Tamoxifen and raloxifene are the only FDA-approved drugs for breast cancer risk reduction in women at higher than average risk.
You may also hear the term “chemoprevention” to describe these drugs, but they are not chemotherapy drugs.
Tamoxifen is a hormone therapy drug used to both treat and prevent breast cancer. Raloxifene is only used to prevent breast cancer.
Both tamoxifen and raloxifene are pills.
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 (tamoxifen lowers risk by about 50 percent and raloxifene by about 38 percent) in women at high 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 right for all women at higher than average risk. For example, tamoxifen increases the risk of cataracts and cancer of the uterus .
Talk with your health care provider about the potential harms and benefits of these drugs.
Learn more about the side effects of tamoxifen.
Learn more about talking with your health care provider.
Other side effects are less common.
These effects occur mainly in older postmenopausal women.
Certain types of anti-depressants called selective serotonin reuptake inhibitors (SSRIs) can interfere with the metabolism of tamoxifen (how tamoxifen works in the body). However, it’s unlikely SSRIs impact the effectiveness of tamoxifen [319-320].
If you are taking an SSRI to treat depression or menopausal symptoms (such as hot flashes), talk with your health care provider about possible drug interactions.
Researchers are studying tamoxifen benefit for women who have a BRCA1 or BRCA2 gene mutation and choose not to have prophylactic mastectomy.
Tamoxifen may be better at preventing breast cancer in women with a BRCA2 mutation than in women with BRCA1 mutations [321-322]. Tamoxifen only reduces the risk of estrogen receptor-positive (ER-positive) cancers . BRCA2-related tumors are more likely than BRCA1-related tumors to be ER-positive .
Most of what we know about the potential benefits and harms of tamoxifen come from data on white women. At this time, there are few data about women of other ethnicities.
However, studies show black women are more likely than white women to suffer from some of the harmful health effects of tamoxifen [324-325].
Aromatase inhibitors are hormone therapy drugs used to treat estrogen receptor-positive breast cancer in postmenopausal women.
Findings from randomized controlled trials of postmenopausal women at high risk have shown the aromatase inhibitors exemestane and anastrozole may lower the risk of breast cancer by about half [216-217].
Unlike tamoxifen and raloxifene, exemestane and anastrozole do not appear to increase the risk of blood clots [216-217]. However, they can cause menopausal symptoms, a loss of bone density and other side effects [216-217,326-329].
The American Society for Clinical Oncology (ASCO) and the National Comprehensive Cancer Network (NCCN) list exemestane and anastrozole as risk-lowering drug options for postmenopausal women at higher risk of breast cancer. However, these drugs do not have FDA-approval for use in the risk reduction setting. They are only FDA-approved for use in breast cancer treatment.
Learn about aromatase inhibitors (including exemestane and anastrozole) and breast cancer treatment.
Learn more about the side effects of aromatase inhibitors.
The aromatase inhibitor drug letrozole (Femara) 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.
Learn more about emerging areas in breast cancer risk reduction.
If you are at higher than average risk of breast cancer and considering joining a clinical trial of risk-lowering drugs, discuss the potential risks and benefits with your health care provider.
BreastCancerTrials.org in collaboration with Susan G. Komen® offers a custom matching service to help you find clinical trials on risk reduction for healthy women and women at high risk of breast cancer.
Learn more about clinical trials.
Tamoxifen and raloxifene are generic drugs. Generic drugs cost less than the name brands, but are just as effective.
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.
The Affordable Care Act requires insurance plans (started on or after September 24, 2014) 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.
Read Komen’s statement applauding the government’s decision to cover these risk-lowering drugs.
Learn more about insurance plans, prescription drug assistance programs and other financial assistance resources.
*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.
Research Fast Facts: Breast Cancer Prevention
Facts for Life: Tamoxifen
Breast Cancer 101 - Side Effects of Tamoxifen