Several methods show promise in reducing breast cancer risk. In October 1998, the Food and Drug Administration approved the drug tamoxifen to lower the risk of breast cancer in high-risk women. Following a large-scale study, researchers found that tamoxifen reduced cancer in high-risk women by about 50 percent.  Another method is a type of surgery called preventive or prophylactic mastectomy for women at high risk of breast cancer. It involves removing a breast that is not known to contain cancer in order to reduce a woman's cancer risk.