Document 44yKzekqXKX5E3OYgYLxX7mJx

4 CANCER PREVENTION: UPDATE FOR PHYSICIANS Series Editors/Guy R. Newell, MD; IV. Bryant Boutwell, MPH, Department of Cancer Prevention Potential for Cancer Prevention * Guy R. Newell, MD; W, Bryant Boutwell, MPH Cancer prevention as a distinct, definable entity has come of age. some of the reasons for which have been enumerated by Cole.' The bottom line is that clinicians, scientists, admin istrators, legislators, and the public have come to the realiza tion that cancer prevention is both the most humane and the most economical way of controlling cancer. Cancer prevention can be defined as the identification of the causes of cancer in man. and their being rendered inef fective by whatever means. It also includes the detection and removal of early cancer before clinical disease is mani fested.1 Identification of the causes of cancer is usually done by laboratory investigations in animals, with subsequent ex trapolation to man, or by epidemiologic investigations in hu mans. Rendering causes of cancer ineffective may be accom plished by a variety of methods including removal of the cause from man's environment, neutralization, inactivation, and enhancement of the host-defense mechanisms. A brief statement about the known causes of cancer and their implications for cancer prevention is in order. Cigarette smoking remains undoubtedly the single, leading health hazard known to society. It easily accounts for 85% to 90% of all lung cancer, 40% of all cancers in males, and 25% of all cancers in females. On the basis of current smoking habits among women, lung cancer will surpass female breast cancer as the leading cause of cancer deaths among women by the mid-1980s--a startling fact in itself. Superimposed on this is the fact that teen-age girls are taking up the smoking habit at an alarming rate, which will only add to the female lung cancer problem in the future. Radiation is a known carcinogen. Because we receive ten times more radiation from natural background (at sea level) than we do from a single chest x-ray, constant exposure to small amounts of radiation throughout life seems inevitable. We know of no known or proposed way of avoiding, protect ing against, or preventing this carcinogenic exposure. One can avoid exposure to excessive medical or diagnostic x-ray. and for the most part, the radiation community monitors such exposure constantly. They have determined acceptable levels of exposure to x-rays based on careful and conservative riskbenefit considerations. Viruses, in all probability, contribute to the cause of Burkitt's lymphoma and liver cancer in Africa, to cervical can cer. and to nasopharyngeal cancer in southeastern Asia. Practical application of this knowledge for cancer prevention in the forseeable future is not at hand. Chemicals hold an interesting place in today's society. Some attribute much of cancer occurrence in man to chemi cals in the environment. It is generally held that a substance found to be carcinogenic for any animal must be presumed to be carcinogenic for man and therefore should be removed from contact with man. This is certainly a prudent approach, although obviously not always a practical one. Most chemi- *Presented at the Son Francisco Regional Cancer Foundation. Dec 3, 1980. San Francisco. California. cals have not been found to be carcinogenic for man. a though the vast majority have not been tested in animal bir assay systems. Most chemicals are not carcinogenic in thei native state. After entering the body as a procarcinoge: through inhalation, ingestion, or absorption, they must be ar tivated to a proximate carcinogen. Following this, they ma be detoxified and excreted harmlessly, or if they remain act; vated. they may go through a series of steps, resulting in a; ultimate carcinogen producing clinical carcinoma. The mor that is known about every step along this process, the mor; opportunity exists for blocking the process by various differ ent methods. Research into this area of chemical carcino genesis offers great future opportunity for the prevention c chemically induced cancers. Lifestyle practiced by individuals is becoming more im portant in allowing one to minimize his or her risk fo1 developing cancer. A prudent lifestyle for minimizing cancer risks includes cessation of all tobacco use; moderation o alcohol consumption; adequate protection in the workplace avoidance of carcinogenic drugs, hormones, and x-rays maintenance of ideal body weight by a suitable balance c caloric intake and exercise; and following a "prudent" diet. Diet and nutrition as a part of lifestyle deserves specio consideration. Diet refers to all those substances one ingests in the course of eating and drinking (natural contaminants additives, preservatives, colorings, etc). Nutrition refers tr those food elements that one needs to maintain body viabiliu (proteins, fats, carbohydrates, vitamins, and minerals). The many possible ways in which diet and nutrition may ad either to increase the risk of cancer, or equally important, to protect against cancer is beyond the scope of this paper; rsviews of the subject are available.1' Suffice it to say that most investigators today believe that pursuit of the role of diet and nutrition in the etiology and prevention of cancer is one o' the, if not the most, promising avenue for cancer prevention for the future. What may be done by individuals now to pre vent cancer is based on possible benefit and no known risk.'' This essentially consists of a standard diet that is higher in fi ber content and lower in total fat. Our own estimate of preventable cancers, modified from National Cancer Institute data, is given in Table 1. If these large numbers of cancer are preventable today, then why are they not being prevented? Should this be considered a fad ure? If so. where does the blame lie? Before attempting to answer these poignant questions, one should make a distinction between two important concepts-- "etiology" and "prevention." Etiology is a noun that means "knowing the cause of a disease." It is a scientific endeavor using investigative techniques, conducted by researchers, re sulting in truth, knowledge, or fact. Prevention comes from a verb, "to prevent," implying action. It is a public health en deavor, requiring education, motivation, legislation, and/or regulation, conducted by a variety of health and nonhealth professionals, which seeks to effect a change based on knowi 78 ng CANCER BULLETIN, VOL 33, NO 1, 19S1 Ucc 096859 Table 1. Estimated Preventable Cancers* Cancer Associated with Site Incidence Preventable Cigarette smoking Lung k larynx 90.000 plus alcohol Head k neck, esophagus 13.500 .ndustrial exposure Bladder 9,000 Oiel-related Breast 30.000 Colon 30,000 dux- related Cervix 7,500 nrJight Melanoma k othar skin 5,000 otal 185,000 Modified from Nalional Cancer Institute data. 80,000 8.500 5.000 10,000 10,000 7,500 1,500 122,500 ,lge of etiology. Change must occur at the individual or socital level. The process from etiology to prevention is compliated and difficult, at best. So. who is to blame for our current lack of cancer revention? Take cigarettes as an example: (1) Scientists say e have proved that cigarette smoking causes lung cancer, 'ur job is done; the rest is up to someone else. (2) Health lucators say it is impossible to get certain groups of men nd women to quit smoking, or now even to prevent teen-age :rls from beginning to smoke: therefore, the fault lies with nokers themselves. (3) Smokers say that wa will die of imething anyway, It is our right to choose to die from lung incer, emphysema, or cardiovascular disease if we want to. -.'sides, it must not be as bad as they say because governlent, who tends to overregulate everything else allows tobac> to be grown and to continue to be sold on the open market. :) Tobacco farmers say growing tobacco is the very livelijod for their families and the community, and how can it be denied them? (5) Public health officials who have no available legal sanctions take strong personal public stands against cigarette smoking, at times to their own personal detriment; other parts of the executive branch continue to subsidize the tobacco growers. (6) Legislators (politicians) say "you scratch my back and I'll scratch yours." Some 15 states grow tobacco, with the result being 30 senators of 100 who together form an obviously very strong coalition. (7) Industry says to proceed with more marketing, more advertising, more sales, and more profits. Results of the recent trend toward a less-hazardous cigarette remain to be evaluated. So, where does the blame lie? Individually, no one is to blame, but collectively, all are partially to blame. In the forseeable future, preventive action will continue to be a complex and sensitive balance of scienfi/ic knowledge that is often inadequate or imprecise, societal expectation that is often unrealistic, and political reality that is almost always pragmatic,1 References 1. Cole P; Some epidemiological aspects of cancer prevention, in Cancer in Ontario. Report of the Ontario Cancer Treatment and Re search Foundation. 1979, 2. Newell GR: Overview of cancer prevention. Cancer Bull 32:128129, 1980. 3. Berg (W: Diet in persons at high risk of cancer: An approach lo cancer etiology and control, in Fraumeni |F [r (ed): Persons at High Risk of Cancer: An Approach to Cancer Etiology and Control. New York, Academic Press, Inc, 1975, pp 201-224. 4. Hayes JR. Campbell TC; Nutrition as a modifier of chemical car cinogenesis, in Slaga T] (ed): Corcinogenesis: A Comprehensive Sur vey. New York, Raven Press. 1980, vol S. pp 207-241. 5. Ellison NM. Newell GR: Relationship between diet and cancer: A brief review for the practicing physician. Cancer Bull 32:157-160, 1980. 8. Bremmer SH. DeFelice RL: Dietary advice in regard to risk for colon and breast cancer. Prevent Med 9:544-549, 1980. CUMCAL CASE REEORTS/LT M. I). ANDERSON HOSPITAL Series Editor/Fred G. Conrad, MD. Vice President for Patient Care CISCA Chemotherapy for Bladder Cancer Christopher ]. Logothetis, MD, Section of General Medicine and Clinical Oncology Bladder cancer remains a major cause of morbidity and ortahty. with 10.300 bladder cancer deeths expected in '80.1 Experimental and clinical studies indicate that tuxan. Adriamycin, and cis-platinum (CISCA) are active .linst this tumor.11 Single agents or combinations of agents -vo achieved response rates from 404* to 604* but have iueved no complete remissions.1' This case dearly monstrates that, despite the metastatic stage of bladder ncer, aggressive CISCA chemotherapy combined with !vie infusions of cis-platinum are capable of achieving a mplete remission with prolonged palliation of symptoms. CASE 1. A 39-year-old white man was initially evaluated UT M. D. Anderson Hospital in December 1978. His history as normal, except for peptic ulcer disease. Six weeks prior this evaluation, he experienced frequency of urination, dy ne. and lower abdominal pain. Initial studies revealed evi dence of a lower abdominal and pelvic mass with bilateral hydronephrosis. Subsequent cystoscopy and biopsy revealed a poorly differentiated carcinoma. The patient was referred to UT M. D. Anderson Hospital for treatment. On examination, the patient was found lo be asthenic. He had prominent abdominal distention and a mass filling the lower abdomen. Rectal examination revealed a large mass constricting the rectum and involving the rectal mucosa and the prostate. The mess wes firmly fixed and nontender. Prominent large bowel distention was thought to be secon dary to incomplete bowel obstruction from the invading tumor. Neurologic and cardiopulmonary examinations were unremarkable; no lymphadenopathy wes evident; and the liver and spleen were not palpable. Laboratory studies on admission were hemoglobin. 9.5 mg/ 100 ml; platelets, 344,000; WBC count, 9,600/cu mm, with THE CANCER EULLETIN, VOL 33, NO 2. 1981 79 > UCC 096860