Many of the factors that influence your chances of developing breast cancer--your age or inheritance of a breast cancer susceptibility gene--are beyond your control. Others present opportunities for change, and several large research studies are looking at possibilities for intervention--changing medication, diet, or behavior to prevent or delay onset of disease.

The Breast Cancer Prevention Trial is a randomized study of tamoxifen, a drug that has been widely used in the treatment of women with breast cancer. Because tamoxifen, when taken for 5 years, has been found to markedly reduce the occurrence of new cancers in the opposite breast of a woman who has already had breast cancer, it is now being tried as a prevention treatment in healthy women at increased risk for breast cancer either because they are age 60 or older, or because they are between the ages of 30 and 59 and have combinations of high-risk factors.

Nutrient chemoprevention is being tested in research studies in Italy, where women who have already been treated for breast cancer are taking 4-HPR, a synthetic form of vitamin A, in hopes of preventing cancer in the opposite breast. Other researchers are investigating the protective potential of several other vitamins, including C and E. Yet other scientists are checking out naturally occurring chemicals, called phytochemicals, found in common fruits, vegetables, and other edible plants, in hopes of finding cancer-fighting substances that can be extracted, purified, and added to our diets.

Diet itself is another target of prevention research. In the Women's Health Initiative, a project of the National Institutes of Health, 70,000 women over age 50 are enrolled in a series of clinical studies to measure the effectiveness of prevention strategies for coronary heart disease, cancer, and osteoporosis. Strategies under study include a low-fat diet (less than 20 percent of calories from fat) and calcium plus vitamin D supplements, along with hormone replacement therapy. Another large study evaluating a low-fat diet in high-risk women is under way in Canada.

A much more drastic approach to breast cancer prevention is surgery to remove both breasts. Such a procedure, known as prophylactic mastectomy, is sometimes chosen by women with a very high risk for breast cancer--for instance, carrying a genetic mutation in BRCA1 or BRCA2, having a mother and one or more sisters with premenopausal breast cancer, plus a diagnosis of atypical hyperplasia and a history of several breast biopsies.

Unless a woman finds that anxiety is undermining the quality of her life, she is usually counseled not to choose this physically and psychologically draining surgery. The vast majority of breasts removed prophylactically show no signs of cancer. Moreover, since even a total mastectomy can leave a small amount of breast tissue behind, it cannot guarantee the woman will remain cancer-free. The preferred approach for most high-risk women is careful watching with clinical breast exams and mammography once or twice a year.

If you are considering a prophylactic mastectomy, with or without subsequent breast reconstruction, you will want to get a second opinion, preferably from a breast specialist. There is seldom reason to rush your decision. Many doctors advise a woman to give herself several months to weigh the options.

If your risk for breast cancer is high, you might also consider talking with a genetic counselor about gene testing for breast cancer susceptibility. (See Gene Testing, page 18.)

Whether your risk of breast cancer is average or higher, there are some steps you can take:

• Follow early detection practices. Ask your doctor when you should begin mammograms at regular intervals. Get regular breast exams by a doctor or nurse.
  
• Consult your doctor about your personal situation and carefully weigh any potential risks against the benefits in making decisions about hormone-containing drugs. Stay informed as new research findings become available.
  
• Exercise and eat a balanced diet that provides a good variety of nutrients and plenty of fiber. Limit dietary fat and alcohol. These are good health measures that make sense for everyone.