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Risk-Lowering Drugs

Tamoxifen and raloxifene are the only FDA-approved drugs for breast cancer risk reduction in women who do not have breast cancer, but are at higher risk.

You may hear the term “chemoprevention” to describe these drugs, but they aren’t chemotherapy drugs.

  • Tamoxifen is used to prevent and treat breast cancer.
  • Raloxifene is used to prevent breast cancer. (Raloxifene is also used to prevent and treat osteoporosis.)

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.

Tamoxifen and raloxifene

In women who don’t have breast cancer, but are at higher risk of breast cancer, tamoxifen and raloxifene can be used to lower risk.

Breast cancer risk

Both tamoxifen and raloxifene can lower the risk of [232]:

  • Invasive breast cancer
  • Non-invasive breast cancer, such as ductal carcinoma in situ (DCIS)

Tamoxifen and raloxifene only reduce the risk of estrogen receptor-positive breast cancers. Neither drug reduces the risk of estrogen receptor-negative cancers [232].

Tamoxifen is more effective than raloxifene in lowering breast cancer risk [232]. Tamoxifen lowers risk by about 50% in women at high risk [232]. Raloxifene lowers risk by about 38% in women at high risk [232]. However, raloxifene has fewer harmful side effects than tamoxifen (see table below) [232]. This makes raloxifene a better choice for some women.

Side effects

Both 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 [232].

Talk with your health care provider about the possible benefits and harms of these drugs.

Learn more about the side effects of tamoxifen.

Learn more about talking with your health care provider.

Tamoxifen versus raloxifene for breast cancer risk reduction

Tamoxifen

Raloxifene

Who can take the drug?

  • Premenopausal women ages 35 and older
  • Postmenopausal women

  • Postmenopausal women only

How is the drug taken?

  • A pill taken once a day for 5 years

  • A pill taken once a day for 5 years

What are common short-term side effects?

  • Hot flashes
  • Irregular periods or spotting (uterine bleeding)
  • Leg cramps
  • Vaginal discharge
  • Vaginal dryness or itching

Other side effects are less common.

  • Hot flashes
  • Leg cramps

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 (the lining of the uterus)
  • Cataracts
  • Stroke

These effects occur mostly in older postmenopausal women.

  • Blood clots in the large veins (deep venous thrombosis)
  • Blood clots in the lungs (pulmonary emboli)
  • Stroke

These effects occur mostly in older postmenopausal women.

What about use in breast cancer treatment?

Effective in the treatment of hormone receptor-positive breast cancer

Not effective for breast cancer treatment

Adapted from selected sources [232,371-376].

 

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Some types of anti-depressants called selective serotonin reuptake inhibitors (SSRIs) can interfere with how tamoxifen works in the body. However, it’s unlikely SSRIs impact the effectiveness of tamoxifen [377-378].

If you’re 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 the benefit of tamoxifen for women who have a BRCA1 or BRCA2 inherited gene mutation and choose not to have risk-reducing mastectomy.

Tamoxifen may be better at preventing breast cancer in women with a BRCA2 gene mutation than in women with BRCA1 gene mutations [201]. Tamoxifen only reduces the risk of estrogen receptor-positive (ER-positive) cancers [232]. BRCA2-related tumors are more likely than BRCA1-related tumors to be ER-positive [201].

Most of what we know about the potential benefits and harms of tamoxifen come from data on white women. There are few data on women of other races or ethnicities.

However, some older studies show Black women are more likely than white women to suffer from some of the harmful health effects of tamoxifen [379-380].

Aromatase inhibitors are hormone therapy drugs used to treat estrogen receptor-positive breast cancer in postmenopausal women. Aromatase inhibitors are pills.

Exemestane (Aromasin) and anastrozole (Arimidex)

Exemestane and anastrozole are aromatase inhibitor drugs. Findings from randomized controlled trials of postmenopausal women at high risk have shown exemestane and anastrozole may reduce the risk of breast cancer by about half [233-234].

Unlike tamoxifen and raloxifene, exemestane and anastrozole don’t appear to increase the risk of blood clots [233-234]. However, they can cause menopausal symptoms, a loss of bone density and other side effects [233-234,381-384].

The American Society for Clinical Oncology (ASCO), the National Comprehensive Cancer Network (NCCN) and the U.S. Preventive Services Task Force list exemestane and anastrozole as risk-lowering drug options for postmenopausal women who do not have breast cancer, but are at high risk of breast cancer. 

However, exemestane and anastrozole aren’t FDA-approved 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.

Other aromatase inhibitors

The aromatase inhibitor drug letrozole (Femara) is under study to see whether it lowers breast cancer risk in postmenopausal women at high risk.

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’re at higher 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.

Susan G. Komen® Breast Care Helpline

If you or a loved one needs information or resources about clinical trials, call the Komen Breast Care Helpline at 1-877 GO KOMEN (1-877- 465- 6636) or email clinicaltrialinfo@komen.org.

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BreastCancerTrials.org in collaboration with Susan G. Komen® offers a custom matching service to help clinical trials on risk reduction.

Learn more about clinical trials. 

Generic drugs are available for tamoxifen and raloxifene. Generic drugs cost less than name brand drugs but are just as effective.

Medicare and many insurance companies 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. Other programs 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.

Learn more about insurance plans, prescription drug assistance programs and other financial assistance resources.

 

Susan G. Komen® Support 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.

Updated 04/04/23