The 10 commandments of cancer prevention

About one of every three Americans will develop some form of malignancy during his or her lifetime. This year alone, about 1,437,000 new cases will be diagnosed, and more than 565,000 people will die of the disease. Cancer is the second leading cause of death in America, and as deaths from heart disease decline, it's poised to assume the dubious distinction of becoming our leading killer.

Despite these grim statistics, doctors have made great progress in understanding the biology of cancer cells, and they have already been able to improve the diagnosis and treatment of cancer. But instead of just waiting for new breakthroughs, you can do a lot to protect yourself right now.

Get regular check-ups, including the screening tests that can help detect cancer before it causes any symptoms. For men between 15 and 35, that means a periodic doctor's testicular exam along with regular self-exams. All men older than 50 should have regular screening for colon cancer, and they should make an informed decision about testing for prostate cancer. Men with risk factors should begin both processes even earlier, and every man should routinely inspect himself for signs of melanomas and other skin cancers.

Screening tests can help detect malignancies in their earliest stages, but you should always be alert for symptoms of the disease. The American Cancer Society developed this simple reminder years ago:

• C: Change in bowel or bladder habits

• A: A sore that does not heal

• U: Unusual bleeding or discharge

• T: Thickening or lump in the breast or elsewhere

• I: Indigestion or difficulty in swallowing

• O: Obvious change in a wart or mole

• N: Nagging cough or hoarseness

It's a rough guide at best. The vast majority of such symptoms are caused by nonmalignant disorders, and cancers can produce symptoms that don't show up on the list, such as unexplained weight loss or fatigue. But it is a useful reminder to listen to your body and report sounds of distress to your doctor.

Early diagnosis is important, but can you go one better? Can you reduce your risk of getting cancer in the first place? It sounds too good to be true, but it's not. Scientists at the Harvard School of Public Health estimate that up to 75% of American cancer deaths can be prevented; the table below summarizes their research on the causes of cancer in the United States. The American Cancer Society is only slightly less optimistic about prevention, estimating that about 60% of America's cancer deaths can be avoided. And a 2005 study argues that over 2.4 million of the world's 7 million annual cancer deaths can be blamed on nine potentially correctable risk factors.

You don't have to be an international scientist to understand how you can try to protect yourself and your family. The 10 commandments of cancer prevention are:

1. Avoid tobacco in all its forms, including exposure to secondhand smoke.

2. Eat properly. Reduce your consumption of saturated fat and red meat, which appears to increase the risk of colon and prostate cancers. Limit your intake of charbroiled foods (especially meat), and avoid deep-fried foods. Increase your consumption of fruits, vegetables, and whole grains. Although other reports are mixed, two large 2003 studies found that high-fiber diets may reduce the risk of colon cancer. And don't forget to eat fish two to three times a week; you'll get protection from heart disease, and you may reduce your risk of prostate cancer.

3. Exercise regularly. Physical activity has been linked to a reduced risk of colon cancer, and it may even help prevent prostate cancer. Exercise also appears to reduce a woman's risk of breast and possibly reproductive cancers. Exercise will help protect you even if you don't lose weight.

4. Stay lean. Obesity increases the risk of many forms of cancer. Calories count; if you need to slim down, take in fewer calories and burn more with exercise.

5. If you choose to drink, limit yourself to one to two drinks a day. Excess alcohol increases the risk of cancers of the mouth, larynx (voice box), esophagus (food pipe), liver, and colon; it also increases a woman's risk of breast cancer. Smoking further increases the risk of many alcohol-induced malignancies.

6. Avoid unnecessary exposure to radiation. Get medical imaging studies only when you need them. Check your home for residential radon, which increases the risk of lung cancer. Protect yourself from ultraviolet radiation in sunlight, which increases the risk of melanomas and other skin cancers. But don't worry about electromagnetic radiation from high-voltage power lines or radiofrequency radiation from microwaves and cell phones. They do not cause cancer.

7. Avoid exposure to industrial and environmental toxins such as asbestos fibers, benzene, aromatic amines, and polychlorinated biphenyls (PCBs).

8. Avoid infections that contribute to cancer, including hepatitis viruses, HIV, and the human papillomavirus. Many are transmitted sexually or through contaminated needles.

9. Consider taking low-dose aspirin. Men who take aspirin or other nonsteroidal anti-inflammatory drugs appear to have a lower risk of colon cancer and possibly prostate cancer. It's an unproven benefit, and aspirin can produce gastric bleeding and other side effects, even in low doses. On the plus side, though, low-dose aspirin does protect men from heart attacks and the most common type of stroke; men at the highest risk reap the greatest benefits.

10. Get enough vitamin D. Many experts now recommend 800 to 1,000 IU a day, a goal that's nearly impossible to attain without taking a supplement. Although protection is far from proven, evidence suggests that vitamin D may help reduce the risk of prostate cancer, colon cancer, and other malignancies. But don't count on other supplements. Careful studies show that selenium, vitamins C and E, beta carotene, folic acid, and multivitamins are not protective, and that some may do more harm than good.

These lifestyle changes will yield another cancer-preventing benefit: if you stay healthy, you won't need cancer treatments (chemotherapy, radiotherapy, drugs that suppress the immune system) that have the ironic side effect of increasing the risk of additional cancers.

As always, prevention is the best medicine.