Key Terms:
Definition
Chronic lymphocytic leukemia (CLL) is a cancer of white blood cells. In CLL, mature white blood cells of certain types, called lymphocytes, function abnormally and cause disease.
Description
Chronic leukemia is a cancer that starts in the blood cells made in the bone marrow. The bone marrow is the spongy tissue found in the large bones of the body. The bone marrow makes precursor cells called "blasts" or "stem cells" that mature into different types of blood cells. Unlike acute leukemias, in which the process of maturation of the blast cells is interrupted, in chronic leukemias, most of the cells do mature and only a few remain as immature cells. However, even though the cells appear normal, they do not function as normal cells.
The different types of cells produced in the bone marrow are red blood cells (RBCs), which carry oxygen and other materials to all tissues of the body, and white blood cells (WBCs), which fight infection. Platelets play a part in the clotting of the blood. The white blood cells can be further subdivided into three main types: the granulocytes, monocytes, and the lymphocytes.
The granulocytes, as their name suggests, contain granules (particles). These granules contain special proteins (enzymes) and several other substances that can break down chemicals and destroy microorganisms such as bacteria. Monocytes are the second type of white blood cell. They also are important in defending the body against pathogens.
The lymphocytes form the third type of white blood cell. There are two main types of lymphocytes: T lymphocytes and B lymphocytes. They have different functions within the immune system. The B cells protect the body by making "antibodies." Antibodies are proteins that can attach to the surfaces of bacteria and viruses. The occurrence of this attachment sends signals to many other cell types to travel through the blood and destroy the antibody-coated organism. The T cell protects the body against viruses. When a virus enters a cell, it produces certain proteins that are projected onto the surface of the infected cell. T cells recognize these proteins and produce certain chemicals (cytokines) capable of destroying the virus-infected cells. In addition, T cells destroy some types of cancer cells.
Chronic leukemias develop very gradually. The abnormal lymphocytes multiply slowly, and in a poorly regulated manner. These lymphocytes live much longer than normal lymphocytes and, thus, their numbers build up in the body. In CLL, lymphocytes accumulate. The enlarged lymphocyte population congregates in the blood, bone marrow, lymph nodes, spleen, and liver. The two types of chronic leukemias can be easily distinguished under the microscope. Chronic lymphocytic leukemia (CLL) involves the T or B lymphocytes. B-cell abnormalities are more common than T-cell abnormalities. T cells are affected in only 5% of the patients.
Demographics
Ninety percent of CLL cases are seen in people who are 50 years or older, with the average age at diagnosis being 65. Rarely is CLL diagnosed in a patient who is less than 35 years of age. The incidence of the disease increases with age. It is almost never seen in children. According to the estimates of the American Cancer Society (ACS), approximately 8,100 new cases of CLL were diagnosed in 2000, 4,600 in men and 3,500 in women.
CLL affects both sexes. Among patients younger than 65, the disease is slightly more common in men. However, among patients older than 75 years of age, CLL appears almost equally in men and women. Within the United States, CLL affects African-Americans as frequently as it does Caucasians. However, CLL appears more frequently among Americans than among people living in Asia, Latin America, and Africa.
In the United States and Europe, CLL accounts for more than one-quarter of all diagnosed leukemias. Over the past 50 years, the rate at which CLL has been appearing has increased significantly. However, many doctors think that this increase is not necessarily due to the disease actually being more common than in the past, but instead due to the fact that the disease is now more likely to be diagnosed when it does appear. Fifty years ago, only one out of ten CLL patients was diagnosed during the early stages of the disease. Now, half of all CLL patients are diagnosed during this early stage.
Causes and Symptoms
The cause of CLL is unknown. It is certain, however, that CLL is linked to genetic abnormalities and environmental factors. For example, close family members of patients with CLL are twice as likely to seven times as likely to be diagnosed with CLL as people in the general population. For another example, exposure to certain chemicals used in farming and other agricultural occupations may increase the risk that a person will develop CLL. In contrast, CLL is not associated with exposure to radiation known to cause other cancers. As of 2001, doctors were unsure whether people who have had certain virus infections are more likely to develop CLL than are people in the general population. If there does turn out to be such an association, it would not be with all viruses but with two human retroviruses (HTLVI and HTLV-II) or with Epstein-Barr virus (EBV).
The symptoms of CLL are generally vague and non-specific. One out of five patients with CLL has no symptoms at all, and the disease is discovered only through a routine blood test. A patient may experience all or some of the following symptoms:
- chronic fatigue
- weakness
- a general feeling of malaise or of things being not quite right
- swollen lymph nodes
- an enlarged spleen, which could make the patient complain of abdominal fullness
- a general feeling of ill health
- fever
- frequent bacterial or viral infections.
- unusually severe response to insect bites
- night sweats
- weight loss not due to dieting or exercise
Diagnosis
There is no screening test for CLL. If the doctor has reason to suspect leukemia, he or she will conduct a very thorough physical examination to look for enlarged lymph nodes in the neck, underarm, and pelvic region. In addition, the doctor will look to see whether the liver and spleen are enlarged. Urine and blood tests may be ordered to check for microscopic amounts of blood in the urine and to obtain a complete differential blood count. This count will give the numbers and percentages of the different cells found in the blood. An abnormal blood test might suggest leukemia. Some authorities state that CLL may be diagnosed if the number of lymphocytes in the blood exceeds a certain level.
The doctor may perform a bone marrow aspiration and biopsy to confirm the diagnosis of leukemia. During the bone marrow biopsy, a cylindrical piece of bone and marrow is removed. The tissue is generally taken out of the hipbone. These samples are sent to the laboratory for examination. In many CLL patients, more than one-fourth of the bone marrow is made up of mature lymphocytes. In addition to diagnosis, bone marrow biopsy is also conducted during the treatment phase of the disease to see if the leukemia is responding to therapy.
Some CLL patients have a condition called hypogammaglobulinemia. Immunoglobulins are normal parts of the body's immune system, the system used to fight off infection. Patients with hypogammaglobulinemia have very low levels of all of the various types of immunoglobulins.
The doctor may also conduct immunophenotyping. This involves taking a sample of the blood and looking at what types of cells of the immune system are being affected by the CLL. Approximately 19 out of 20 CLL patients have the B-cell type of CLL. Far more rare is the T-cell type of CLL. In addition, the doctor may look for abnormalities in the chromosomes of the affected cells. Chromosomes are a unit of genetic material within cells. Patients exhibiting no chromosomal abnormalities have a better prognosis than those who do have such abnormalities. If the abnormalities become more complex over time, the patient's prognosis may worsen.
Standard imaging tests such as x rays, computed tomography scans (CT scans), and magnetic resonance imaging (MRI) may be used to check whether the leukemic cells have invaded other organs of the body, such as the bones, chest, kidneys, abdomen, or brain.
Clinical Staging, Treatments, and Prognosis
Staging
Usually one of two systems are used to stage CLL. One of these is the Binet system and the other the Rai system. According to the Rai system, patients at low risk have no enlargement of lymph nodes, spleen or liver. The occurrence of these marks entry into the intermediate stage, according to Rai. High risk patients have, in addition, anemia and a significant decrease in the number of blood platelets in their blood. Blood platelets help blood to clot. According to the Binet system, a patient's stage depends upon how much hemoglobin (part of red blood cells that carry oxygen) and how many platelets are in the blood, as well as how many other areas the disease has affected. According to both systems, patients at low risk usually survive more than ten years. Patients at intermediate risk usually survive about six years. Patients at high risk usually survive about 2 years. Other factors with important implications for prognosis include the pattern at which bone marrow is being affected by the CLL and the amount of time it takes for the number of lymphocytes to double.
Treatment
Because the long-term prognosis for many patients with CLL is excellent, many patients receive no treatment at all at first. Many patients go for years before developing aggressive disease that requires treatment. Treatment for early stage CLL should be started only when one of the following conditions appears:
- Symptoms of the disease are growing worse, for example, there is a greater degree of fever, weight loss, night sweats, and so forth.
- The spleen is enlarging or enlargement of the spleen has become painful.
- Disease of the lymph nodes has become more severe.
- The condition of the bone marrow has deteriorated and there is anemia and a marked reduction in the number of blood platelets.
- There is anemia or reduction in the number of blood platelets for reasons not specifically related to the condition of the bone marrow.
- The population of lymphocytes is rapidly growing.
- The patient is experiencing numerous infections caused by bacteria.
Therapy for CLL usually starts with chemotherapy. Depending on the stage of the disease, single or multiple drugs may be given. Drugs commonly prescribed include fludarabine, cladribine, chlorambucil and cyclophosphamide. Studies have also provided evidence that a combination of fludarabine and cyclophosphamide is effective. However, this combination has not yet been evaluated over periods of ten years or more. Another combination now being studied involves fludarabine and mitoxantrone (Novantrone). Yet another involves fludarabine and anthracyclines. Low-dose radiation therapy may be given to the whole body, or it may be used to alleviate the symptoms and discomfort due to an enlarged spleen and lymph nodes. The spleen may be removed in a procedure called a splenectomy.
Bone marrow transplantation (BMT) has produced some positive outcomes in patients with CLL, although it has not been the subject of sufficient systematic study to permit doctors to know how effective it is. In BMT, the patient's diseased bone marrow is replaced with healthy marrow. There are two ways of performing a bone marrow transplant. In an allogeneic bone marrow transplant, healthy marrow is taken from another person (donor) whose tissue is either the same or very closely resembles the patient's tissues. The donor may be a twin, a sibling, or a person who is not related at all. First, the patient's bone marrow is destroyed with very high doses of chemotherapy and radiation therapy. To replace the destroyed marrow, healthy marrow from the donor is given to the patient through a needle in the vein.
In the second type of bone marrow transplant, called an autologous bone marrow transplant, some of the patient's own marrow is taken out and treated with a combination of anticancer drugs to kill all the abnormal cells. This marrow is then frozen to save it. The marrow remaining in the patient's body is then destroyed with high-dose chemotherapy and radiation therapy. Following that, the patient's own frozen marrow is thawed and given back to the patient through a needle in the vein. The use of this mode of bone marrow transplant for the treatment of CLL is currently being investigated in clinical trials.
Allogeneic BMT has been successfully used with younger patients with CLL who have not responded positively to chemotherapy. Autologous BMT has produced some positive results in older CLL patients. However, BMT is generally not considered an option in treating most patients with CLL because they are too old to be considered good candidates for the procedure.
Other CLL therapies that are being investigated include monoclonal antibody-targeted therapy and interferons. Monoclonal antibodies (MoAbs) are laboratory-manufactured chemicals that closely resemble parts of the body's natural immune system. Studies of MoAbstargeted therapies have shown some positive results in CLL, although definitive studies have not been performed at the time of this writing in 2001. Interferon is a chemical normally made in the cells of the body. It helps protect the body against viruses and also seems to have some effect against certain cancers. The interferon used as medicine is a laboratory-manufactured copy of the interferon produced by the body. As of this writing in 2001, interferon therapy has produced some response in CLL patients. However, interferon therapy has not as yet been shown to be associated with prolongation of remission.
Radiation therapy is very effective for approximately one in three of those CLL patients for whom it is considered appropriate.
Because leukemia cells can spread to all the organs via the blood stream and the lymph vessels, surgery is not considered an option for treating leukemias.
Treatment of Cll and Its Complications
During therapy for CLL, complications frequently appear. Many patients develop infectious illnesses. Sometimes, two or more infectious diseases attack a patient at the same time. These infections should be treated with great care. Most people whose death has been directly attributed to CLL have actually died from bacterial infections. The patient should be involved in identifying symptoms of infection and reporting these to the doctor without delay. Doing so may save the patient's life.
Many patients develop anemia, which is treated with the drug prednisone. Patients who do not respond to prednisone therapy may have their spleen removed and may receive therapy with immunoglobulin, a component of the blood.
Treatment After Transformation of Cll
Between three and ten out of every hundred patients with CLL experiences transformation of the disease into large-cell lymphoma (LCL). When this happens it is called Richter's transformation. Its occurrence is often marked by fever, weight loss, and night sweats. Treatments for LCL are being studied, although outcomes have not been very good. Very infrequently, CLL may transform into another disease, called prolymphocytic leukemia. Attempts to develop adequate therapies for this disease are ongoing.
Prognosis
For many CLL patients, the prognosis is excellent. Using the Binet and Rai staging systems, patients at low risk usually survive more than ten years. Patients at intermediate risk usually survive about six years. Patients at high risk usually survive about two years. The average patient survives approximately nine years following diagnosis. Factors with important implications for prognosis that are not included in the Binet or Rai systems are the pattern at which bone marrow is being affected by the CLL and the amount of time it takes for the number of lymphocytes in the blood to double. It is uncertain whether BMT may prolong the lifespan of CLL patients. Many of the chemotherapy agents used to treat disease do effectively control the leukemia and its effects but, as yet, the more established chemotherapy agents have not been shown to increase the life span of patients.
Coping With Cancer Treatment
Since many CLL patients die from infection, it is essential that patient be very alert to the signs of infection. If patients perform this role and seek medical attention as soon as symptoms of infection appear, then treatment can be started early. This may save a life.
It is very difficult for some patients to be not only informed that they have leukemia but then to also be told that they do not need treatment. This may be very confusing, unless the patient realizes that treatment may be necessary at some future time and that starting therapies too soon may be counterproductive.
Because nutritional alteration, weight loss, and psychosocial problems may accompany CLL, it may be prudent for patients to consult with a registered dietitian.
Cancer patients need supportive care to help them come through the treatment period with physical and emotional strength in tact. Many patients experience feelings of depression, anxiety, and fatigue, and many experience nausea and vomiting during treatment. Studies have shown that these can be managed effectively if discussed with the attending physician.
Prevention
Although some cancers are related to known risk factors, such as smoking, in leukemias, there are no known risk factors. Therefore, at the present time, there is no way known to prevent the leukemias from developing. Everyone should undergo periodic medical checkups.
Resources
Books
Braunwald, Eugene, et al. Harrison's Principles of Internal Medicine. 15th ed. New York: McGraw-Hill, 2001.
Herfindal, Eric T., Dick R. Gourley. Textbook of Therapeutics: Drug and Disease Management. 7th ed. Philadelphia: Lippincott Williams & Wilkins, 2000.
Humes, H. David, et al. Kelley's Textbook of Internal Medicine. 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2000.
Pazdur, Richard, et al. Cancer Management: A Multidisciplinary Approach: Medical, Surgical, & Radiation Oncology. 4th ed. Melville, NY: PRR, 2000.
Periodicals
Mauro, F. R., et al. "Clinical characteristics and outcome of young chronic lymphocytic leukemia patients: A single institution study of 204 cases." Blood 1999; 94: 448-454.
Organizations
The American Cancer Society publishes useful texts, such as Adult Chronic Leukemia-Overview, Leukemia-Adult Chronic: Treatment, Leukemia-Adult Chronic: Detection and Symptoms, Leukemia: Adult Chronic FAQ [Frequently Asked Questions], and Leukemia-Adult Chronic: Prevention & Risk. Call 1-800-ACS-2345 or on the Internet at
The Leukemia & Lymphoma Society (Formerly Leukemia Society of America) publishes useful texts available through the Internet or by mail, including Chronic Lymphocytic Leukemia (CLL), Making Intelligent Choices About Therapy, Understanding Blood Counts, Patient Aid Program, Family Support Group, and Information Resource Center. Call 1-800-955-4572 or visit on the Internet at
The National Cancer Institute publishes useful texts available through the internet or by mail, and answers questions by telephone. Some titles include: What You Need to Know about Leukemia and PDQ-Treatment-Patients: Chronic Lymphocytic Leukemia. Call 1-800-4CANCER or visit on the Internet at
National Coalition for Cancer Survivorship. 1010 Wayne Avenue, 7th Floor, Silver Spring, MD 20910-5600. Telephone: (301) 650-9127 and (877) NCCS-YES [877-622-7937). Web site:
—Lata Cherath, Ph.D.; Bob Kirsch
