Women should discuss with their health care provider their individual risks and the potential benefits of taking tamoxifen. However, women at increased risk for blood clots and those who are pregnant or who plan to become pregnant should not take tamoxifen. Animal studies have suggested that the use of tamoxifen during pregnancy might harm the fetus. Women taking any birth control pills or hormone replacements must stop those medications before beginning tamoxifen. Premenopausal women who take tamoxifen should use some method of birth control other than birth control pills.
Tamoxifen is the only proven way to reduce the risk of breast cancer.
Studies of other ways to prevent breast cancer are under way and planned. The study will compare tamoxifen with raloxifene, an osteoporosis drug which may also have breast cancer prevention effects. STAR will enroll 22,000 high-risk women and is scheduled to begin at centers across the United States and in Canada in early 1999. The Breast Cancer Risk Assessment Tool gives an estimated risk. There is also some doubt about whether women from other countries will have accurate results because the tool is based on U.S. women.