Tamoxifen prophylaxis in breast cancer.

An increasing body of data suggests that tamoxifen can suppress development of preclinical breast cancer. Newer data in postmenopausal women also demonstrate major biologic effects of tamoxifen on risk factors for cardiovascular disease and osteoporosis. Taken together, this information supports the hypotheses that use of tamoxifen will provide overall health benefits and lower the incidence of breast cancer in selected women, particularly postmenopausal women, who are willing to take a daily hormone pill indefinitely and who do not develop significant symptomatic side effects. Clinical trials addressing these hypotheses are beginning in the United States, Great Britain, and Italy, but the design and completion of such trials present significant challenges. Until clear data are available from the clinical trials just being launched, tamoxifen should not be given to healthy women who do not have breast cancer.