Epidemiology, prevention, and early detection of breast cancer.

Breast cancer is a leading women's health issue. Continued advances in understanding the temporal sequencing of relevant exposures promises to shed light on the continuum of breast carcinogenesis. Oral contraceptive use and the transient increase in risk following childbirth are exposures that affect the near-term risk of breast cancer. The availability of commercial testing for inherited susceptibility to breast cancer has accelerated the need for data to develop sound policy for implementing gene testing. The risks associated with BRCA1 and BRCA2 mutations may be less than previously estimated. Antiestrogens with lesser risks than tamoxifen hold promise for chemoprevention, but await testing. Not enough is known to formulate primary prevention strategies based on lifestyle interventions. Further understanding lifestyle factors that may be involved in the etiology of breast cancer and are amenable to preventive intervention thus remains a top priority, with diet and physical activity of greatest interest.