Chemoprevention of breast cancer for women at high risk.

Breast cancer remains the second most common cause of cancer death in the United States. Several studies have identified cohorts of women at higher than average risk to develop this disease. These are women who are exposed to high levels of endogenous or exogenous estrogens, those with a family history of breast cancer, and those who harbor benign breast disease or genetic mutations that predispose to breast cancer. In this population group, adapting a chemoprevention strategy to decrease the risk of developing overt disease is a strong consideration. To this end, tamoxifen is the most studied agent to date. This article describes high-risk categories that predict future development of invasive breast cancer, summarizes the currently available data to support the use of tamoxifen for chemoprevention, and discusses the adverse effects of tamoxifen, as well as measures to anticipate and monitor for possible adverse outcomes.