BREAST-CANCER CHEMOPREVENTION - TAMOXIFEN - CURRENT ISSUES AND FUTUREPROSPECTIVE

Intervention clinical trials are under way to address whether tamoxife n can prevent breast cancer development. This effort is based on labor atory evidence that tamoxifen interferes with the initiation and promo tion of mammary cancer, clinical evidence of decreased breast cancer i ncidence in the opposite breast of women participating in tamoxifen ad juvant breast cancer trials, and a favorable toxicity profile of tamox ifen providing reasonable assurance of drug safety when used in a popu lation without cancer. The apparently favorable effects of tamoxifen o n lipid metabolism and bone mineral density provide additional impetus to this evaluation. Potentially life threatening toxicity of thromboe mbolism and development of a second cancer remain concerns. With respe ct to implications of such clinical trials, even upon successful study completion, difficult issues will remain; these issues include the po tential for interaction between tamoxifen and dietary fat reduction (a lso proposed as potential breast cancer prevention), the cost and cost -effectiveness of wide scale (or selective) implementation of positive results, and the generalizability of study results to socioeconomical ly disadvantaged and racial and ethnic minority populations that histo rically have been under-represented in medical clinical trials. These important issues should be addressed concurrently as large-scale preve ntion trials go forward to optimize the practical utility of efficacy data obtained.