Tamoxifen and raloxifene are the only two drugs FDA-approved for breast cancer risk reduction in women at higher risk.
You may also hear the term “chemoprevention” to describe these drugs. Please note, these drugs are not chemotherapy drugs. Tamoxifen is a hormone therapy drug used to both treat and prevent breast cancer. Raloxifene is only used in the prevention setting and not for breast cancer treatment.
Both tamoxifen and raloxifene are taken in pill form.
For a summary of research studies on tamoxifen and raloxifene and breast cancer prevention, visit the Breast Cancer Research Studies section.
Both tamoxifen and raloxifene can lower the risk of :
Tamoxifen and raloxifene only reduce the risk of estrogen receptor-positive breast cancers. Neither drug reduces the risk of estrogen receptor-negative cancers .
Tamoxifen is more effective than raloxifene in lowering breast cancer risk. However, raloxifene has fewer harmful side effects than tamoxifen (see table below) . This makes raloxifene a better choice for some women.
Tamoxifen and raloxifene have some long-term side effects (see table below) and may not be suitable for all women at higher risk. For example, tamoxifen increases the risk of cataracts and cancer of the uterus . Talk to your health care provider about the potential harms and benefits of these drugs.
Learn more about talking to your health care provider.
Who can take the drug?
What are common short-term side effects?
Other side effects are less common.
What are the possible health risks?
These effects occur mainly in older postmenopausal women.
These effects occur mainly in older postmenopausal women.
What about use in breast cancer treatment?
Effective in the treatment of hormone receptor-positive breast cancer.
Has not been shown to be effective for the treatment of breast cancer.
Adapted from selected sources [156,264-271].
*Please note, the information provided within Komen Perspectives articles is only current as of the date of posting. Therefore, some information may be out of date at this time.
Researchers are studying whether tamoxifen lowers the risk of breast cancer in women who have a BRCA1 or BRCA2 gene mutation [273-275]. Some studies have suggested that tamoxifen may be more effective in preventing breast cancer in BRCA2 carriers than BRCA1 carriers [274-276]. Tamoxifen only reduces the risk of estrogen receptor-positive cancers. BRCA2-related tumors are more likely than BRCA1-related tumors to be estrogen receptor-positive .
Some findings have shown tamoxifen might offer benefit to BRCA1/2 carriers who have been diagnosed with breast cancer in the past [125,273,275-276]. One study found the risk of breast cancer in the unaffected (opposite) breast may be reduced by 62 to 67 percent with tamoxifen use .
Although we know much about the potential benefits and harms of tamoxifen for white women, at this time, there are few data for women of other ethnicities.
African-American women may get less benefit and more harm from tamoxifen than white women. African-American women have a lower rate of breast cancer than white women and are more likely to suffer some of the harmful health effects of tamoxifen [278-279].
Aromatase inhibitors are hormone drugs that are part of standard treatment for estrogen receptor-positive breast cancer in postmenopausal women (learn more). There are three aromatase inhibitors that are FDA-approved for the treatment of breast cancer in the U.S.: anastrozole (Arimidex), letrozole (Femara) and exemestane (Aromasin). They appear to be equally effective in treating breast cancer.
Aromatase inhibitors are now being studied to see whether they may lower breast cancer risk in postmenopausal women at high risk.
Findings from randomized controlled trials of cancer-free postmenopausal women at high risk have shown that the aromatase inhibitors exemestane and anastrozole may lower the risk of breast cancer by about half .
Unlike tamoxifen and raloxifene, exemestane and anastrozole do not appear to increase the risk of blood clots [157,280]. However, exemestane, anastrozole and other aromatase inhibitors can cause menopausal symptoms, a loss of bone density and other side effects (learn more) [281-284].
The American Society for Clinical Oncology (ASCO) and the National Comprehensive Cancer Network (NCCN) now list exemestane and anastrozole as risk-lowering drug options for postmenopausal women at higher risk of breast cancer. However, these drugs do not yet have FDA-approval for use in the risk reduction setting. These drugs are only FDA-approved for use in breast cancer treatment.
Learn about aromatase inhibitors (including exemestane and anastrozole) and breast cancer treatment.
Learn about the side effects of aromatase inhibitors.
The aromatase inhibitor drug letrozole is also being studied to see whether it may lower risk in postmenopausal women at high risk of breast cancer.
Learn about aromatase inhibitors and breast cancer treatment.
Other drugs currently used to treat breast cancer are under study for use in risk reduction and new risk-lowering drugs are being developed.
If you are at higher risk of breast cancer and are considering joining a clinical trial of risk-lowering drugs, discuss the potential risks and benefits of these drugs with your health care provider.
Learn more about emerging areas in breast cancer risk reduction.
Learn more about clinical trials.
Medicare and many insurance providers offer prescription drug plans. One may already be included in your policy or you may be able to buy an extra plan for prescriptions. You may also qualify for assistance from programs that help with drug costs or offer low-cost or free prescriptions.
Tamoxifen is available in a generic form (cheaper than the name brand).
Starting September 24, 2014, the Affordable Care Act requires new insurance plans to cover the cost (with no co-payments) of tamoxifen and raloxifene for women at high risk of breast cancer. Learn more about this coverage and the Affordable Care Act. Read Komen’s statement applauding the government’s decision to cover these risk-lowering drugs.
Learn more about insurance plans and prescription drug assistance programs.
Komen Support Resources
Research Fast Facts: Prevention
Facts for Life: Tamoxifen
Breast Cancer 101 - Side Effects of Tamoxifen