There is no sure way to prevent breast cancer. But there are things all women can do that might reduce their risk and help increase the odds that if cancer does occur, it is found at an early, more treatable stage.

Lowering your risk

You can lower your risk of breast cancer by changing those risk factors that can be changed (see the section, "What are the risk factors for breast cancer?"). If you limit alcohol intake, exercise regularly, and maintain a healthy body weight, you are decreasing your risk of getting breast cancer. Women who choose to breast-feed for at least several months may also get an added benefit of reducing their breast cancer risk.

Not using post-menopausal hormone therapy (PHT) can help you avoid raising your risk.

Whether or not environmental chemicals that have estrogen-like properties (such as those found in some plastic bottles or certain cosmetics and personal care products) increase breast cancer risk is not clear at this time. If there is an increased risk, it is likely to be very small. Still, women who are concerned may choose to avoid products that contain these substances when possible.

Finding breast cancer early

Other than 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.

For women who are or may be at increased risk

If you are a woman at increased risk for breast cancer (for example, because you have a strong family history of breast cancer, a known genetic mutation of a BRCA gene, or you have had DCIS, LCIS, or biopsies that have shown pre-cancerous changes), there may be some things you can do to reduce your chances of developing breast cancer. Before deciding which, if any, of these may be right for you, talk with your doctor to understand what your risk is and how much any of these approaches might lower this risk.

Genetic testing for BRCA gene mutations

Although many women may have relatives with breast cancer, in most cases this is not the result of BRCA gene mutations. Genetic testing for these mutations can expensive and the results are often not clear cut. Testing can have a wide range of consequences that need to be considered. It should only be done when there is a reasonable suspicion that a mutation may be present.

The U.S. Preventive Services Task Force (USPSTF) recommends 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.

The USPSTF recommends that 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) 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

If you are considering genetic testing, it is strongly recommended that you talk first to a genetic counselor, nurse, or doctor qualified to explain and interpret the results of these tests. It is very important to understand what genetic testing can and can't tell you, and to carefully weigh the benefits and risks of testing before these tests are done. Testing is expensive and may not be covered by some health insurance plans.

For more information, see the separate American Cancer Society document, Genetic Testing: What You Need to Know. You may also want to visit the National Cancer Institute web site (www.cancer.gov/cancertopics/Genetic-Testing-for-Breast-and-Ovarian-Cancer-Risk).

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 been used for many years to reduce the risk of recurrence in localized breast cancer and as a treatment for advanced breast cancer when the tumor is estrogen-receptor positive (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 who are 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 took 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 dying from breast cancer. Tamoxifen is approved for reducing breast cancer risk in women at high risk.

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 if it is right for them.

Although tamoxifen seems to reduce breast cancer risk in women with BRCA2 gene mutations, the same may not be true for those with BRCA1 mutations.

Raloxifene: Like tamoxifen, raloxifene also blocks the effect of estrogen on breast tissue. A study comparing the effectiveness of the 2 drugs in women after menopause, called the Study of Tamoxifen and Raloxifene (STAR) trial, found that raloxifene worked as well as tamoxifen in reducing the risk of invasive breast cancer, 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 the risk of developing breast cancer at this time.

Other drugs: Studies are looking at other drugs as well. For example, 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. These, as well as several other drugs and dietary supplements, are being studied to see if they can lower breast cancer risk, although none are approved for reducing breast cancer risk at this time.

Many of the drugs mentioned here are discussed further in the section, "How is breast cancer treated?" in the section on hormone therapy. 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.

Preventive surgery for women with very high breast cancer risk

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

Preventive (prophylactic) bilateral mastectomy: Removing both breasts before cancer is diagnosed can greatly reduce the risk of breast cancer (by up to 97%). It does not completely prevent breast cancer because even a very careful surgeon will leave behind at least a few breast cells. The cells can go on to become cancerous. 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 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.

Second opinions are strongly recommended before any woman decides 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 may reduce their risk of breast cancer by 50% or more by having their ovaries surgically removed before menopause. This is because the surgery removes the main sources of estrogen in the body (the ovaries).

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 they finish having children.

Last Medical Review: 09/18/2009
Last Revised: 09/18/2009