Although we know some of the risk factors linked to breast cancer, we do not yet know what causes most breast cancer. It could be that a woman of average risk for breast cancer might lower her risk somewhat by changing those risk factors that can be changed. These include giving birth to several children and breast feeding them for several months, not drinking alcohol, exercising regularly, and staying slim. It is also important for women to follow the American Cancer Society’s guidelines for finding breast cancer early. (See the section, "How Is Breast Cancer Found?")
There are tests that can tell if a woman has certain changed genes linked to breast cancer. With this information, women can then take steps to reduce their risk. We strongly recommend genetic counseling before taking these tests and before making any decisions about preventive measures.
The drug tamoxifen has been used for many years as a treatment for some types of breast cancer. Recent studies show that women at high risk for breast cancer are less likely to get the disease if they take tamoxifen. Another drug, raloxifene, is also being studied for use in reducing breast cancer risk. And there are even newer drugs now under study.
In some rare cases, women at very high risk of breast cancer might consider a preventive (prophylactic) mastectomy. This is an operation in which one or both breasts are removed before there is any known breast cancer. The reasons for thinking about this type of surgery need to be very strong. Women should get a second opinion before making a decision to have this type of surgery.
American Cancer Society website: http://www.cancer.org