ibuprofen, or naproxen may decrease prostate cancer risk.[20] Use of the cholesterol-lowering drugs known as the statins may also decrease prostate cancer risk.[21] Infection or inflammation of the prostate (prostatitis) may increase the chance for prostate cancer. In particular, infection with the sexually transmitted infections chlamydia, gonorrhea, or syphilis seems to increase risk.[22] Finally, obesity[23] and elevated blood levels of testosterone[24] may increase the risk for prostate cancer.

Research released in May 2007, found that US war veterans who had been exposed to Agent Orange had a 48% increased risk of prostate cancer recurrence following surgery.[25]

Potential viral cause

Findings published in the Proceedings of the National Academy of Sciences (2009) found Xenotropic MuLV-related virus or XMRV protein expression in 23 percent of human prostate tumors. [26] However a more recent large study from Germany failed to find any XMRV-specific sequences in the DNA or RNA of samples from 589 prostate cancer patients, and none of the samples contained XMRV-specific antibodies.[27].

Pathophysiology

When normal cells are damaged beyond repair, they are eliminated by apoptosis. Cancer cells avoid apoptosis and continue to multiply in an unregulated manner.

Prostate cancer is classified as an adenocarcinoma, or glandular cancer, that begins when normal semen-secreting prostate gland cells mutate into cancer cells. The region of prostate gland where the adenocarcinoma is most common is the peripheral zone. Initially, small clumps of cancer cells remain confined to otherwise normal prostate glands, a condition known as carcinoma in situ or prostatic intraepithelial neoplasia (PIN). Although there is no proof that PIN is a cancer precursor, it is closely associated with cancer. Over time, these cancer cells begin to multiply and spread to the surrounding prostate tissue (the stroma) forming a tumor. Eventually, the tumor may grow large enough to invade nearby organs such as the seminal vesicles or the rectum, or the tumor cells may develop the ability to travel in the bloodstream and lymphatic system. Prostate cancer is considered a malignant tumor because it is a mass of cells that can invade other parts of the body. This invasion of other organs is called metastasis. Prostate cancer most commonly metastasizes to the bones, lymph nodes, rectum, and bladder.

Diagnosis

The only test that can fully confirm the diagnosis of prostate cancer is a biopsy, the removal of small pieces of the prostate for microscopic examination. However, prior to a biopsy, several other tools may be used to gather more information about the prostate and the urinary tract. Cystoscopy shows the urinary tract from inside the bladder, using a thin, flexible camera tube inserted down the urethra. Transrectal ultrasonography creates a picture of the prostate using sound waves from a probe in the rectum.

Biopsy

If cancer is suspected, a biopsy is offered. During a biopsy a urologist or radiologist obtains tissue samples from the prostate via the rectum. A biopsy gun inserts and removes special hollow-core needles (usually three to six on each side of the prostate) in less than a second. Prostate biopsies are routinely done on an outpatient basis and rarely require hospitalization. Fifty-five percent of men report discomfort during prostate biopsy. [28]

Gleason score

The tissue samples are then examined under a microscope to determine whether cancer cells are present, and to evaluate the microscopic features (or Gleason score) of any cancer found.

Tumor markers

Tissue samples can be stained for the presence of PSA and other tumor markers in order to determine the origin of maligant cells that have metastasized.[29]

Diagnostic tools under investigation

At present, an active area of research involves non-invasive methods of prostate tumor detection. Adenoviruses modified to transfect tumor cells with harmless yet distinct genes (such as luciferase) have proven capable of early detection. So far, however, this area of research has been tested only in animal and LNCaP models.[30]

PCA3

Another potential non-invasive method of early prostate tumor detection is through a molecular test that detects the presence of cell-associated PCA3 mRNA in urine. PCA3 mRNA is expressed almost exclusively by prostate cells and has been shown to be highly over-expressed in prostate cancer cells. PCA3 is not a replacement for PSA but an additional tool to help decide whether, in men suspected of having prostate cancer, a biopsy is really needed. The higher the expression of PCA3 in urine, the greater the likelihood of a positive biopsy, i.e., the presence of cancer cells in the prostate.

Early prostate cancer

It was reported in April 2007 that a new blood test for early prostate cancer antigen-2 (EPCA-2) that may alert men if they have prostate cancer and how aggressive it will be is being researched.[31][32]

Prostate mapping

Prostate mapping is a method of diagnosis that may be accurate in determining the precise location and aggressiveness of a tumor. It uses a combination of multi-sequence MRI imaging techniques and a template-guided biopsy system, and involves taking multiple biopsies through the skin that lies in front of the rectum rather than through the rectum itself. The procedure is carried out under general anesthetic.[33]

Prostasomes

Epithelial cells of the prostate secrete prostasomes as well as PSA. Prostasomes are membrane–surrounded, prostate-derived organelles that appear extracellularly, and one of their physiological functions is to protect the sperm from attacks by the female immune system. Cancerous prostate cells continue to synthesize and secrete prostasomes, and may be shielded against immunological attacks by these prostasomes. Research of several aspects of prostasomal involvement in prostate cancer has been performed.[34]

Prevention

Food, vitamins and medication

Evidence from epidemiological studies supports a possible protective role in reducing prostate cancer for dietary selenium, vitamin E, lycopene, and soy foods. High plasma levels of Vitamin D may also have a protective effect.[35] Estrogens from fermented soybeans and other plant sources (called phytoestrogens) may also help prevent prostate cancer.[36] The selective estrogen receptor modulator drug toremifene has shown promise in early trials.[37][38] Two medications which block the conversion of testosterone to dihydrotestosterone, finasteride[39] and dutasteride,[40] have also shown some promise. The use of these medications for primary prevention is still in the testing phase, and they are not widely used for this purpose. The initial problem with these medications is that they may preferentially block the development of lower-grade prostate tumors, leading to a relatively greater chance of higher grade cancers, and negating any overall survival improvement. More recent research found that finasteride did not increase the percentage of higher grade cancers. A 2008 study update found that finasteride reduces the incidence of prostate cancer by 30%. In the original study it turns that that the smaller prostate caused by finasteride means that a doctor is more likely to hit upon cancer nests and more likely to find aggressive-looking cells. Most of the men in the study who had cancer — aggressive or not — chose to be treated and many had their prostates removed. A pathologist then carefully examined every one of those 500 prostates and compared the kinds of cancers found at surgery to those initially diagnosed at biopsy. Finasteride did not increase the risk of High-Grade prostate cancer.[41][42]

Green tea may be protective (due to its polyphenol content),[43] although the most comprehensive clinical study indicates that it has no protective effect.[44] A 2006 study of green tea derivatives demonstrated promising prostate cancer prevention in patients at high risk for the disease.[45] Recent research published in the Journal of the National Cancer Institute suggests that taking multivitamins more than seven times a week can increase the risks of contracting the disease.[46][47] This research was unable to highlight the exact vitamins responsible for this increase (almost double), although they suggest that vitamin A, vitamin E and beta-carotene may lie at its heart. It is advised that those taking multivitamins never exceed the stated daily dose on the label. Scientists recommend a healthy, well balanced diet rich in fiber, and to reduce intake of meat.[citation needed] A 2007 study published in the Journal of the National Cancer Institute found that men eating cauliflower, broccoli, or one of the other cruciferous vegetables, more than once a week were 40% less likely to develop prostate cancer than men who rarely ate those vegetables.[48][49] The phytochemicals indole-3-carbinol and diindolylmethane, found in cruciferous vegetables, has antiandrogenic and immune modulating properties.[50][51]

A comprehensive worldwide report Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective compiled by World Cancer Research Fund and American Institute for Cancer Research reports that there is significant relation between lifestyle (including food consumption) and cancer prevention.

Ejaculation frequency

More frequent ejaculation also may decrease a man's risk of prostate cancer. One study showed that men who ejaculated five times a week in their 20s had a decreased rate of prostate cancer, though other studies have shown no benefit.[52][53] The results contradict those of previous studies, which have suggested that having had many sexual partners, or a high frequency of sexual activity, increases the risk of prostate cancer by up to 40 percent. The key difference is that these earlier studies defined sexual activity as sexual intercourse, whereas this study focused on the number of ejaculations, whether or not intercourse was involved.[54] Another study completed in 2004 reported that "Most categories of ejaculation frequency were unrelated to risk of prostate cancer. However, high ejaculation frequency was related to decreased risk of total prostate cancer." The report abstract concluded, "Our results suggest that ejaculation frequency is not related to increased risk of prostate cancer." [55] A 2008 study showed that men who engaged in frequent masturbation, of about two to seven times a week, at the ages of 20s and 30s, had a higher rate of prostate cancer, while men who engaged in frequent masturbation, once a week, at the age of 50s had a lower rate.[56]

Oils and fatty acids

In experimental models using mice have been tested, dietary and serum omega-6 polyunsaturated fatty acids (PUFAs) increased prostate tumor growth,and has sped up histopathological progression, and decreased survival, while the omega-3 fatty acids, in the same situation, had the opposite, beneficial effect.[57]

Men with higher serum levels of the short-chain omega-6 fatty acid linoleic acid have higher rates of prostate cancer.[58] However, men with high serum linoleic acid, but not palmitic, can reduce the risk of prostate cancer by taking tocopherol supplementation.[59]

Men with elevated levels of long-chain omega-3 fatty acids (EPA and DHA) had lowered incidence.[58]

A long-term study reports that "blood levels of trans fatty acids, in particular trans fats resulting from the hydrogenation of vegetable oils, are associated with an increased prostate cancer risk."[60]

Some researchers have indicated that serum myristic acid[59][61] and palmitic acid[61] and dietary myristic[62] and palmitic[62] saturated fatty acids and serum palmitic combined with alpha-tocopherol supplementation[59] are associated with increased risk of prostate cancer in a dose-dependent manner. Serum association of these and other saturated fatty acids was also investigated by another study.[61]

The American Dietetic Association and Dieticians of Canada report a decreased incidence of prostate cancer for those following a vegetarian diet.[63]

Screening

Prostate cancer screening is an attempt to find unsuspected cancers. Screening tests may lead to more specific follow-up tests such as a biopsy, where small cores of the prostate are removed for closer study. Prostate cancer screening options include the digital rectal exam and the prostate-specific antigen (PSA) blood test. Screening for prostate cancer is controversial because it is expensive and is not at all clear whether the benefits of screening outweigh the risks of follow-up diagnostic tests and cancer treatments and the unnecessary worry for the patient that often ensues.

Prostate cancer is usually a slow-growing cancer, very common among older men. In fact, most prostate cancers never grow to the point where they cause symptoms, and most men with prostate cancer die of other causes before prostate cancer has an impact on their lives. The PSA screening test may detect these small cancers that would never become life-threatening. Doing the PSA test in these men may lead to overdiagnosis, including additional testing and treatment. Follow-up tests, such as prostate biopsy, may cause pain, bleeding and infection. Prostate cancer treatments may cause urinary incontinence and erectile dysfunction. A large randomized study in which 76,000 men were randomized to receive either PSA screening or conventional care found that more men that underwent PSA screening were diagnosed with prostate cancer, but that there was no difference in mortality between the two groups. [64]

The results from two of the largest randomized trials regarding the efficacy of screening have now been published. [65] In one of these trials, the death rate from prostate cancer was actually higher in the group that had total screening compared to the control group that had only normal rates of screening. The other showed some benefit from screening, but the reduction in deaths was minor compared to the level of intervention needed to prevent it.

In the European Randomized Study of Screening for Prostate Cancer initiated in the early 1990s, the intention was to evaluate the effect of screening with prostate-specific antigen (PSA) testing on death rates from prostate cancer. The trial involved 182,000 men between the ages of 50 and 74 years in seven European countries randomly assigned to a group that was offered PSA screening at an average of once every 4 years or to a control group that did not receive such screening. During a median follow-up of almost 9 years, the cumulative detected incidence of prostate cancer was 820 per 10,000 in the screening group and 480 per 10,000 in the control group. Deaths from these cancers in this time was much lower. There were 214 prostate cancer deaths in the screening group and 326 in the control group, a difference of 71 men per 10,000 in the tested group compared to the control. The researchers concluded that PSA-based screening did reduce the rate of death from prostate cancer by 20%, but that this was associated with a high risk of overdiagnosis, which means that 1410 men would need to be screened and 48 additional cases of prostate cancer would need to be treated to prevent just one death from prostate cancer. [66]

A US study looked at the general effectiveness of a screening program involving both PSA and DRE methods. This was conducted between 1993 thu 2001, in which 76,693 men at 10 U.S. study centers 38,343 subjects received screening (an annual PSA testing for 6 years and DRE for 4 years) and a control group of 38,350 subjects reveived 'usual care' with subjects and healthcare providers receiving the results and deciding on the type of follow-up evaluation. 'Usual care' means that some in this group would have received some screening, as some organizations have recommended. After 7 years of follow-up, the incidence of prostate cancer per 10,000 person-years was 116 (2,820 cancers) in the screening group and 95 (2,322 cancers) in the control group. The incidence of death attributed to prostate cancer per 10,000 person-years was 2.0 (50 deaths) in the screening group and 1.7 (44 deaths) in the control group (rate ratio, 1.13; 95% CI, 0.75 to 1.70). The data at 10 years were 67% complete and consistent with these overall findings. The researchers concluded that, after 7 to 10 years of follow-up, the rate of death from prostate cancer was very low and did not differ significantly between the two study groups.[67]

Commenting on the findings, the Chief Medical Officer of the American Cancer Society, Otis W. Brawley, MD, said

many experts had anticipated these studies would show a small number of men will benefit from prostate screening, but a large number of men will be treated unnecessarily. And that's what these studies show. However, the question is not as simple as: 'does prostate cancer screening work?' What we need to know is: what are benefits of prostate cancer screening and are they large enough to outweigh the harms associated with it? And, despite the release of this early data, we still cannot say whether the benefits outweigh the risk.[68]"

His Deputy chief medical officer, Len Lichtenfeld, MD, MACP said

"When one considers all of the problems associated with treatment for prostate cancer -- urine incontinence, impotence, pain and bleeding among others -- that is a lot of men left with a lot of symptoms to save one life."

The American Urological Association said that "The decision to screen is one that a man should make in conjunction with his physician, and should incorporate known prostate cancer risk factors, such as family history of prostate cancer, age, ethnicity/race, and whether or not a man has had a previous negative prostate biopsy. These factors are different for every man and, therefore, the benefits of screening should be considered in the broader perspective."[69] The organization will review its best practice guidelines later this year.

  • The 2008 recommendations of the U.S. Preventive Services Task Force (USPSTF) concluded that routine screening for prostate cancer using PSA testing or digital rectal examination (DRE) was not recommended for men over 75 and that the evidence was insufficient to recommend for or against screening for men under 75 years old.[70] The previous 1995 USPSTF recommendation was against routine screening.
  • The American Cancer Society (ACS) has recently updated its guidelines making cleat that it does not recommend routine prostate cancer screening for all men.[71]. It recommends that the risks and benefits of scrrening need to be weighed, and discusssions should start early for those in high risk groups. Screening should take place only wíth informed consent of the patient in full knowledge of both benefits and risks. The revised guidlines reflect the concerns about the potentially down-played risks and over-blown claims for the success of prostate cancer screening.[72][73]
The American Cancer Society (ACS) does not support routine testing for prostate cancer at this time. ACS does believe that health care professionals should discuss the potential benefits and limitations of prostate cancer early detection testing with men before any testing begins. This discussion should include an offer for testing with the prostate-specific antigen (PSA) blood test and digital rectal exam (DRE) yearly, beginning at age 50, to men who are at average risk of prostate cancer and have at least a 10-year life expectancy. Following this discussion, those men who favor testing should be tested. Men should actively take part in this decision by learning about prostate cancer and the pros and cons of early detection and treatment of prostate cancer. This discussion should take place starting at age 45 for men at high risk of developing prostate cancer. This includes African American men and men who have a first-degree relative (father, brother, or son) diagnosed with prostate cancer at an early age (younger than age 65). This discussion should take place at age 40 for men at even higher risk (those with several first-degree relatives who had prostate cancer at an early age). If, after this discussion, a man asks his health care professional to make the decision for him, he should be tested (unless there is a specific reason not to test). [71]
  • The 2007 National Comprehensive Cancer Network (NCCN) guideline recommends offering a baseline PSA test and DRE at ages 40 and 45 and annual PSA testing and DRE beginning at age 50 (with annual PSA testing and DRE beginning at age 40 for African-American men, men with a family history of prostate cancer, and men with a PSA ≥ 0.6 ng/mL at age 40 or PSA > 0.6 ng/mL at age 45) through age 80, along with information on the risks and benefits of screening. Biopsy is recommended if DRE is positive or PSA ≥ 4 ng/mL, and biopsy considered if PSA > 2.5 ng/mL or PSA velocity ≥ 0.35 ng/mL/year when PSA ≤ 2.5 ng/mL.[74]
  • Some U.S. radiation oncologists and medical oncologists who specialize in treating prostate cancer recommend obtaining a baseline PSA in all men at age 35[75] or beginning annual PSA testing in high risk men at age 35.[76]
  • The American Urological Association Patient Guide to Prostate Cancer.[77]

Since there is no general agreement that the benefits of PSA screening outweigh the harms, the consensus is that clinicians use a process of shared decision-making that includes discussing with patients the risks of prostate cancer, the potential benefits and harms of screening, and involving the patients in the decision.[78]

However, because PSA screening is widespread in the United States, following the recommendations of major scientific and medical organizations to use shared decision-making is legally perilous in some U.S. states.[79] In 2003, a Virginia jury found a family practice residency program guilty of malpractice and liable for $1 million for following national guidelines and using shared decision-making, thereby allowing a patient (subsequently found to have a high PSA and incurable advanced prostate cancer) to decline a screening PSA test, instead of routinely ordering without discussion PSA tests in all men ≥ 50 years of age as four local physicians testified was their practice, and was accepted by the jury as the local standard of care.[80]

An estimated 20 million PSA tests are done per year in North America and possibly 20 million more outside of North America.[81]

  • In 2000, 34.1% of all U.S. men age ≥ 50 had a screening PSA test within the past year and 56.8% reported ever having a PSA test.[78]
  • In 2000, 33.6% of all U.S. men age 50–64 and 51.3% of men age ≥ 65 had a PSA test within the past year.[82]
  • In 2005, 33.5% of all U.S. men age 50–64 had a PSA test in the past year.
  • In 2000–2001, 34.1% of all Canadian men age ≥ 50 had a screening PSA test within the past year and 47.5% reported ever having a screening PSA test.[84]
  • Canadian men in Ontario were most likely to have had a PSA test within the past year and men in Alberta were least likely to have had a PSA test with the past year or ever.[85]

Digital rectal examination

Digital rectal examination (DRE) is a procedure where the examiner inserts a gloved, lubricated finger into the rectum to check the size, shape, and texture of the prostate. Areas that are irregular, hard, or lumpy need further evaluation, since they may contain cancer. Although the DRE evaluates only the back of the prostate, 85% of prostate cancers arise in this part of the prostate. Prostate cancer that can be felt on DRE is, in general, more advanced.[86] The use of DRE has never been shown to prevent prostate cancer deaths when used as the only screening test.[87]

Prostate specific antigen

The PSA test measures the blood level of prostate-specific antigen, an enzyme produced by the prostate. To be specific, PSA is a serine protease similar to kallikrein. Its normal function is to liquify gelatinous semen after ejaculation, allowing spermatozoa to more easily navigate through the uterine cervix.

PSA testing is controversial. Since the test was introduced PSA screening in the U.S. more than than 1 million additional men there have being diagnosed and treated for prostate cancer but it has been estimated that the vast majority (more than 95%) of these men receive no benefit from their positive diagnosis. Even if one makes the most optimistic assumption about the benefit of screening (i.e. that the entire decline in prostate cancer mortality observed since the introduction of PSA testing is due to introduction of the test) less than 5% (or one in twenty) of those getting a positive diganosis received any benefit at all from it. [88]

The risk of prostate cancer increases with increasing PSA levels.[89] 4 ng/mL was chosen arbitrarily as a decision level for biopsies in the clinical trial upon which the FDA in 1994 based adding prostate cancer detection in men age 50 and over as an approved indication for the first commercially available PSA test.[90] 4 ng/mL was used as the biopsy decision level in the PLCO trial, 3 ng/mL was used in the ERSPC and ProtecT trials, and 2.5 ng/mL is used in the 2007 NCCN guideline.

PSA levels can change for many reasons other than cancer. Two common causes of high PSA levels are enlargement of the prostate (benign prostatic hypertrophy (BPH)) and infection in the prostate (prostatitis). It can also be raised for 24 hours after ejaculation and several days after catheterization. PSA levels are lowered in men that use medications used to treat BPH or baldness. These medications, finasteride (marketed as Proscar or Propecia) and dutasteride (marketed as Avodart), may decrease the PSA levels by 50% or more.

Several other ways of evaluating the PSA have been developed to avoid the shortcomings of simple PSA screening. The use of age-specific reference ranges improves the sensitivity and specificity of the test. The rate of rise of the PSA over time, called the PSA velocity, has been used to evaluate men with PSA levels between 4 and 10 ng/ml, but it has not proven to be an effective screening test.[91] Comparing the PSA level with the size of the prostate, as measured by ultrasound or magnetic resonance imaging, has also been studied. This comparison, called PSA density, is both costly and has not proven to be an effective screening test.[92] PSA in the blood may either be free or bound to other proteins. Measuring the amount of PSA which is free or bound may provide additional screening information, but questions regarding the usefulness of these measurements limit their widespread use.[93][94]

Management

Treatment for prostate cancer may involve active surveillance, surgery, radiation therapy including brachytherapy (prostate brachytherapy) and external beam radiation therapy, High-intensity focused ultrasound (HIFU), chemotherapy, cryosurgery, hormonal therapy, or some combination. Which option is best depends on the stage of the disease, the Gleason score, and the PSA level. Other important factors are the man's age, his general health, and his feelings about potential treatments and their possible side-effects. Because all treatments can have significant side-effects, such as erectile dysfunction and urinary incontinence, treatment discussions often focus on balancing the goals of therapy with the risks of lifestyle alterations.

The selection of treatment options may be a complex decision involving many factors. For example, radical prostatectomy after primary radiation failure is a very technically challenging surgery and may not be an option.[95] This may enter into the treatment decision.

If the cancer has spread beyond the prostate, treatment options significantly change, so most doctors that treat prostate cancer use a variety of nomograms to predict the probability of spread. Treatment by watchful waiting/active surveillance, HIFU, external beam radiation therapy, brachytherapy, cryosurgery, and surgery are, in general, offered to men whose cancer remains within the prostate. Hormonal therapy and chemotherapy are often reserved for disease that has spread beyond the prostate. However, there are exceptions: radiation therapy may be used for some advanced tumors, and hormonal therapy is used for some early stage tumors. Cryotherapy (the process of freezing the tumor), hormonal therapy, and chemotherapy may also be offered if initial treatment fails and the cancer progresses.[96]

Prognosis

Prostate cancer rates are higher and prognosis poorer in developed countries than the rest of the world. Many of the risk factors for prostate cancer are more prevalent in the developed world, including longer life expectancy and diets high in red meat and reduced-fat dairy products to which vitamin A palmitate has been added.[97] (People that consume larger amounts of meat and dairy also tend to consume fewer portions of fruits and vegetables. It is not currently clear whether both of these factors, or just one of them, contribute to the occurrence of prostate cancer.[98]) Also, where there is more access to screening programs, there is a higher detection rate. Prostate cancer is the ninth-most-common cancer in the world, but is the number-one non-skin cancer in United States men. Prostate cancer affected eighteen percent of American men and caused death in three percent in 2005.[99] In Japan, death from prostate cancer was one-fifth to one-half the rates in the United States and Europe in the 1990s.[100] In India in the 1990s, half of the people with prostate cancer confined to the prostate died within ten years.[101] African-American men have 50–60 times more prostate cancer and prostate cancer deaths than men in Shanghai, China.[102] In Nigeria, two percent of men develop prostate cancer and 64% of them are dead after two years.[103]

In patients that undergo treatment, the most important clinical prognostic indicators of disease outcome are stage, pre-therapy PSA level and Gleason score. In general, the higher the grade and the stage the poorer the prognosis. Nomograms can be used to calculate the estimated risk of the individual patient. The predictions are based on the experience of large groups of patients suffering from cancers at various stages.[104]

In 1941, Charles Huggins reported that androgen ablation therapy causes regression of primary and metastatic androgen-dependent prostate cancer.[105] Androgen ablation therapy causes remission in 80-90% of patients undergoing therapy, resulting in a median progression-free survival of 12 to 33 months. After remission, an androgen-independent phenotype typically emerges, wherein the median overall survival is 23–37 months from the time of initiation of androgen ablation therapy.[106] The actual mechanism contributes to the progression of prostate cancer is not clear and may vary between individual patient. A few possible mechanisms have been proposed.[107] Androgen at a concentration of 10-fold higher than the physiological concentration has also been shown to cause growth suppression and reversion of androgen-independent prostate cancer xenografts or androgen-independent prostate tumors derived in vivo model to an androgen-stimulated phenotype in athymic mice.[108][109] These observation suggest the possibility to use androgen to treat the development of relapsed androgen-independent prostate tumors in patients. Oral infusion of green tea polyphenols, a potential alternative therapy for prostate cancer by natural compounds, has been shown to inhibit the development, progression, and metastasis as well in autochthonous transgenic adenocarcinoma of the mouse prostate (TRAMP) model, which spontaneously develops prostate cancer.[110]

Many prostate cancers are not destined to be lethal, and most men will ultimately die from causes other than of the disease. Decisions about treatment type and timing may, therefore, be informed by an estimation of the risk that the tumor will ultimately recur after treatment and/or progress to metastases and mortality. Several tools are available to help predict outcomes such as pathologic stage and recurrence after surgery or radiation therapy. Most combine stage, grade, and PSA level, and some also add the number or percent of biopsy cores positive, age, and/or other information.

The D’Amico classification stratifies men to low, intermediate, or high risk based on stage, grade, and PSA. It is used widely in clinical practice and research settings. The major downside to the 3-level system is that it does not account for multiple adverse parameters (e.g., high Gleason score and high PSA) in stratifying patients.

The Partin tables predict pathologic outcomes (margin status, extraprostatic extension, and seminal vesicle invasion) based on the same 3 variables, and are published as lookup tables.

The Kattan nomograms predict recurrence after surgery and/or radiation therapy, based on data available either at time of diagnosis or after surgery. The nomograms can be calculated using paper graphs, or using software available on a website or for handheld computers. The Kattan score represents the likelihood of remaining free of disease at a given time interval following treatment.

The UCSF Cancer of the Prostate Risk Assessment (CAPRA) score predicts both pathologic status and recurrence after surgery. It offers comparable accuracy as the Kattan preoperative nomogram, and can be calculated without paper tables or a calculator. Points are assigned based on PSA, Grade, stage, age, and percent of cores positive; the sum yields a 0–10 score, with every 2 points representing roughly a doubling of risk of recurrence. The CAPRA score was derived from community-based data in the CaPSURE database. It has been validated among over 10,000 prostatectomy patients, including patients from CaPSURE[111]; the SEARCH registry, representing data from several Veterans Administration and active military medical centers[112]; a multi-institutional cohort in Germany[113]; and the prostatectomy cohort at Johns Hopkins University.[114]

Epidemiology

Rates of prostate cancer vary widely across the world. Although the rates vary widely between countries, it is least common in South and East Asia, more common in Europe, and most common in the United States.[1] According to the American Cancer Society, prostate cancer is least common among Asian men and most common among black men, with figures for white men inbetween.[115][116] However, these high rates may be affected by increasing rates of detection.[117]

Prostate cancer develops most frequently in men over fifty. This cancer can occur only in men, as the prostate is absent in the female reproductive tract. It is the most common type of cancer in men in the United States with 186,000 new cases in 2008 and 28,600 deaths.[118] It is the second leading cause of cancer death in men after lung cancer. In the United Kingdom it is also the second most common cause of cancer death after lung cancer, where around 35,000 cases are diagnosed every year and of which around 10,000 die of it. However, many men that develop prostate cancer never have symptoms, undergo no therapy, and eventually die of other causes. That is because malignant neoplasms of the prostate are, in most cases, slow-growing, and because most of those affected are over 60. Hence they often die of causes unrelated to the prostate cancer, such as heart/circulatory disease, pneumonia, other unconnected cancers, or old age. Many factors, including genetics and diet, have been implicated in the development of prostate cancer. The Prostate Cancer Prevention Trial found that finasteride reduces the incidence of prostate cancer rate by 30%. There had been a controversy about this also increasing the risk of more aggressive cancers, but more recent research showed this was not the case.[42][119]

Potential mechanisms of disease progression

The insulin-like growth factor signaling axis is thought to play a key role in the progression of prostate carcinoma. It consists of two ligands (IGF-1 and IGF-2), two receptors (IGF-IR and IGF-IIR) and six related high-affinity IGF-binding proteins (IGFBP 1-6).[120] Altered expression of IGF axis members has been implicated in the development of many different types of cancers, including prostate.[121][122]

History

Although the prostate was first described by Venetian anatomist Niccolò Massa in 1536, and illustrated by Flemish anatomist Andreas Vesalius in 1538, prostate cancer was not identified until 1853.[123] Prostate cancer was initially considered a rare disease, probably because of shorter life expectancies and poorer detection methods in the 19th century. The first treatments of prostate cancer were surgeries to relieve urinary obstruction.[124] Removal of the entire gland (radical perineal prostatectomy) was first performed in 1904 by Hugh H. Young at Johns Hopkins Hospital.[125] Surgical removal of the testes (orchiectomy) to treat prostate cancer was first performed in the 1890s, but with limited success. Transurethral resection of the prostate (TURP) replaced radical prostatectomy for symptomatic relief of obstruction in the middle of the 20th century because it could better preserve penile erectile function. Radical retropubic prostatectomy was developed in 1983 by Patrick Walsh.[126] This surgical approach allowed for removal of the prostate and lymph nodes with maintenance of penile function.

In 1941, Charles B. Huggins published studies in which he used estrogen to oppose testosterone production in men with metastatic prostate cancer. This discovery of "chemical castration" won Huggins the 1966 Nobel Prize in Physiology or Medicine.[127] The role of the hormone GnRH in reproduction was determined by Andrzej W. Schally and Roger Guillemin, who both won the 1977 Nobel Prize in Physiology or Medicine for this work.

Receptor agonists, such as leuprolide and goserelin, were subsequently developed and used to treat prostate cancer.[128][129]

Radiation therapy for prostate cancer was first developed in the early 20th century and initially consisted of intraprostatic radium implants. External beam radiation became more popular as stronger radiation sources became available in the middle of the 20th century. Brachytherapy with implanted seeds was first described in 1983.[130] Systemic chemotherapy for prostate cancer was first studied in the 1970s. The initial regimen of cyclophosphamide and 5-fluorouracil was quickly joined by multiple regimens using a host of other systemic chemotherapy drugs.[131]

Jonathan Simons and his laboratories at Johns Hopkins and Emory made original contributions in the molecular biology of cytokines in human prostate cancer metastasis, and in the molecular pharmacology and genetic therapy of metastatic prostate cancer.

Prostate cancer models

Scientists have established a few prostate cancer cell lines to investigate the mechanism involved in the progression of prostate cancer. LNCaP, PC-3 (PC3), and DU-145 (DU145) are commonly used prostate cancer cell lines. The LNCaP cancer cell line was established from a human lymph node metastatic lesion of prostatic adenocarcinoma. PC-3 and DU-145 cells were established from human prostatic adenocarcinoma metastatic to bone and to brain, respectively. LNCaP cells express androgen receptor (AR); however, PC-3 and DU-145 cells express very little or no AR. AR, an androgen-activated transcription factor, belongs to the steroid nuclear receptor family. Development of the prostate is dependent on androgen signaling mediated through AR, and AR is also important during the development of prostate cancer. The proliferation of LNCaP cells is androgen-dependent but the proliferation of PC-3 and DU-145 cells is androgen-insensitive. Elevation of AR expression is often observed in advanced prostate tumors in patients.[132][133] Some androgen-independent LNCaP sublines have been developed from the ATCC androgen-dependent LNCaP cells after androgen deprivation for study of prostate cancer progression. These androgen-independent LNCaP cells have elevated AR expression and express prostate specific antigen upon androgen treatment. The paradox is that androgens inhibit the proliferation of these androgen-independent prostate cancer cells.[134][135][136]

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