ENDOCRINE PREVENTION OF BREAST CANCER

During the past four decades, the prospects of developing medicines to reduce the risk of breast cancer in healthy women have gone from a laboratory concept to a clinical reality. Tamoxifen, the pioneering selective estrogen receptor modulator (SERM), was initially shown to prevent rodent mammary carcinogenesis and the data were used to suggest prospective placebo-controlled clinical trials. Tamoxifen reduced the incidence of breast cancer by 50%; but, most importantly, this reduction versus placebo was maintained for a decade after stopping the drug. A small but significant increase in endometrial cancer in postmenopausal women taking tamoxifen, but not premenopausal women, makes tamoxifen the chemopreventive of choice for the high risk premenopausal woman. The finding that the SERM raloxifene maintains bone density in postmenopausal women but decreases breast cancer incidence without an increase in endometrial cancer makes raloxifene the chemopreventive of choice in postmenopausal women. A range of new and novel SERMs has completed clinical testing.