Early detection, epidemiology, and prevention of breast cancer.

Control of breast cancer will ultimately be achieved through a better understanding of the epidemiology of the disease and application of primary prevention. Until then, use of screening mammography offers the promise of a 30% reduction in breast cancer mortality, which continues to be shown by screening studies with prolonged follow-up. Biologic markers of cancer risk, including nipple aspirates and cyst fluid, suggest that a complete risk profile can be developed using fluid and tissue obtained from the normal breast. Epidemiologic studies of dietary factors and geographic differences in breast cancer risk continue to provide promising leads relating to the etiology of the disease. Increasing evidence suggests that circulating androgens and estrogens affect breast cancer risk, whereas exogenous estrogen therapy does not increase risk except for small subgroups of women at risk. Increasing understanding of the genetics of breast cancer will have an impact on the disease in the near future. The greatest impact in the short term will come from the use of tamoxifen for primary prevention of breast cancer. The retinoids, particularly N-(4-hydroxyphenyl)retinamide, hold great promise as agents for primary prevention.