Chemoprevention is a term used to describe the use of drugs to lower the risk of breast cancer in women at higher risk. Tamoxifen and raloxifene are the only two drugs FDA-approved for breast cancer chemoprevention.
Please note, these drugs are not chemotherapy drugs. Tamoxifen is a hormone therapy drug used for both breast cancer treatment and prevention. 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 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?
Premenopausal (ages 35 and older) and postmenopausal women
Postmenopausal women only
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 [151,263-270].
Read our perspective on risk-lowering drugs (March 2012).*
*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 Therefore, some information may be out of date at this time.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 assessing whether tamoxifen lowers the risk of breast cancer in women who have a BRCA1 or BRCA2 gene mutation [248,272-273]. Some studies have suggested that tamoxifen may be more effective in preventing breast cancer in BRCA2 carriers than BRCA1 carriers [273-275]. BRCA2-related tumors are more likely to be estrogen receptor-positive . Tamoxifen works by attaching to estrogen receptors and only reduces the risk of estrogen receptor-positive cancers.
Some findings have shown tamoxifen might offer benefit to BRCA1/2 carriers who have been diagnosed with breast cancer in the past [115,272,275]. The risk of breast cancer in the unaffected (opposite) breast may be reduced by as much as 75 percent with two to four years of tamoxifen use .
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.
These drugs 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 (Aromasin) and anastrozole (Arimidex) may lower the risk of breast cancer by about half [152,525].
Unlike tamoxifen and raloxifene, exemestane and anastrozole do not appear to increase the risk of blood clots [152,525]. However, exemestane, anastrozole and other aromatase inhibitors can cause menopausal symptoms, a loss of bone density and other side effects [278-281].
The American Society for Clinical Oncology (ASCO) and the National Comprehensive Cancer Network (NCCN) now recommend exemestane as a risk-lowering drug option for postmenopausal women at higher risk of breast cancer. (These recommendations were made before the findings on anastrozole were published.) However, exemestane and anastrozole do not yet have FDA approval for use in the chemoprevention setting. These drugs are only FDA-approved for use in breast cancer treatment.
Learn about exemestane, 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 prevention 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 with your health care provider.
Learn more about emerging areas in chemoprevention.
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. And, you may 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 will require 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