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Report finds that medications effectively reduce risk of breast cancer, but can cause other problems

Research Activities, November 2009

Three drugs, including tamoxifen, reduce a woman's chance of getting breast cancer, but each drug carries distinct potential harms of its own, according to a new report from the Agency for Healthcare Research and Quality (AHRQ). Drugs to reduce the risk of breast cancer can be prescribed to women with a family history of breast cancer or other risk factors, but prescribing practices vary widely. The comparative effectiveness review found that all three drugs-tamoxifen, raloxifene, and tibolone-significantly reduce invasive breast cancer in midlife and older women who have not previously had breast cancer. However, the benefits and adverse effects can vary depending on the drug and the patient. The report is the first to make a direct, comprehensive comparison of the drugs so that women and their health care providers can assess the medications' potential effectiveness and adverse effects.

Tamoxifen, a selective estrogen receptor modulator (SERM), was approved by the U.S. Food and Drug Administration (FDA) in 1998 to prevent breast cancer in women at high risk of developing the disease. Tamoxifen's use to reduce the risk of breast cancer is accepted clinical practice, although the drug is primarily used for treatment rather than risk reduction. Raloxifene, another SERM, is primarily used to prevent and treat osteoporosis, and was approved by the FDA for breast cancer risk reduction in 2007. The third drug, tibolone, has not been approved by the FDA for use in the United States, but is commonly used in other countries to treat menopausal symptoms and osteoporosis. The most common side effects for tamoxifen are flushing and other vasomotor symptoms (e.g., night sweats, hot flashes), vaginal discharge and other vaginal symptoms such as itching or dryness. For raloxifene, side effects include vasomotor symptoms and leg cramps; and for tibolone, side effects include vaginal bleeding.

Adverse effects of tamoxifen include a greater risk for endometrial cancer, hysterectomies, and cataracts compared with the other drugs. Tamoxifen and raloxifene increase risk of blood clots, although tamoxifen's risk is greater. Tibolone carries an increased risk of stroke. The report also examined the drugs' effectiveness and harms based on such factors as age, menopausal status, estrogen use, and family history of breast cancer, and sought to identify the kinds of women who might be good candidates for prevention therapy, although the evidence is limited in this area. AHRQ's new report, Comparative Effectiveness of Medications to Reduce Risk of Primary Breast Cancer in Women, is the latest analysis from the Agency's Effective Health Care Program.� Information on the Program and the new report can be found at

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Page last reviewed November 2009
Internet Citation: Report finds that medications effectively reduce risk of breast cancer, but can cause other problems: Research Activities, November 2009. November 2009. Agency for Healthcare Research and Quality, Rockville, MD.