Dictionary:
on·col·o·gy (ŏn-kŏl'ə-jē, ŏng-)  |
The branch of medicine that deals with tumors, including study of their development, diagnosis, treatment, and prevention.
[Greek onkos, mass, tumor + –LOGY.]
oncological on'co·log'i·cal (-kə-lŏj'ĭ-kəl) or on'co·log'ic (-lŏj'ĭk) adj.| 5min Related Video: oncology |
| Sci-Tech Encyclopedia: Oncology |
The study of cancer. There are five major areas of oncology: etiology, prevention, biology, diagnosis, and treatment. As a clinical discipline, it draws upon a wide variety of medical specialties; as a research discipline, oncology also involves specialists in many areas of biology and in a variety of other scientific areas. Oncology has led to major progress in the understanding not only of cancer but also of normal biology.
Cancer defies simple definition. It is a disease that develops when the orderly relationship of cell division and cell differentiation becomes disordered. In cancer, dividing cells seem to lose the capacity to differentiate, and they acquire the ability to invade through basement membranes and spread (metastasize) to many areas of the body through the bloodstream or lymphatics. Cancer is usually clonal, that is, it develops initially in a single cell. That abnormal cell then produces progeny that may behave rather heterogeneously. Some progeny continue to divide, some develop the capacity to metastasize, and some develop resistance to therapeutic agents. This single cell and its progeny, if unchecked, typically lead to the death of the host. See also Cancer (medicine).
Causes of cancer
Cancer is generally thought to result from one or more permanent genetic changes in a cell. In some cells a single mutational event can lead to neoplastic transformation, but for most tumors it appears that carcinogenesis is a multistep process. Although some rare congenital conditions lead to cancer in infancy, the vast majority of human cancers arise as a result of the complex interplay between genetic and environmental factors. Without question, there are forms of cancer clearly related to particular environmental exposures; it is equally clear, however, that these factors act on a genetic substrate that may be either susceptible or resistant to the development of cancer.
The emergence of cancer appears to involve the accumulation of genetic damage in a target tissue. Such complex genetic changes specific to tissues appear to underlie the progression to cancer. Such multistep progression is quite complicated to study in experimental systems. Much work has focused on the identification, isolation, and characterization of oncogenes, which have the ability to transform normal cells into cancer cells. More than 50 bona fide or putative oncogenes have been characterized and mapped throughout the human genome. See also Human genetics; Oncogenes.
Environmental factors involved in the development of cancers can be chemical, physical, or biological carcinogenic agents. At least three stages occur in the natural history of cancer development from environmental factors. The first stage is initiation, which is a specific alteration in the deoxyribonucleic acid (DNA) of a target cell; environmental agents may act by inducing expression of oncogenes. The second phase, promotion, involves the reversible stimulation of expansion of the initiated cell or the reversible alteration of gene expression in that cell or its progeny. Because promotion is thought to be reversible, it is a target for prevention. The final phase of carcinogenesis is progression. It is characterized by the development of aneuploidy and clonal variation in the tumor; these in turn result in invasiveness and metastasis. See also Mutagens and carcinogens.
Cancer prevention
An obvious starting point for cancer prevention is avoidance of environmental agents that contribute to carcinogenesis.
The role of diet in cancer prevention is controversial. Epidemologic evidence suggests a particularly strong link between a high-fat, high-calorie, low-fiber diet and an increased risk of colon cancer. But a change to a low-fat, low-calorie, high-fiber diet may not alter the risk. The addition to the diet of carotenoids, selenium, vitamins A, D, and E, and some short-chain fatty acids may prevent cancers in high-risk populations, but there is no evidence that any dietary supplement will prevent cancer. See also Nutrition.
There are a variety of clinical settings in which surgery may prevent cancer. For example, surgical removal of the thyroid will prevent medullary carcinoma in individuals with certain types of multiple endocrine neoplasia, breast removal can be preventive in familial breast cancer, and removal of the ovaries can prevent cancer in familial ovarian cancer.
Cancer biology
The study of cancer biology picks up where cancer etiology leaves off, namely, at the point where the tumor has developed into a clonal cluster of autonomously proliferating cells. The pathological correlate of this stage of tumor development is carcinoma in situ; a condition in which no tissue destruction is evident, but atypical-appearing cancer cells are present at their site of origin. The transition from carcinoma in situ to locally invasive cancer is accompanied by dissolution of the basement membrane, penetration of tumor cells through the membrane and into the supportive tissues, and disruption of the supportive tissues. Expansion of the primary tumor in locally invasive cancer is always accompanied by the development of blood vessels. The tumor cells can also invade regional blood vessels and lymphatics and circulate throughout the body, attaching to endothelium in a distant organ site, inducing retraction of the endothelium, and becoming attached to the endothelial basement membrane. Once attached to the basement membrane, the tumor cells are covered over by the endothelial cells and effectively separated from the flow of blood. Local dissolution of the basement membrane then occurs, allowing the tumor to completely spread into the tissue and reestablish a blood flow in the breached vessel. As it grows, more blood vessel development nourishes the enlarging tumor.
During metastasis, tumor cells must overcome host defenses. They have various mechanisms to do so. For example, they produce new cell surface receptors to facilitate basement membrane and matrix binding; make new enzymes such as collagenases, serine proteases, metalloproteinases, cysteine proteinases, and endoglycosidases to facilitate their invasiveness; and secrete motility factors to enable them to move through the holes and pathways created by their enzymes. They avoid detection by the immune system through a variety of techniques. Unlike animal tumors, most human tumors are poorly immunogenic. Tumor cells often produce factors that are immunosuppressive. See also Cellular immunology; Tumor.
An unexplained feature of metastasis is the propensity of certain tumor types to spread to specific organs.
Tumor detection
There are two major strategies to detect tumors at the earliest possible stage in their history: responding to the seven warning signals of cancer and screening populations at high risk. The seven danger signals of cancer are (1) unusual bleeding or discharge, (2) a lump or thickening in the breast or elsewhere, (3) a sore that does not heal, (4) change in bowel or bladder habits, (5) persistent hoarseness or cough, (6) persistent indigestion or difficulty in swallowing, and (7) change in a wart or mole.
Diagnosis
The diagnosis of cancer depends on the careful examination of biopsy material. Cancers arising in tissues having ectodermal or endodermal origins are generally called carcinomas; those derived from glands are called adenocarcinomas. Cancers arising in tissues derived from mesoderm are called sarcomas; those of lymphohematopoietic origin are lymphomas and leukemias. The cardinal microscopic features of malignancy are anaplasia, invasion, and metastasis.
Once a diagnosis of cancer is made, it is critical to determine the extent to which the disease has spread. This is called staging. It is distinct from grading, which is an assessment of histologic atypia performed with a microscope. Staging entails performing a careful physical examination, various radiographic studies, and perhaps surgical procedures (biopsies, endoscopies) to examine those sites to which a particular tumor type is most likely to spread. For example, patients with breast cancer often undergo evaluation of the liver, brain, and bones to search for metastatic disease, whereas patients with lymphoma generally require assessment of lymph node groups, bone marrow, and liver. Often the results of such staging tests determine the nature and extent of therapy.
Treatment
There are four major approaches to cancer treatment: surgery, radiation therapy, chemotherapy, and biological therapy. These modalities are often used together with additive or synergistic effects. Surgery and radiation therapy are most effective in curing localized tumors and together result in the cure of about 40% of all newly diagnosed cases. Once the cancer has spread to regional nodes or distant sites, it is generally incurable with the use of local therapies alone. Systemic administration of a combination of chemotherapeutic agents may cure another 10–15% of all patients. See also Chemotherapy; Radiology.
Relieving the symptoms of cancer and alleviating the side effects of agents used to treat it is another important aspect of treatment. Many agents and interventions are available for these purposes. Pharmacologic agents can control nausea and vomiting. Various strategies are available to control pain, improve appetite, and combat insomnia and mood changes. Surgical procedures and radiological techniques can palliate many of the complications of cancer that formerly were incapacitating. Even when the hope for a cure has dwindled, the oncologist can relieve much suffering.
| Dental Dictionary: oncology |
The scientific study which focuses on tumors and malignancy; the science of cancer.
| Health Dictionary: oncology |
The branch of medicine devoted to the study, treatment, and cure of cancer.
| Wikipedia: Oncology |
Oncology is the branch of medicine dealing with tumors (cancer). A medical professional who practices oncology is an oncologist. The term originates from the Greek onkos (ονκος), meaning bulk, mass, or tumor, and the suffix -logy, meaning "study of".
Oncology is concerned with:
Contents |
The most important diagnostic tool remains the medical history: the character of the complaints and any specific symptoms (fatigue, weight loss, unexplained anemia, fever of unknown origin, paraneoplastic phenomena and other signs). Often a physical examination will reveal the location of a malignancy.
Diagnostic methods include:
Apart from in diagnosis, these modalities (especially imaging by CT scanning) are often used to determine operability, i.e. whether it is surgically possible to remove a tumor in its entirety.
Generally, a "tissue diagnosis" (from a biopsy) is considered essential for the proper identification of cancer. When this is not possible, "empirical therapy" (without an exact diagnosis) may be given, based on the available evidence (e.g. history, x-rays and scans.)
Occasionally, a metastatic lump or pathological lymph node is found (typically in the neck) for which a primary tumor cannot be found. This situation is referred to as "carcinoma of unknown primary", and again, treatment is empirical based on past experience of the most likely origin.
It depends completely on the nature of the tumor identified what kind of therapeutical intervention will be necessary. Certain disorders will require immediate admission and chemotherapy (such as ALL or AML), while others will be followed up with regular physical examination and blood tests. A detailed discussion of treatment options according to the type of cancer is at the National Cancer Institute website with sections on adult cancers, pediatric cancers, and supportive care. There is also a section on complementary and alternative methods of treatment.
Often, surgery is attempted to remove a tumor entirely. This is only feasible when there is some degree of certainty that the tumor can in fact be removed. When it is certain that parts will remain, curative surgery is often impossible, e.g. when there are metastases elsewhere, or when the tumor has invaded a structure that cannot be operated upon without risking the patient's life. Occasionally surgery can improve survival even if not all tumour tissue has been removed; the procedure is referred to as "debulking" (i.e. reducing the overall amount of tumour tissue). Surgery is also used for the palliative treatment of some of cancers, e.g. to relieve biliary obstruction, or to relieve the problems associated with some cerebral tumors. The risks of surgery must be weighed up against the benefits.
Chemotherapy and radiotherapy are used as a first-line radical therapy in a number of malignancies. They are also used for adjuvant therapy, i.e. when the macroscopic tumor has already been completely removed surgically but there is a reasonable statistical risk that it will recur. Chemotherapy and radiotherapy are commonly used for palliation, where disease is clearly incurable: in this situation the aim is to improve the quality of and prolong life.
Hormone manipulation is well established, particularly in the treatment of breast and prostate cancer.
There is currently a rapid expansion in the use of monoclonal antibody treatments, notably for lymphoma (Rituximab), and breast cancer (Trastuzumab).
Vaccine and other immunotherapies are the subject of intensive research.
The application of ultrasound in the form of HIFU to solid tumors is under investigation.
A large segment of the oncologist's workload is the following-up of cancer patients who have been successfully treated. For some cancers, early identification of recurrence, with prompt treatment, can lead to better survival and quality of life. It depends on the nature of the cancer whether the follow-up lasts a number of years or remains "life long". Some hospitals have cancer programs approved by the American College of Surgeons and must adhere to standards set forth by that organization. One of those standards requires annual followup of every patient entered into the Cancer Program's Registry for the remainder of the patient's life. This sort of long-term follow-up helps in analysis of long-term survival and recurrence of patients' cancers many years after initial successful treatment.
Approximately 50% of all cancer cases in the Western world can be cured with radical treatment. For pediatric patients, that number is much higher. A large number of cancer patients will die from the disease, and a significant proportion of patients with incurable cancer will die of other causes. There may be ongoing issues with symptom control associated with progressive cancer, and also with the treatment of the disease. These problems may include pain, nausea, anorexia, fatigue, immobility, and depression. Not all issues are strictly physical: personal dignity may be affected. Moral and spiritual issues are also important.
While many of these problems fall within the remit of the oncologist, palliative care has matured into a separate, closely allied specialty to address the problems associated with advanced disease. Palliative care is an essential part of the multidisciplinary cancer care team. Palliative care services may be less hospital-based than oncology, with nurses and doctors who are able to visit the patient at home.
There are a number of recurring ethical questions and dilemmas in oncological practice. These include:
These issues are closely related to the patients' personality, religion, culture, personal, and family life. The answers are rarely black and white. It requires a degree of sensitivity and very good communication on the part of the oncology team to address these problems properly.
There is a tremendous amount of research being conducted on all frontiers of oncology, ranging from cancer cell biology to chemotherapy treatment regimens and optimal palliative care and pain relief. This makes oncology a continuously changing field.
Therapeutic trials often involve patients from many different hospitals in a particular region. In the UK, patients are often enrolled in large studies coordinated by Cancer Research UK (CRUK)[1], Medical Research Council (MRC)[2], the European Organisation for Research and Treatment of Cancer (EORTC)[3] or the National Cancer Research Network (NCRN).[4]
Many cancer patients seek extra help from complementary and alternative therapies, which fall outside the scope of conventional medicine. Many complementary therapies do not have a firm scientific or evidential base.
Nonetheless, many aspects of the patients life that fall outside of the scope of conventional western medicine may be addressed very effectively by alternative means. Alternative means can help the patient and the patients family cope with the prospect of death, depression, anorexia, day to day emotions and functions such as sleeping and eating, and other palliative care.
Complementary therapies are diverse and multifaceted. They can range from free of charge to exorbitantly expensive, ineffective, to beneficial, to downright hazardous. As a general rule, complementary or alternative therapy is only as effective as one believes it to be.
There are several sub-specialties within oncology. Moreover, oncologists often develop an interest and expertise in the management of particular types of cancer.
Oncologists may be divided on the basis of the type of treatment provided.[5]
In the United Kingdom and several other countries, oncologists may be either clinical or medical oncologists. The main difference is that clinical oncologists deliver radiotherapy, while medical oncologists do not. (This difference does not apply in North America: the terms, clinical oncologist and medical oncologist are used interchangeably.)
In most countries it is now common that patients are treated by a multidisciplinary team. These teams will meet on regular basis and discus the patients under their care. These teams consist of the medical oncologist , a clinical oncologist or radiotherapist, a surgeon (sometimes there is a second reconstructive surgeon), a radiologist, a pathologist, an organ specific specialist such as a gynaecologist or dermatologist, and sometimes the general practitioner is also involved. These disease oriented teams are sometimes in conflict with the general organisation and operation in hospitals. Historically hospitals are organised in an organ or technique specific manner. Multidisciplinary teams operate over these borders and it is sometimes difficult to define who is in charge.
In veterinary medicine, veterinary oncology is the sub-specialty that deals with cancer diagnosis and treatment in animals.
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| Translations: Oncology |
Nederlands (Dutch)
oncologie, afdeling oncologie van ziekenhuis
Français (French)
n. - oncologie
Deutsch (German)
n. - Onkologie, Geschwulstlehre
Ελληνική (Greek)
n. - (ιατρ.) ογκολογία
Português (Portuguese)
n. - oncologia (f)
Español (Spanish)
n. - oncología
Svenska (Swedish)
n. - onkologi
中文（简体）(Chinese (Simplified))
肿瘤学
中文（繁體）(Chinese (Traditional))
n. - 腫瘤學
العربيه (Arabic)
(الاسم) علم الأورام
עברית (Hebrew)
n. - תורת הגידולים (בגוף), אונקולוגיה
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved. Read more |
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| Health Dictionary. The New Dictionary of Cultural Literacy, Third Edition Edited by E.D. Hirsch, Jr., Joseph F. Kett, and James Trefil. Copyright © 2002 by Houghton Mifflin Company. Published by Houghton Mifflin. All rights reserved. Read more |
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| Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more |
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| Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Oncology". Read more |
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