Winning the war on cancer.

Cancer is one of today's most-feared diseases, but you can do a lot to lower your risk.

Cancer is probably the most dreaded of all diseases; nearly everyone has close friends or relatives who have fallen victim to it. Cancer is now the leading cause of death for women and the second leading

Cancer will probably never be completely preventable. Yet it has been calculated that about two-thirds of all human cancers could be prevented.

In this article, I will compile and rank the major preventable cancer risk factors - i.e., those that are not inherited. While hereditary cancers carry a high risk if they run in your family, they are very rare otherwise. By focusing on preventable cancer risk factors, we can direct our personal choices and public policies toward achieving the maximum possible reduction in cancer mortality.

The top 25 preventable cancer risks in the United States are listed in the table at right.

Preventable Causes of Cancers

Of the top 25 completely preventable causes of cancer in the United States, about 84% are lifestyle-related. Those few that are not clearly lifestyle-related (such as hepatitis B virus infection, DDT exposure, and secondhand smoke) nevertheless can have a significant component of lifestyle choice involved. For example, hepatitis B virus (HBV) infection is more prevalent among homosexual men who engage in anal sex, high-level DDT exposure is usually occupational and can be minimized through careful application of the pesticide, and secondhand smoke is often avoidable.

At least 48% of the top 25 preventable causes of cancer are related to diet. This shows that the current emphasis on dietary prevention of cancer is not a misplaced effort, since diet is more easily changed than certain other lifestyle risk factors, such as tobacco use or obesity.

At least 28% of the top 25 preventable causes of cancer are specifically related to an inadequate intake of fruits and vegetables. This would seem to be a relatively easy dietary change to make, since modern farming and shipping practices make fresh fruits and vegetables available year-round to virtually everyone in the United States. Many cookbooks provide recipes that make vegetables more palatable, so all that may be required is the impetus to try these recipes. It is hoped that our analysis of cancer risk factors will provide such impetus.

One-fifth of the top 25 preventable causes of cancer are arguably stress-related, since stress can cause an increased intake of tobacco, alcohol, and total calories, and since many people respond to stress by becoming [TABULAR DATA OMITTED] obese. Dealing productively with stress can therefore play a critical role in maintaining a healthy lifestyle and minimizing the risk of cancer. Perhaps the most effective way to deal with stress is to establish a regular routine of exercise.

Other preventable risks are exposure to carcinogenic chemicals, such as tobacco smoke, hair dye, and DDT; HBV, for which a vaccine exists; and of course tobacco, which is known to cause at least 85% of all lung cancers and up to 30% of all other cancers.

Actual Causes of Death

A recent study examined the actual causes of death in the United States, with the specific goal of identifying the major nongenetic factors that contribute to death. Of the 2.1 million people who died in 1990, death certificates show that more than half a million people died of cancer, and that cancer was the second leading cause of death overall, after heart disease.

But medical terms (e.g., cancer), used to describe the physical condition at death, do not reveal the actual root causes of death. In order to get at the root causes of death in the United States, a large number of separate studies were analyzed in a sort of meta-analysis. The actual (nongenetic) causes of death identified in this meta-analysis were, in descending order of importance:

1. Tobacco. 2. Diet and activity patterns. 3. Alcohol. 4. Microbial agents. 5. Toxic agents. 6. Firearms. 7. Sexual behavior. 8. Motor vehicles. 9. Illicit use of drugs.

Together, these causes accounted for about half of all deaths in the United States in 1990.

Tobacco was the major root cause of death identified in the United States, taking 400,000 lives in 1990. Tobacco is responsible for about 19% of all deaths, 30% of all cancer deaths, 30% of all chronic lung disease deaths, 24% of all pneumonia and influenza deaths, 21% of all cardiovascular deaths, and a substantial fraction of deaths from cerebrovascular disease and diabetes. Without doubt, smoking is the most damaging carcinogen to which humans are regularly exposed.

Diet and activity patterns were the next most important root cause of death identified, taking 300,000 American lives in 1990. Dietary factors are responsible for deaths from cardiovascular disease, cancer, and diabetes, while physical inactivity is responsible for deaths from heart disease and cancer. Together, these factors account for at least 20% of all cancer deaths, 30% of all diabetes deaths, and 22% of all cardiovascular deaths.

Alcohol was the third most important root cause of death identified, taking 100,000 lives. An estimated 18 million people in the United States suffer from alcohol dependence, and 76 million are affected by alcohol abuse at some time during their lives. Alcohol abuse is responsible for at least 3% of all cancer deaths, 60% of all cirrhosis deaths, 40% of all motor vehicle fatalities, and 16% of all other injuries.

More than 20 times as many people died from cancer in 1990 as died from AIDS. Despite the public attention given to HIV/AIDS, various other viruses were far more important as a cause of death in the United States in 1990. Viruses caused about six times as many deaths from cancer as from AIDS in 1990, and the death toll from virally induced cancer is rising at a rate comparable to the death toll from AIDS in the United States. Thus, cancer must remain a major focus of the medical research enterprise.

Summary: Ten Things You Can Do To Lessen Your Risk of Cancer

1. Stop smoking. No rationale is possible for this devastating habit. Stop those you love from smoking or hound them senseless. Don't allow anyone to smoke in your house or your office, and make it as difficult as possible for smokers to abuse themselves. Smokeless tobacco is really no better than smoked tobacco - it just causes cancers that are somewhat less uniformly fatal than lung cancer.

2. Learn your familial risk factors and be especially vigilant about those cancers that seem to run in your family. Ask your older relatives for as full a description as possible of the cause of death of your deceased relatives, then specifically avoid the risk factors for these cancers.

3. Increase your consumption of fresh fruits and vegetables. A broad variety of each is best, with special emphasis on whatever is freshest in your produce department or store.

4. Decrease your consumption of red meat. This does not mean become a vegetarian, but rather place greater dietary emphasis on white meats, such as chicken and fish. An appropriate dietary modification might be as simple as having red meat fewer than four times per week, or having chicken or fish at least three times per week. Vegetarian dishes or dishes rich in complex carbohydrates (e.g., pasta) can also be substituted for red meat.

5. Exercise at least three times per week, for at least 20 minutes each time. This will help to maintain your weight at an appropriate level as well as conferring other benefits.

6. Get vaccinated against hepatitis B virus if at all possible and avoid other viral exposures. This may mean using a condom, minimizing the number of different sexual partners, or avoiding intercourse with someone you suspect to be infected with human papilloma virus.

7. Practice moderation in all things. Overuse or abuse of alcohol, prescription drugs, and fast foods takes a very high toll in the modern world, as does overexposure to sunlight.

8. Make a yearly visit to a physician if you are over 40 years old, and make biannual visits if you are over 30. This will certainly help to diagnose and treat current problems, but may also alert you to newly discovered cancer risk factors. In addition, there are several widely available cancer screening tests that should be used on the advice of your physician, including mammography, Pap test, fecal occult blood test, and prostate-specific antigen screening.

9. Avoid unnecessary exposure to the hormones used in estrogen-replacement therapy (ERT). Long-term ERT use by perimenopausal women is associated with an increased risk of breast cancer, especially if estrogen is combined with progestin. However, the benefits of ERT may outweigh the risks, since breast cancer risk may drop rapidly after discontinuation of the therapy.

10. Learn the 10 warning signs of cancer: (1) Swelling, thickening, or lump in any soft tissue, but especially the breasts. (2) Persistent or unexplained coughing or hoarseness. (3) A sore that does not heal or a mole that abruptly changes in size or color. (4) Unexplained fatigue. (5) Abrupt weight loss or loss of appetite. (6) Changes in bowel habits, including pain or bleeding on defecation, narrow stools, or constipation. (7) Changes in urinary function, particularly bleeding or difficulty in discharge. (8) Changes in menstrual function, especially unexpected or excessive bleeding. (9) Difficulty in swallowing or a feeling of bloat or fullness. (10) Pallor or abnormal bleeding.

Conclusion

Much of what we know about cancer prevention is common sense. Everyone should eat a balanced diet and practice moderation in all things. It is fair to say that cancer is a disease of abuse or disuse, and moderation may be key to avoiding both extremes.

Whenever possible, people should learn more about their personal risk factors. If there is a family history of cancer, especially if cancer has affected a particular organ in a large number of family members, special care should be taken to avoid known risk factors for that cancer. It would also be wise to be screened for that cancer whenever possible. In the absence of specific screening tests for a particular cancer, regular visits to a family physician can substantially reduce cancer risk. However, there is no substitute for common sense, moderation, and personal knowledge of cancer risk factors.

RELATED ARTICLE: Genetic Screening for Cancer

Cancer screening is the use of medical tests to examine people with no symptoms of cancer in order to determine if these people are in the early stages of developing disease. Current screening tests include the Pap smear, mammography, prostate-specific antigen test, fecal occult blood test, and colonoscopy. These tests are an important weapon in the war on cancer. According to the American Cancer Society, 100,000 people could have been saved in 1992 if there had been full implementation of current tests.

The ideal cancer screening test is reliable, inexpensive, easy to use, accurate, and gives adequate warning, so that the cancer can be successfully treated. It is fair to say that such a test does not yet exist. However, in the future, it may become possible to develop new tests based on an understanding of the genetic basis of cancer.

Genetic screening would be analogous to taking a genetic "fingerprint" of individuals to determine if they have mutations of tumor-suppressor genes. Genetic screening might be able to determine which cancer each person is most likely to get, to identify a cancer-prone person years before developing the disease, and to help a person avoid specific risk factors for cancer.

- R. Grant Steen

About the Author

R. Grant Steen is on the faculty of St. Jude Children's Research Hospital, where he studies brain tumor biology, and has conducted cancer research at Johns Hopkins Medical School. His address is Department of Diagnostic Imaging, St. Jude Children's Research Hospital, 332 North Lauderdale Street, Memphis, Tennessee 38105. Telephone 901/495-2014.

This article is adapted from his book Changing the Odds: Cancer Prevention through Personal Choice and Public Policy ([C] 1995 by R. Grant Steen. 388 pages. $35), used by arrangement with Facts On File, Inc., 11 Penn Plaza, New York, New York 10001. To order, call 800/322-8755.