Breast Cancer

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Causes, Risk Factors, and Prevention TOPICS

Can breast cancer be prevented?

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 will be 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?").

Body weight, physical activity, and diet have all been linked to breast cancer, so these might be areas where you can take action.

Both increased body weight and weight gain as an adult are linked with a higher risk of breast cancer after menopause. Alcohol also increases risk of breast cancer. Even low levels of alcohol intake have been linked with an increase in risk.

Many studies have shown that moderate to vigorous physical activity is linked with lower breast cancer risk.

A diet that is rich in vegetables, fruit, poultry, fish, and low-fat dairy products has also been linked with a lower risk of breast cancer in some studies. But it is not clear if specific vegetables, fruits, or other foods can lower risk. Most studies have not found that lowering fat intake has much of an effect on breast cancer risk.

At this time, the best advice about diet and activity to possibly reduce the risk of breast cancer is to:

  • Get regular, intentional physical activity.
  • Reduce your lifetime weight gain by limiting your calories and getting regular physical activity.
  • Avoid or limit your alcohol intake.

For more information, see our document, American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Prevention.

Women who choose to breastfeed for at least several months may also get an added benefit of reducing their breast cancer risk.

Not using hormone therapy after menopause can help you avoid raising your risk.

It’s not clear at this time if environmental chemicals that have estrogen-like properties (like those found in some plastic bottles or certain cosmetics and personal care products) increase breast cancer risk. 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 the American Cancer Society's guidelines for early detection (outlined in the section, "Can breast cancer be found early?"). Early detection will not prevent breast cancer, but it can help find it 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 your risk and how much any of these approaches might lower this risk.

Genetic testing for BRCA gene mutations

Many women may have relatives with breast cancer, but in most cases this is not the result of BRCA gene mutations. Genetic testing for these mutations can be 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.

Different expert groups have different recommendations about who should be considered for genetic testing.

For example, the U.S. Preventive Services Task Force (USPSTF) has guidelines aimed at women without a history of cancer. The USPSTF recommends that women with an increased risk of having a BRCA mutation based on a family history of breast, ovarian, fallopian tube, and/or primary peritoneal cancer should be referred to a genetics professional about testing. The genetics professional can evaluate that risk further, discuss the pros and cons of testing if the woman is at high risk (this is called genetic counseling), and arrange for the test if the patient wished to proceed. It is important to realize that BRCA mutations are rare, and only a small fraction of women who have a family history of breast cancer should be referred for genetic counseling and testing.

Other medical groups offer guidelines that include women with cancer. For example, the National Comprehensive Cancer Network guidelines advise referring women 60 and under who have triple-negative breast cancer for genetic counseling and testing.

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.

Most large cancer centers employ a genetic counselor who will assess your risk of carrying a mutated BRCA gene, explain the risks and benefits of testing, and check with your insurance company to see if they will cover the test.

For more information, see our document, Genetic Testing: What You Need to Know. You might also want to visit the National Cancer Institute Web site.

Breast cancer chemoprevention

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

Tamoxifen: Tamoxifen 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?").

Tamoxifen can also lower the risk of getting breast cancer in women who are at increased risk for the disease. It seems to affect the risk of breast cancers that are estrogen receptor−positive (ER-postive), but not those that are estrogen receptor−negative (ER-negative). Most breast cancers that occur in women after menopause are ER-positive.

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 by the US Food and Drug Administration (FDA) for reducing breast cancer risk in women at high risk. It can be used in women even if they haven’t gone through menopause.

Tamoxifen has side effects that include increased risks of endometrial (uterine) cancer (in women who have gone through menopause) and serious blood clots, so women should consider the possible benefits and risks of tamoxifen before deciding if it is right for them.

Tamoxifen seems to reduce breast cancer risk in women with BRCA2 gene mutations who have never had breast cancer, but the same may not be true for those with BRCA1 mutations.

Raloxifene: Like tamoxifen, raloxifene (Evista®) 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 nearly as well as tamoxifen in reducing the risk of invasive breast cancer and non-invasive cancer (DCIS). Raloxifene also had 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). Like tamoxifen, it only lowers the risk of ER-postive breast cancer and not ER-negative tumors.

Raloxifene is FDA 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 (Arimidex®), letrozole (Femara®), and exemestane (Aromasin®) are also being studied as breast cancer chemopreventive agents in post-menopausal women. These drugs, called aromatase inhibitors, 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. A recent study showed exemestane can lower the risk of invasive breast cancer by 65% in post-menopausal women who have an increased risk for breast cancer. Like tamoxifen and raloxifene, exemestane lowered the risk of breast cancers that are ER-positive, but not those that are ER-negative.

Exemestane and the other aromatase inhibitors can also have side effects, such as joint pain and stiffness. These drugs also can cause bone loss, leading to a higher risk of osteoporosis and even broken bones. None of these drugs is currently FDA-approved for reducing the risk of developing breast cancer.

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. Studies have also looked to see if drugs called bisphosphonates may lower the risk of breast cancer. Bisphosphonates are mainly used to treat osteoporosis, but they are also used to treat breast cancer that has spread to the bone. These, as well as several other drugs and dietary supplements, are being studied to see if they can lower breast cancer risk, but none is 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?" For more information on the possible benefits and risks of chemopreventive drugs see our 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, surgery to remove the breasts or ovaries may be an option.

Preventive (prophylactic) mastectomy: Removing both breasts before cancer is diagnosed can greatly reduce the risk of breast cancer (by up to 97%). Some women diagnosed with cancer in one breast choose to have the other, healthy breast removed as well to prevent a second breast cancer. Breast removal 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
  • Strong family history (breast cancer in several close relatives)
  • Lobular carcinoma in situ (LCIS) seen on biopsy
  • Previous cancer in one breast (especially in someone with a strong family history)

This type of surgery has been shown to be helpful in studies of large groups of women with certain conditions, but there is no way to know ahead of time if this surgery will benefit any one woman. Some women with BRCA mutations will develop breast cancer early in life, and have a very high risk of getting a second breast cancer. 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, but they would still have to deal with its aftereffects.

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 likely because the surgery removes the main sources of estrogen in the body (the ovaries).

It is important that women with a BRCA mutation recognize they also have a high risk of developing ovarian cancer. Most doctors recommend that women with BRCA mutations have their ovaries surgically removed once they finish having children to lower this risk.


Last Medical Review: 09/11/2013
Last Revised: 01/31/2014