Breast cancer prevention trials.

A new option for women at increased risk for breast cancer is chemoprevention--namely, an attempt to decrease breast cancer incidence by means of drug therapy. The efficacy of tamoxifen as a chemopreventive agent has been studied to date in three randomized, controlled trials, with varying results. Investigators with the National Surgical Adjuvant Breast and Bowel Project (NSABP) Breast Cancer Prevention Trial found that tamoxifen reduced the incidence of breast cancer by almost half, whereas British and Italian researchers found no significant benefit. This disparity is due, in part, to differences in the baseline breast cancer risk characteristics among the study populations, differing cohort sizes, variable use of hormone replacement therapy, and other factors. In this article, we review the eligibility criteria, treatment plans, and results from the three published randomized trials of tamoxifen versus placebo. We also review the data on raloxifene and breast cancer incidence. Chemoprevention with tamoxifen, in a non-study setting, is one option for women at increased risk for breast cancer. The ongoing Study of Tamoxifen and Raloxifene (STAR) is a randomized, double-blinded trial comparing the effectiveness of raloxifene with that of tamoxifen in postmenopausal women at increased risk for developing breast cancer. Until the results of this trial are available, it is premature to use raloxifene for primary breast cancer prevention.