Understanding Cancer

A complex mix of factors related to environment, lifestyle, and heredity plays a role in the causation of cancer. For example, 80 percent of all cancers are related to the use of tobacco products, to what we eat and drink, and to our exposure to radiation, asbestos, and some of the other cancer-causing agents. There's not much you can do about your genes, but several other key risk factors are under your control. If you identify them and make the necessary changes in your lifestyle early enough, you can substantially decrease your chances of developing a malignancy. Here are some of the risk factors you can do something about:

• In the United States, tobacco is responsible for 85 to 90 percent of all lung cancers, and for one-third of all deaths related to other cancers (mouth, larynx, esophagus, stomach, pancreas, bladder, kidney, cervix, leukemia, and possibly colon). The magnitude of the risk depends on the number and kind of cigarettes you've smoked and for how long. A pack-a-day smoker is ten times more vulnerable than a nonsmoker. It's never too late to quit. After you do, your cancer risk declines gradually each year.
• Chronic alcohol abuse can cause cancer of the liver, as well as of the mouth, throat, esophagus, and larynx, especially in combination with tobacco. It may also raise the risk of breast cancer. You should limit yourself to the equivalent of two drinks a day.
• Diet: People who do not eat fruits and vegetables have roughly twice the incidence of most types of cancer—lung, larynx, oral cavity, esophagus, stomach, colon and rectum, bladder, pancreas, cervix, and ovary—than those with the highest intake. The National Cancer Institute and the National Research Council recommend eating two servings of fruit and three portions of vegetables a day.
• Some supplements seem to protect against certain cancers. For instance, colon polyps and cancer do not recur as often in persons who regularly take multivitamins, calcium supplements, and vitamin E. And in a recent study conducted in England, a daily dose of 50 milligrams of vitamin E reduced the incidence of prostate cancer. However, you're usually better off with the natural sources from which these supplements are extracted, rather than getting them from a bottle. A diet rich in fruits and vegetables is protective against cancer, presumably because of the beta-carotene content. Yet in a now-famous Finnish study, beta-carotene supplements appeared to increase the risk of lung cancer (as well as coronary artery disease and total mortality). Researchers enlisted thousands of heavy smokers especially vulnerable to cancer. The subjects were divided into two groups—one was given placebos, and the other, beta-carotene. After a few years, the latter, surprisingly, were found to have a 17 percent higher incidence of lung cancer!
• A high-fat diet is associated with cancer of the breast, uterus, and prostate. The guilty foods are eggs, fatty meats, high-fat salad dressings and cooking oils, and dairy products such as whole milk, butter, and most cheeses.
• Significant overweight is linked to cancer of the prostate, pancreas, uterus, colon, ovary, and, in older women, the breast.

In summary, the ideal healthy diet is one that's varied, well balanced, and includes at least five servings of fruits and vegetables each day; lots of grain, breads, and cereals (to provide the necessary fiber); and is as low in fat as possible.

• Ultraviolet radiation from sun, sunlamps, and tanning booths damages the skin and can cause skin cancer. Stay out of the bright sun between 11:00 a.m. and 3:00 p.m. If you must be in the sun during those hours, wear protective clothing (a hat, long sleeves) and apply sunblock with a protection factor of at least 15 to exposed areas.
• Don't have X rays any more frequently than is absolutely necessary. It is not recommended for patients to have routine annual chest films unless they are smokers or have lung or heart disease. Some dentists are too enthusiastic about dental X rays. Make sure you really need them before acquiescing.
• Chronic infection and inflammation are responsible for about a third of the world's cancers. Liver cancer in particular, which is very common in Asia and Africa, is increasing in frequency in this country because of hepatitis B and C. The major villain is the hepatitis C virus, which is currently causing a worldwide epidemic. Both hepatitis B and C viruses are transmitted via infected blood (from transfusions, by sharing infected needles, and, in some 7 percent of cases, through sexual activity.) Unless you're had routine liver-function blood tests, you are not likely to suspect you're a carrier harboring hepatitis C. After many years, liver damage, including cirrhosis (scarring) and liver cancer, becomes evident. Unlike hepatitis A and B, there is as yet no vaccine against hepatitis C.

There are 170 million carriers of hepatitis C worldwide, 4 million of whom are in this country and have no idea they're at risk. By contrast, only 1 million persons are infected with AIDS in the United States.) The majority with this disease contracted it from blood transfusions they received before 1990, when routine screening of blood for the virus first began. If you were given blood for any reason before 1990 or have at any time shared a needle with anyone or had sex with a stranger, it is recommended that you have your blood checked for hepatitis C.

• Schistosomiasis, a parasitic disease widespread in Asia and Egypt and contracted from polluted water, can cause cancer of the colon and urinary bladder. Be careful where you swim when vacationing in those areas.
• The human papilloma virus, spread by sexual contact, is a major risk factor for cervical cancer.
• Some drugs used in the treatment of cancer, especially those that waken the immune system, can actually cause another malignancy, such as leukemia, lymphoma, and sarcoma.
• Air pollution, especially indoors (where the concentration of pollutants is highest and where we spend 90 percent of our time), can cause cancer. The most important carcinogenic air pollutant is radon, a naturally occurring radioactive gas generated by the decay of trace amounts of radium in the earth's crust. Radon is believed to contribute to as many as 15,000 lung cancers a year in the United States, mostly among smokers (there is a synergistic effect between radon and tobacco).
• Water pollution is not a great cancer risk. Chlorination of water, an extremely important and effective public-health measure that keeps teeth healthy, does produce some chlorinated by-products that can result in cancer in rodents, but nobody believes that this is an important cause of human cancer.
• Helicobacter pylori, the organism present in many peptic ulcers, is also associated with gastric cancer. A simple antibiotic regimen of one to two weeks eradicates H. pylori, eliminating the possibility of it giving you stomach cancer.

Cancer prevention means controlling as many of these risk factors as possible and having regular checkups for its early detection.

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