MedicalResearch:What is the background for this study?
Dr. Nichols: Tamoxifen, a drug that is often used to treat breast cancer, has also been approved to prevent breast cancer in women who may be at high risk for developing the disease. Taking tamoxifen for 5 years can lower breast cancer risk by up to 48%. The United States Federal Drug Administration (FDA) approved tamoxifen for breast cancer prevention more than 15 years ago (in 1998) for women ages 35 and older who are at high risk of breast cancer and who are at low risk for serious side effects.
National estimates show that <1% of women who are eligible to use tamoxifen actually use it for breast cancer prevention. While tamoxifen lowers breast cancer risk it does cause hot flashes and may lead to serious side effects such as cataract, stroke, and uterine cancer. Women who start taking tamoxifen may also stop taking it before the recommended 5-years due to side effects.
We used a tool developed by scientists at the National Cancer Institute (NCI) to calculate whether the benefits of tamoxifen outweighed the risks for women in the Sister Study, a study of more than 50,000 U.S. and Puerto Rican women with a family history of breast cancer. The tool uses information on a woman’s age, race, breast cancer risk, menopausal status, and whether she had a hysterectomy (surgical removal of the uterus) to estimate whether there is no, moderate or strong evidence that the benefits of tamoxifen will outweigh the risks.