Other than these lifestyle changes, the most important action a woman can take is to follow early detection guidelines. Following the American Cancer Society's guidelines for early detection (outlined in the section, "Can Breast Cancer Be Found Early?") will not prevent breast cancer, but it can help find cancers when the likelihood of successful treatment is greatest.

If you are a woman with a strong family history of breast cancer, with a known genetic mutation of a BRCA gene, or if you have had DCIS, LCIS, or biopsies that have shown pre-cancerous changes, there may be some additional things you can do to reduce your chances of developing breast cancer.

While many women have relatives affected by breast cancer, in most cases this is not the result of BRCA gene mutations. Genetic testing for these mutations can be complicated and expensive and can have a wide range of consequences that need to be considered. Therefore it should only be done when there is a reasonable suspicion that a mutation may be present. Genetic counseling is strongly recommended before any testing is done. (For more information, see the separate American Cancer Society document, Genetic Testing: What You Need to Know.)

Recently the US Preventive Services Task Force recommended that only women with a strong family history be evaluated for genetic testing for BRCA mutations. This group represents only about 2% of adult women in the United States.

Women who are not of Ashkenazi (Eastern European) Jewish heritage should be referred for genetic evaluation if they have any of the following:

• two first-degree relatives (mother, sisters, daughters) with breast cancer, one of whom was diagnosed when they were younger than 50 
• three or more first- or second-degree relatives (includes grandmothers, aunts, cousins) diagnosed with breast cancer 
• both breast and ovarian cancer among first- and second-degree relatives 
• a first-degree relative diagnosed with cancer in both breasts 
• two or more first- or second-degree relatives diagnosed with ovarian cancer 
• a male relative with breast cancer

Women of Ashkenazi (Eastern European) Jewish heritage should be referred for genetic evaluation if they have:

• a first-degree relative with breast or ovarian cancer 
• two second-degree relatives on the same side of the family with breast or ovarian cancer

Breast Cancer Chemoprevention

Chemoprevention is the use of drugs to reduce the risk of cancer. Several drugs have been studied for use in lowering breast cancer risk.

Tamoxifen: Tamoxifen is a drug that blocks some of the effects of estrogen on breast tissue. It has already been used for many years to reduce the risk of recurrence in localized breast cancer and as a treatment for advanced breast cancer (see the section, "How Is Breast Cancer Treated?"). Several studies have found that tamoxifen can also lower the risk of getting breast cancer in women known to be at increased risk for the disease.

Results from the Breast Cancer Prevention Trial (BCPT) have shown that women at increased risk for breast cancer are less likely to develop the disease if they take tamoxifen. Women in the study were assigned to take either tamoxifen or a placebo pill for 5 years. After 7 years of follow-up, women taking tamoxifen had 42% fewer breast cancers than women who took the placebo, although there was no difference in the risk of death due to breast cancer. Thus far, tamoxifen is the only drug approved for use in reducing breast cancer risk in high-risk women.

Because tamoxifen has side effects that include increased risks of endometrial (uterine) cancer and blood clotting, women should consider the possible benefits and risks of tamoxifen before deciding whether or not it is right for them.

If you are going to be taking tamoxifen because you have been found to have a BRCA mutation, it is important to know if your mutation is in the BRCA1 or BRCA2 gene. BRCA1-related cancers may not be prevented by tamoxifen.

Raloxifene: Like tamoxifen, raloxifene also blocks the effect of estrogen on breast tissue. A study comparing the effectiveness of the 2 drugs, called the Study of Tamoxifen and Raloxifene (STAR) trial, found that raloxifene reduced the risk of invasive breast cancer to the same degree as tamoxifen, although it didn't have the same protective effect against non-invasive cancer (DCIS or LCIS). Raloxifene did, however, have lower risks of certain side effects such as uterine cancer and blood clots in the legs or lungs, compared to tamoxifen (although the risk of blood clots was still higher than normal).

Raloxifene is approved to help reduce breast cancer risk in women past menopause who have osteoporosis (bone thinning) or are at high risk for breast cancer.

Aromatase inhibitors: Drugs such as anastrozole, letrozole, and exemestane are also being studied as breast cancer chemopreventive agents in post-menopausal women. These drugs are already being used to help prevent breast cancer recurrences. They work by blocking the production of small amounts of estrogen that post-menopausal women normally make. But they can also have side effects, such as causing joint pain and stiffness and bone loss, leading to a higher risk of osteoporosis. None of these drugs is approved for reducing breast cancer risk at this time.

Other drugs: New studies are under way using other drugs as well. Some studies have found that women who take aspirin or non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen seem to have a lower risk of breast cancer. Similar drugs (called COX-2 inhibitors) are being tested to see if they can reduce the risk of breast cancer in women who are at a high risk for this disease, although recent studies have shown that these drugs can raise the risk of heart attacks. None of these drugs is approved for reducing breast cancer risk at this time.

Many of the drugs mentioned above are discussed further in the section, "How Is Breast Cancer Treated?", under hormonal treatment. For more information on the possible benefits and risks of chemopreventive drugs see the separate American Cancer Society document, Medicines to Reduce Breast Cancer Risk.

For the few women who are at very high risk for breast cancer, prophylactic surgery such as bilateral (double) mastectomy may be an option.

Preventive (prophylactic) mastectomy: This surgery can greatly reduce (but not eliminate) the risk of breast cancer by removing both breasts before cancer is diagnosed. Some of the reasons for considering this type of surgery may include:

• mutated BRCA genes found by genetic testing 
• previous cancer in one breast 
• strong family history (breast cancer in several close relatives) 
• biopsy specimens showing lobular carcinoma in situ (LCIS)

There is no way to know ahead of time whether this surgery will benefit a particular woman. Some women with BRCA mutations will develop a fatal breast cancer early in life, and a prophylactic mastectomy before the cancer occurs might add many years to their lives. But while most women with BRCA mutations develop breast cancer, some don't. These women would not benefit from the surgery, although they would still have to deal with its after effects.

While this operation removes nearly all of the breast tissue, a small amount remains. So although this operation markedly reduces the risk of breast cancer, a cancer can still develop in the breast tissue remaining after surgery. To date, this has been a rare problem.

Second opinions are strongly recommended before any woman makes the decision to have this surgery. The American Cancer Society Board of Directors has stated that "only very strong clinical and/or pathologic indications warrant doing this type of preventive operation." Nonetheless, after careful consideration, this might be the right choice for some women.

Prophylactic oophorectomy (ovary removal): Women with a BRCA mutation who have their ovaries surgically removed may reduce their risk of breast cancer by 50% or more. This is because the surgery removes the main sources (the ovaries) of estrogen in the body.

Although this document is not about ovarian cancer, it is important that women with a BRCA mutation recognize they also have a high risk of developing ovarian cancer. Most doctors recommend that these women have their ovaries surgically removed once child bearing is complete.