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 to lower the risk of breast cancer, not to treat it.
Both tamoxifen and raloxifene are taken in pill form.
Tamoxifen and Raloxifene
Breast cancer risk
Both tamoxifen and raloxifene can lower the risk of [178]:
Tamoxifen and raloxifene only reduce the risk of estrogen receptor-positive breast cancers. Neither drug reduces the risk of estrogen receptor-negative cancers [178].
Tamoxifen is more effective than raloxifene in lowering breast cancer risk. However, raloxifene has fewer harmful side effects than tamoxifen (see table below) [178]. This makes raloxifene a better choice for some women.
Side effects
Tamoxifen and raloxifene have some long-term side effects (see table below) and may not be right for all women at higher risk. For example, tamoxifen increases the risk of cataracts and cancer of the uterus [178].
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.
Tamoxifen versus raloxifene| | Tamoxifen | Raloxifene |
|---|
| Who can take the drug? | - Premenopausal who are ages 35 and older
- Postmenopausal women
| - Postmenopausal women only
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| What are common short-term side effects? | - Hot flashes
- Irregular periods or spotting (uterine bleeding)
- Vaginal discharge
- Vaginal dryness or itching
Other side effects are less common. |
|
| What are the possible health risks? | - Blood clots in the large veins (deep venous thrombosis)
- Blood clots in the lungs (pulmonary emboli)
- Cancer of the uterus or endometrium (lining of the uterus)
- Cataracts
- Stroke
These effects occur mainly in older postmenopausal women. | - Blood clots in the large veins (deep venous thrombosis)
- Blood clots in the lungs (pulmonary emboli)
- Stroke
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 breast cancer treatment. |
| Adapted from selected sources [178,265-272]. |
*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.
Certain types of anti-depressants called selective serotonin reuptake inhibitors (SSRIs) can interfere with the metabolism of tamoxifen (how tamoxifen works in the body) [145,273].
If you are taking SSRIs to treat depression or menopausal symptoms (such as hot flashes), talk with your health care provider about possible drug interactions and other treatment options.
Researchers are studying tamoxifen use in women who have a BRCA1 or BRCA2 gene mutation.
Some findings suggest that tamoxifen may be more effective in preventing breast cancer in BRCA2 carriers than in BRCA1 carriers [152,274]. 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 [152,275].
Tamoxifen may offer benefit to BRCA1/2 carriers who have been diagnosed with breast cancer in the past [148,267-277]. One study found the risk of breast cancer in the unaffected (opposite) breast may be reduced by 62 to 67 percent with tamoxifen use [277].
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 for women of other ethnicities.
However, studies show African-American women are more likely than white women to suffer from 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). Anastrozole (Arimidex), letrozole (Femara) and exemestane (Aromasin) are aromatase inhibitors.
These drugs are now being studied to see whether they may lower breast cancer risk in postmenopausal women at high risk.
Exemestane (Aromasin) and anastrozole (Arimidex)
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 [179,280].
Unlike tamoxifen and raloxifene, exemestane and anastrozole do not appear to increase the risk of blood clots [179,280]. However, they 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.
Other 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.
| Komen Support Resources |
- Calls to our breast care helpline 1-877 GO KOMEN (1-877-465-6636) are answered by a trained and caring staff member Monday through Friday from 9:00 a.m. to 10:00 p.m. ET and from 6:00 a.m. to 7:00 p.m. PT. Our helpline provides free, professional support services to anyone with breast cancer questions or concerns, including breast cancer survivors and their families. You can also email the breast care helpline at [email protected].
- Our Message Boards offer online forums to share your thoughts or feelings about subjects related to breast cancer. Our Women at Higher Risk of Breast Cancer forum within the Message Boards offers women at higher risk a place to share their own unique experiences and challenges.
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