<text> GUIDELINES FOR THE EARLY DETECTION OF CANCER IN ASYMPTOMATIC PEOPLE --------------------------------------------------------------- (Type of Cancer; Test; For Whom and How Often). ---------------------------------------------------------------Colon and rectal. Sigmoidoscopy: visual examination of colon, rectum, and anus using an endoscope. Everyone over 50; every 3-5 years. Colon. Stool slide test: stool is collected and chemically treated to find presence of blood. Everyone over 50; annually. Rectal. Digital rectal examination: physician physically feels for any abnormalities in rectal area. Everyone over 40; annually. Cervical. Pap test: cells removed from vagina and cervix area are examined under a microscope for any irregularities. All women who are, or who have been sexually active, or have reached age 18; frequency at doctor's discretion after three normal annual tests. Uterine and cervical. Pelvic examination: physician physically examines pelvic area for any irregularities. All women who are, or who have been sexually active, or have reached age 18; frequency at doctor's discretion after three normal annual exams. Uterine. Endometrial tissue sample: tissue removed from the uterine lining is examined under a microscope for any irregularities. All women who are, or who have been sexually active, or have reached aged 18; frequency at doctor's discretion after three normal annual exams. Breast. Breast self-exam: personal examination of breasts to feel for lumps. All women 20 and over; monthly. Breast. Breast physical examination: physician feels for any abnormalities in breast area. All women 20-40--every 3 years; women over 40--annually. Breast. Mammography: X rays of breasts. Women 35-39--once; women 40-49--every 1 to 2 years; women over 40--annually. Thyroid, testicular, prostate, ovarian, lymph nodes, mouth, skin. Checkup and health counseling: complete physical exam and discussion about cancer-preventing measures. Everyone over 20--every 3 years; everyone over 40--annually. --------------------------------------------------------------- SOURCE: American Cancer Society. </text>
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<text>American Cancer Society, American Cancer Society's Complete Book of Cancer (1986); Anderson, Paul N., et al., eds., Advances in Cancer Control (1989); Bannaset, P., ed., Cancer Therapy (1989); Bolognesi, Dani, Human Retroviruses, Cancer and AIDS (1988); Bronson, Kenneth W., ed., Local Invasion and Spread of Cancer (1989); Critzer, James R., Jr., Cancer: Diagnosis and Treatment (annual); Hunter, Tony, "The Proteins of Oncogenes," Scientific American, August 1984; Laszlo, John, Understanding Cancer (1987); Levitt, Paul M., et al., The Cancer Reference Book: Direct and Clear Answers to Everyone's Questions, rev. ed. (1983); Patterson, James T., The Dread Disease (1987); Pitot, Henry C., Fundamentals of Oncology, 3d ed. (1985); Prescott, David M., and Flexer, Abraham S., Cancer: The Misguided Cell, 2d ed. (1986); Robertson, Miranda, "Clues to the Genetic Basis of Cancer," New Scientist, June 9, 1983; Roth, Jay S., All about Cancer (1985); Siegel, Mary-Ellen, The Cancer Patient's Handbook (1986).</text>
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card_9064.xml
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<text>Because cancer is the most feared disease in the society of developed nations, numerous psychological reactions and problems affect the cancer patient. The delay in seeking medical help for a health problem that the patient fears might be cancer is a tragic example, because in many instances delay may mean the difference between effecting a cure or not. This fear is sometimes so great that it results in a tendency toward suicide. Such extreme reactions are unwarranted, for in the 1980s the cure rate has been one in three cases, and the potential cure rate is one in two cases. Patients with cancer have various psychological reactions related to their sociocultural backgrounds, the site of the tumor, their knowledge of and experience with cancer, and their personal evaluation of the clinical situation and the medical care they receive. The psychological problems become more serious with recurrent tumors because of greater fear of the outcome or doubt on the part of the patient with regard to the physician's expertise; the patient's relations with relatives, friends, and business associates are also factors. Cancer is a frightening but not a desperate disease. Education, reassurance, love, and understanding, as well as competent psychiatric therapy where clearly indicated, are all necessary for the complete care of the cancer patient. </text>
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<text>Most developed countries have programs of cancer research. In the United States, the National Cancer Institute of the federal government and such private organizations as the American Cancer Society, the Damon Runyon-Walter Winchell Cancer Fund, and the Leukemia Society of America have focused on cancer research and education. Researchers at the World Health Organization and such programs as the International Agency for Research on Cancer cooperate worldwide on cancer studies and public education on cancer. Knowledge of the causes and control of cancer has increased dramatically in recent years. In 1983, for example, U.S. and British researchers determined that at least two genetic changes may be needed to transform cells into cancerous cells under laboratory conditions: one stage enables the cell to grow indefinitely; the other stage enables the cell to ignore signals from surrounding cells that would otherwise halt its growth. Also, because the means to identify most of the carcinogenic agents in the environment are now available, a major program of cancer prevention is within reach. Vaccination against the few known viruses causing human cancer is realistically possible. Educational campaigns encouraging the modification of life-styles in modern society are potentially a major area of applied cancer research. Therapy in the future may be directed toward the chemical induction of differentiation of cancer cells into stable, nondividing cell populations. Evidence from animal experiments that some malignant cells can develop into perfectly normal cells when placed in the early embryo suggests that the neoplastic transformation is not always irreversible. Also, the potential for combination chemotherapy in human cancer has not been completely exhausted. Trials of new drug combinations in the human patient will continue as long as this method offers the best hope for the cure of the greatest number of metastatic neoplasms.</text>
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<text>For most patients, rehabilitation is a continuous process after therapy. Most cancers are considered cured if the patient exhibits no recurrence within 5 years. Some tumors require 10 years or more without further clinical signs before a cure is considered definitive. Although many patients, especially those suffering from leukemia, may show a remission of all symptoms and signs of the disease following therapy, such remission may not be permanent even though it may last, in some cases, for several years. A relapse of the neoplastic disease after remission is usually more difficult to treat than the initial occurrence.</text>
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<text>The success of cancer treatment is usually measured by the number of surviving patients. Equally important, but more difficult to analyze, is the quality of life of such patients. Rehabilitation of the cancer patient after definitive therapy is critical for the patient's complete care. Restoration of function that had been altered by surgical, radiation, or drug treatment is most important wherever possible. When a permanent deformity or dysfunction results from therapy, rehabilitation must play a supportive role in returning the patient to self-supporting status. Finally, for those patients whose therapy has not been curative, palliative rehabilitation is important in order for the patient to maintain some degree of independence with a reasonable degree of comfort.</text>
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<text><span class="style1">ecently, therapies combining less radical forms of surgery with radiation, chemotherapy, and/or "preventive" therapy have been employed. Such therapy has been especially useful in the treatment of breast cancer, where the traditional radical </span><span class="style2"><a href="#" class="group">MASTECTOMY</a></span><span class="style1">, involving removal of the breast, lymph nodes, and parts of the arm and chest muscles is becoming less common. It is being replaced by relatively simple surgery involving removal of only the lump itself or the breast, followed by chemotherapy or the use of preventive drugs. An example of the latter is tamoxifen, an anti-estrogen that prevents the growth of cancer cells with little or no toxity to the host and remaining normal cells.</span></text>
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<id>28</id>
<text>MASTECTOMY</text>
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card_7792.xml
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<text>While drug therapy seeks to kill all the cancer cells in the host by a direct toxic action on the cancer cell, stimulation of the host's own immune defenses treatment with antibodies specific for the neoplasm, or direct stimulation of lymphocytes that are effective in destroying cancer cells have been used in immunotherapy for cancers in humans and animals. Although as yet this type of treatment has been successful in selected cases only, the increasing availability of specifically "engineered" antibodies and monoclonal antibodies, and the use of growth factors (lymphokines) to stimulate the activity and replication of tumor-specific killer lymphocytes, offer promise for such immunotherapy in the future.</text>
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<text><span class="style1">nce metastasis of most malignant neoplasms has occurred, surgical and, for the most part, radiation therapy is not curative. Just as for infectious diseases, systemic treatment is necessary if eradication of the disease from the patient is to be possible. Although complete cure is uncommon for many of these neoplasms, chemotherapy, or treatment by chemical agents, has been instrumental in increasing the useful lifetime of many patients, especially children afflicted with various forms of cancer. A dozen or more advanced cancers that respond to drugs include acute lymphocytic leukemia in children; </span><span class="style2"><a href="#" class="group">HODGKIN'S DISEASE</a></span><span class="style1">, a form of malignant lymphoma; Burkitt's lymphoma; Ewing's sarcoma of bone; and Wilms's tumor of the kidney. All these neoplasms have the characteristic of rapid growth. In general, responsiveness of a cancer to drug therapy is related to the growth fraction of the tumor, that is, the percentage of cells undergoing cell division at any one time. Rapidly growing cancers have large growth fractions; a greater proportion of the cell population, therefore, is susceptible to the cytocidal and cytostatic (literally, cell-stopping or growth inhibiting) effects of chemotherapeutic drugs. The search for and development of new drugs to treat cancer has been prolonged and tedious. The development of effective anticancer drugs involves such stages as selection of the compound to be studied, screening for its effectiveness in animal systems, a study of the pharmacology, or how the body handles the drug, and finally extensive trials in patients. Compounds that have been effective in the chemotherapy of human cancer include certain hormones, especially the steroid sex hormones and those from the adrenal cortex; antibiotics produced naturally by a variety of microorganisms; plant alkaloids, including vinblastine and vincristine, derived from the periwinkle flower; alkylating agents--chemicals that react directly with DNA; and antimetabolites, which resemble normal metabolites (metabolic compounds) in structure and compete with them for some metabolic function, thus preventing further utilization of normal metabolic pathways. Different drugs act by various mechanisms and affect cells in different ways at different times; furthermore, some of these agents act synergistically, producing even better effects when used in combination. For this reason, modern treatment of cancer by chemotherapy, for the most part, employs multiple drug therapies simultaneously. Combination chemotherapy, although complicated from the therapeutic standpoint, has been most successful in treating a variety of neoplasms, especially leukemia, Hodgkin's disease, testicular cancer, and ovarian carcinoma. An added advantage of the combination technique is the relatively slow rate at which the tumor becomes resistant to drug therapy; such resistance commonly occurs when single drugs are used to treat a specific cancer.</span></text>
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<id>28</id>
<text>HODGKIN'S DISEASE</text>
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card_7343.xml
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<text><span class="style1">n all screening techniques a positive result must be confirmed by accepted diagnostic criteria, the most commonly used being the microscopic recognition of cancer by the pathologist. To obtain a specimen for diagnosis, surgical intervention is usually required. The removal of a suspected neoplasm or a portion of it for diagnostic purposes is termed a </span><span class="style2"><a href="#" class="group">BIOPSY</a></span><span class="style1">. If a biopsy is positive for malignancy, definitive therapy can be instituted immediately. Surgical removal of cancer is the oldest and most classical method of treatment. Curative surgery is performed on a primary neoplastic lesion, either benign or malignant, when no evidence of metastases is present. If metastatic lesions are present, surgery may be performed to remove the primary tumor or even some metastatic tumors in order to reduce the total amount of cancerous tissue in the body. This type of surgery is preparative to other types of therapy or is performed to alleviate such specific abnormalities as blockage of blood circulation, obstruction of the bowel, or severe pain from invasion of nerve trunks. The success of </span><span class="style2"><a href="#" class="group">RADIATION THERAPY</a></span><span class="style1">, such as using gamma rays emitted by cobalt-60 or using X rays--depends on the source of the radiation as well as the susceptibility of the neoplasm to killing by radiation. Malignant lymphomas, leukemias, and most carcinomas are relatively sensitive to radiation, at least during the first such treatments. Sarcomas are classically more resistant to radiation therapy. A major problem with radiation therapy is delivering the radiation in the most efficient manner--so that the maximal tumor destruction occurs with minimal damage to healthy tissue.</span></text>
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<content>
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<id>28</id>
<text>BIOPSYRADIATION THERAPY</text>
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card_7103.xml
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<text><span class="style1">f the treatment of cancer is to be successful, in most cases the diagnosis must be made at an early stage in the natural history of the disease, preferably before progression of the neoplasm to metastatic growth has occurred. Although no known single test exists that can uniformly detect all early human cancers, a number of methods for early detection have been developed. Paramount among these is the use of diagnostic cytology, especially the </span><span class="style2"><a href="#" class="group">PAP TEST</a></span><span class="style1">, developed by a Greek physician, George N. Papanicolaou, more than 50 years ago for determining the presence of cancer of the uterine cervix. The death rate from cervical and endometrial cancer has decreased significantly since the institution of this routine screening procedure. Early diagnosis of bladder, breast, lung, stomach, and esophageal cancer by various cytological procedures is also possible. Cancer "markers"--biochemical factors easily determined by laboratory methods from samples of serum, urine, or other body material--have also been used. Some enzyme activities, such as acid phosphatase in prostate cancer, have also permitted early diagnosis. Radiographic screening methods (see </span><span class="style2"><a href="#" class="group">RADIOLOGY</a></span><span class="style1">) have included the chest </span><span class="style2"><a href="#" class="group">X RAY</a></span><span class="style1"> in the past and, more recently, </span><span class="style2"><a href="#" class="group">MAMMOGRAPHY</a></span><span class="style1"> of the breast women as a screen for early breast cancer. Tests for blood in the stool are rapidly becoming accepted for screening for early colon cancer.</span></text>
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<id>28</id>
<text>MAMMOGRAPHYPAP TESTRADIOLOGYX RAY</text>
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card_6704.xml
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<text>The prevention of cancer, as of any disease, depends on the knowledge available about its causes and natural history. The majority of human cancer, perhaps 80 or even 90 percent, is related to the environment, and thus identification and elimination or control of these environmental factors would seem to be the most logical approach to cancer prevention. Two widely used methods are used for discovering cancer-causing agents. The Ames test, which rapidly measures the ability of a test agent to cause mutations in bacteria, is more than 90 percent effective and is widely used to identify potential carcinogens, which then may be tested in animals. The identification of carcinogenic chemicals by animal testing is tedious and expensive, but it is the only way to be certain that a particular agent is a carcinogen. The prevention of human cancer associated with virus infections--especially those cancers associated with the Epstein-Barr and hepatitis-B viruses--by means of vaccination is theoretically possible but has not yet been developed on any significant scale. Sunlight is likely to be the greatest single cause of skin cancer, but because of the high rate of cure of skin cancer, serious preventive efforts have been made only relatively recently. Such efforts have been directed particularly toward treating malignant melanoma, a rare form of sunlight-induced skin cancer that is difficult to cure. Human cancer related to exposure to X rays, gamma rays, and other high-energy radiation is much less common, largely as a result of federal controls. Cancer-causing environmental factors are probably related more closely to the promotion stage of the natural history of cancer than to any other. Breast cancer in women, for instance, is clearly related to dietary fat intake, and lung cancer, the most common cancer in men, is caused by continued and prolonged exposure to cigarette smoke. Although cigarette smoke contains many initiating agents, the cessation of smoking results in a negligible risk of lung cancer after a year or so. The incidence of the disease is directly related to the continued exposure to cigarette smoke, because of the continued action of promoting agents known to exist in this substance. Cancer prevention can thus come about by such measures as the cessation of cigarette smoking and the reduction of dietary fat and calories.</text>
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<text>Once a tumor has resulted from initiation and promotion, it may progress from a benign to a malignant form or from a low-grade malignancy to a rapidly growing, highly malignant cancer. Progression of a neoplasm occurs when a cell that has one or more significant abnormalities in one or more chromosomes grows and multiplies excessively. It is in the stage of progression that the activation of c-oncogenes may be most readily demonstrated. In addition, it is in this stage that the elimination and/or inactivation of tumor suppressor genes can be demonstrated either by specific loss or alteration of chromosomes or segments of chromosomes or through the study of genetic polymorphisms by recombinant DNA technology. A major component of tumor progression is metastasis, by which cells originating in the primary neoplasm can spread in a number of ways: through the bloodstream or lymphatic system, by direct implantation, or by surgical intervention, thereby establishing secondary growths. These metastatic growths, virtually without exception, exhibit chromosomal abnormalities and usually lead to death of the host. Although millions of cells metastasize from a primary neoplasm, only a few--probably those with certain as yet undeciphered genetic capabilities--establish metastatic lesions in various sites of the body. Some neoplasms may "pause" and remain latent for years before continuing their progression to malignancy. Other neoplasms, even after they are well into the stage of progression and exhibit metastases, may stop growing, differentiate, and remain quiescent for the remaining life span of the host. An example of a neoplasm that may do this in humans is the neuroblastoma of the adrenal gland, a tumor that commonly arises during childhood.</text>
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<text>One of the general characteristics of the development of cancer is the extended period of time between the initial exposure to a carcinogen and the appearance of a neoplasm. This latency phenomenon, known as tumor induction time, occurs with virtually every type of carcinogen. Beginning in the late 1940s, a number of investigators defined the early stages in the development, or natural history, of cancer. In a classical experiment performed on the skin of mice, a single application of an agent induced no neoplasms, but when it was followed by several applications of a second agent, termed the promoter, neoplasms developed. Initiation by the first agent is irreversible and, once imprinted in a cell, may be followed by promotion months or even years later. Promoting agents themselves do not induce neoplasms, and unlike initiation, promotion is reversible: if the applications of the promoting agent are repeated at long, rather than short, intervals, no neoplasms result even though the total dose of the promoting agent in the two cases is the same. Furthermore, promotion of neoplasms may be modulated by such factors as diet, hormones, environmental agents, and cell aging. This two-stage process of initiation and promotion is a general phenomenon in the natural history of cancer development in many tissues. Some promoting agents exhibit tissue specificity, such as phenobarbital, which promotes only liver cancer, and saccharin, which appears to be specific for bladder neoplasia. In humans, alcoholic beverages, dietary fat, and many of the components in cigarette smoke are effective promoting agents.</text>
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<text><span class="style1">ancer may develop suddenly and result in rapid deterioration of the victim, or it may grow slowly for years. A person may be unaware of a developing cancer and receive treatment only in the late stages. The </span><span class="style2"><a href="#" class="group">AMERICAN CANCER SOCIETY</a></span><span class="style1"> has promoted over the years public awareness of the seven warning signals of cancer: (1) a change in bowel or bladder function; (2) a sore that does not heal; (3) unusual bleeding or discharge; (4) a thickening or lump in the breast or elsewhere; (5) indigestion or difficulty in swallowing; (6) an obvious change in a wart or a mole; and (7) a nagging cough or hoarseness. With one or more of these symptoms, a person is urged to see a physician immediately.</span></text>
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<id>28</id>
<text>AMERICAN CANCER SOCIETY</text>
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card_5857.xml
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<text><span class="style1">hile it is unclear why cancer develops in some individuals and not in others, heredity appears to play a role in certain cancers. For this reason, the family history--a record of diseases and the cause and age of death of family members--may be important in predicting and diagnosing cancer. Some hereditary cancers include familial polyposis of the colon, which comprises small benign tumors of the large intestine that invariably develop into colon cancer; retinoblastoma, which is a tumor of the retina occurring in children; and a type of breast cancer that arises before the age of 40. While these types of cancers exhibit a dominant mode of inheritance (see </span><span class="style2"><a href="#" class="group">HEREDITY</a></span><span class="style1">) at the cellular level, they are recessive, requiring the alteration of both copies of the affected gene in order for a cell to become malignant. This means that the affected gene acts to suppress the neoplastic phenotype, since those cells with at least one normal copy of the critical gene do not express neoplastic properties. In contrast, activation of c-oncogenes acts in a truly dominant manner at the cellular level to cause the neoplastic phenotype. Recessive disorders include xeroderma pigmentosum, a severely disfiguring skin disorder that results from abnormalities in the organism's ability to repair damage to DNA and is invariably associated with several different types of human cancer, including skin cancer. Ataxia telangiectasia is another recessive disorder, characterized by nervous-system disorders and abnormal dilation of small blood vessels; Hodgkin's disease, leukemia, and certain cancers of the brain are among the neoplasms associated with this disease. Other forms of cancers, such as chronic myelogenous leukemia, are associated with specific structural abnormalities in the chromosomes of the neoplastic cells. Certain chromosomal structural abnormalities characteristically seen in specific leukemias and other malignant neoplasms have been related to the activation of c-oncogenes in those neoplastic cells exhibiting such structural abnormalities.</span></text>
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<id>28</id>
<text>HEREDITY</text>
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<text><span class="style1">ltraviolet and high-energy radiation are also causative agents for human and animal cancer (see </span><span class="style2"><a href="#" class="group">RADIATION INJURY</a></span><span class="style1">). A correlation exists between exposure to the sun's ultraviolet rays and the occurrence of skin cancer in humans. Cancers caused by radiation include leukemia as well as cancer of the thyroid, breast, stomach, uterus, and bone. Thus such routine diagnostic tools as the X ray are used with care so that a person is not overexposed; physicians also caution people using sunlamps, which employ ultraviolet rays, against excessive exposure. Physically induced sarcomas can be produced when plastic or other films or disks are inserted under the skin, as demonstrated in experimental animals. After the implant has remained within the animal for nearly half its life, sarcomas usually develop around the implant. If the implant is pulverized or its structure markedly altered before insertion under the skin, no neoplasms develop. The implant's physical structure rather than the chemical composition, of the implant is, therefore, the cause of the cancer. A similar circumstance occurs with </span><span class="style2"><a href="#" class="group">ASBESTOS</a></span><span class="style1">, an inorganic crystal that irritates the mesothelial lining of the lungs, inducing mesotheliomas in people and animals. A definite crystalline structure of this inorganic compound is required for its carcinogenic properties, and destruction of this crystalline form results in no tumor formation.</span></text>
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<id>28</id>
<text>ASBESTOSRADIATION INJURY</text>
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card_5188.xml
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<text><span class="style1">arious forms of parasites have been associated with many animal and plant cancers, although the actual linking mechanisms remain unknown or unproved. For example, the blood flukes that cause </span><span class="style2"><a href="#" class="group">SCHISTOSOMIASIS</a></span><span class="style1"> frequently seem, further, to cause bladder cancer, a cancer particularly prevalent in Egypt. The most clearly established biological agents, however, are the oncogenic (cancer-causing) viruses that commonly induce the formation of neoplasms in lower animals. A very few of these viruses are now strongly linked with some human cancers, and at least one has definitely been proven to cause a form of leukemia. Among the viruses strongly linked with human cancers are a number of </span><span class="style2"><a href="#" class="group">PAPILLOMA</a></span><span class="style1"> viruses and a </span><span class="style2"><a href="#" class="group">HERPES</a></span><span class="style1"> virus, called the Epstein-Barr virus, that causes the disease known as infectious mononucleosis. This latter virus is also suspected of causing the malignancy called Burkitt's lymphoma, prevalent in Africa, and a cancer of the nose and throat that commonly occurs in China. Another human cancer related to a virus infection is a liver carcinoma that sometimes follows a </span><span class="style2"><a href="#" class="group">HEPATITIS-B</a></span><span class="style1"> infection. Another link established between a human cancer and a virus is that between T-cell leukemia and a form of </span><span class="style2"><a href="#" class="group">RETROVIRUS</a></span><span class="style1"> called HTLV-l; the cancer appears to be endemic in certain parts of Japan, the West Indies, and the southeastern United States. Oncogenic (cancer-causing) viruses can be divided into DNA and RNA viruses depending on their genome structure (see </span><span class="style2"><a href="#" class="group">VIRUS</a></span><span class="style1">). The DNA viruses mainly insert their genetic information directly into the cells of their hosts although the Epstein-Barr virus instead appears to exist in multiple copies as a nucleic material known as a </span><span class="style2"><a href="#" class="group">PLASMID</a></span><span class="style1"> in the host cell's nucleus, separate from the host DNA. The RNA viruses such as the HTLV-l virus, on the other hand, require first that their genetic information be transcribed into DNA by an enzyme, called reverse transcriptase, supplied by the virus. All forms of oncogenic viruses contain one or more genes that are essential for the transformation of the infected cell into a neoplastic cell. Such genes, termed </span><span class="style2"><a href="#" class="group">ONCOGENES</a></span><span class="style1">, are best characterized in the genomes of oncogenic RNA viruses. It is now apparent that such oncogenes have closely related counterparts in the normal cellular genome of the cells they infect. The viral form of the oncogene, however, has a different structure and appears to be activated and expressed abnormally by one mechanism or another, leading to neoplastic transformation of the cell. Some oncogenic viruses may activate the normal cellular counterparts of oncogenes, called c-oncogenes, by one of several mechanisms, thus causing the neoplastic transformation to occur. Possibly similar mechanisms may result from the action of chemicals or radiation, or both, resulting in the activation of c-oncogenes.</span></text>
<text><span class="style1">hemicals that cause cancer have a variety of molecular structures and include complex hydrocarbons, aromatic amines, and certain metals, drugs, hormones, and naturally occurring chemicals in molds and plants. Many nitrosamines--simple organic oxides of nitrogen--are carcinogenic and may be produced within the human body. Hydrocarbons and nitrosamines are components of cigarette smoke and may be the carcinogenic agents contributing to lung cancer in smokers. Certain aromatic amines, especially 2-naphthylamine, were originally used in the dye industry for dyeing cloth and other materials. After it became apparent that this chemical caused a high incidence of bladder cancer in workers (see </span><span class="style2"><a href="#" class="group">DISEASES, OCCUPATIONAL</a></span><span class="style1">), it was no longer used industrially. Another industrial chemical gas, </span><span class="style2"><a href="#" class="group">VINYL</a></span><span class="style1"> chloride, has been implicated as the causative agent of sarcoma of blood vessels in the livers of exposed workers. Several drugs, including certain alkylating agents used to treat cancer, are also carcinogenic; although these chemicals are used to break DNA strands of cancer cells, thereby killing the cells, this same property causes the agent to induce cancer in normal cells. High levels of estrogens--a group of female hormones--administered to women after menopause result in an increased incidence of cancer of the uterus. To counteract this problem, today menopausal women are given estrogen in combination with progesterone. Aflatoxin B, a complex molecule produced by strains of the mold </span><span class="style2"><a href="#" class="group">ASPERGILLUS</a></span><span class="style1">, causes various cancers, particularly liver cancer. Certain salts containing arsenic are probably causally related to cancer of the skin and liver. That such a variety of apparently unrelated chemical structures can induce cancer by a common mechanism was indicated by the work in the 1960s of James and Elizabeth Miller, who demonstrated that chemical carcinogens, in order to exert their carcinogenic effect, must first be metabolized to an active, or "ultimate," form capable of reacting directly with cellular macromolecules, especially DNA. This and other research has strongly suggested that the formation of a cancer from a normal cell results from a chemical or structural alteration in the DNA of that cell.</span></text>
<text>A cancer-causing agent--chemical, biological, or physical--is termed a carcinogen. Substances are labeled carcinogens if, when administered to a population of previously untreated organisms, they cause a statistically significant increase in the incidence of neoplasms compared with the incidence in subjects that are left untreated.</text>
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<text><span class="style1">ancer is the common term used, by lay people and professionals alike, to designate the most aggressive and usually fatal forms of a larger class of diseases known as neoplasms. A neoplasm is described as being relatively autonomous because it does not fully obey the biological mechanisms that govern the growth and metabolism of individual cells and the overall cell interactions of the living organism. Some neoplasms grow more rapidly than the tissues from which they arise; others grow at a normal pace but because of other factors eventually become recognizable as an abnormal growth and not normal tissue. The changes seen in a neoplasm are heritable in that these characteristics are passed on from each cell to its progeny, or daughter cells. Neoplasms occur only in multicellular organisms, not in such unicellular organisms as bacteria or protozoa. The principal classification of neoplasms as either benign or malignant relates to their behavior. Several relative differences distinguish these two classes. A benign neoplasm, for instance, is encapsulated, but malignant neoplasms are not. Malignancies grow more rapidly than benign forms and invade adjacent, normal tissue. Tissue of a benign tumor is structured in a manner similar to that of the tissue from which it derived; malignant tissue, however, has an abnormal and unstructured appearance. Most malignant tumors, in fact, exhibit abnormalities in the structure of their chromosome structure--that is, the structure of the DNA molecules that constitute the genetic material duplicated and passed on to subsequent generations of cells (see </span><span class="style2"><a href="#" class="group">GENETIC CODE</a></span><span class="style1">; </span><span class="style2"><a href="#" class="group">NUCLEIC ACIDS</a></span><span class="style1">). Most important, however, benign neoplasms do not metastasize--that is, begin to grow at sites other than the point of origin--whereas malignant tumors do (see </span><span class="style2"><a href="#" class="group">METASTASIS</a></span><span class="style1">). The term cancer always denotes a malignant neoplasm, whereas the term </span><span class="style2"><a href="#" class="group">TUMOR</a></span><span class="style1"> indicates a readily defined mass of tissue distinguishable from normal living tissue. Thus a scar, an abscess, and a healing bone callus are all tumors but are not neoplasms. Besides being classified according to their behavior, neoplasms can also be classified according to the tissue from which they arose and are usually designated by a tissue-type prefix. A general system of nomenclature has also arisen to distinguish benign and malignant neoplasms. The designation of a benign neoplasm usually is signified by the suffix -oma added to the appropriate tissue-type prefix. Malignant neoplasms are separated into two general classes. Cancers arising from such supportive tissues as muscle, bone, and fat are termed sarcomas. Cancers arising from such epithelial tissues as the skin and the lining of the mouth, stomach, bowel, or bladder are classified as carcinomas. Examples of benign neoplasms are a lipoma (from fat tissue) and an osteoma (from bone). Malignant counterparts of these neoplasms are a liposarcoma and an osteosarcoma. The term adenoma is used to indicate a benign neoplasm of glandular tissue, and corresponding malignancies are termed adenocarcinomas. Exceptions to this form of nomenclature include thymomas, which are either malignant or benign neoplasms of the thymus gland, and such descriptive terms as dermoid, a benign tumor of the ovary. The suffix -blastoma denotes a primitive, usually malignant, neoplasm. </span><span class="style2"><a href="#" class="group">LEUKEMIA</a></span><span class="style1">, literally meaning "white blood," is the term used to designate malignant neoplasms having a major portion of their cells circulating in the bloodstream. Most leukemias arise in the blood-forming tissues, such as the bone marrow, and in the lymphatic tissues of the body.</span></text>
<text><span class="style1">n modern society cancer is the disease most feared by the majority of people throughout the world, supplanting the "white death," or tuberculosis, of the last century; the "black death," or bubonic plague, of the Middle Ages; and the leprosy of biblical times. Cancer has been known and described throughout history, although its greater prevalence today is undoubtedly due to the conquest by medical science of most infectious diseases and to the increased life span of humans. The study of cancer is known as the field of </span><span class="style2"><a href="#" class="group">ONCOLOGY</a></span><span class="style1">. In the mid-1980s nearly 6 million new cancer cases and more than 4 million deaths from cancer were being reported world-wide each year. The most common fatal form was stomach cancer (prevalent in Asia), but lung cancer has risen rapidly, because of the spread of cigarette smoking in developing countries, to become the leading fatal cancer in the world today. Also on the increase is the third-greatest killer, breast cancer, particularly in China and Japan. The fourth on the list is colon or rectum cancer, a disease that mainly strikes the elderly. In the United States in the mid-1980s, more than one-fifth of all deaths were caused by cancer; only the cardiovascular diseases accounted for a higher percentage. In 1990 the American Cancer Society predicted that about 30 percent of Americans will eventually develop some form of the disease. In the United States skin cancer is the most prevalent cancer in both men and women. Lung cancer, however, causes the most deaths in both men and women. </span><span class="style2"><a href="#" class="group">LEUKEMIA</a></span><span class="style1">, or cancer of the blood, is the most common type seen in children. An increasing incidence of cancer has been clearly observable over the past few decades, due in part to improved cancer screening programs, to the increasing number of older persons in the population, and also to the large number of tobacco smokers--particularly among women (see </span><span class="style2"><a href="#" class="group">SMOKING</a></span><span class="style1">). Some researchers have estimated that if Americans stopped smoking cigarettes, lung-cancer deaths could virtually be eliminated within 20 years. The U.S. government and private organizations spent about $1.2 billion annually for cancer research in the early 1980s, and more than $20 billion annually on the care and treatment of cancer patients. Because of the marked improvement in the types of drugs available and in the methods by which drug therapy is given, the number of deaths among cancer patients under 30 years of age is decreasing, even though the number of deaths from cancer is increasing in the population as a whole.</span></text>
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<text>LEUKEMIAONCOLOGYSMOKING</text>
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<text>Cancer TYPES CAUSES Chemical Agents Biological Agents Physical Agents Inherited Cancer STAGES Initiation and Promotion Progression PREVENTION DIAGNOSIS AND TREATMENT Surgery and Radiation Chemotherapy Immunotherapy Recent Trends Rehabilitation Remission PRESENT AND FUTURE RESEARCH PATIENT PSYCHOLOGYBibliography TABLE</text>
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