On May 25, 1999. the Study of Tamoxifen and Raloxifene, or STAR, one of the largest breast cancer prevention studies ever, began recruiting volunteers at more than 400 centers across the U.S., Puerto Rico, and Canada.

The purpose of the randomized double-blinded clinical trial was to compare the effectiveness of raloxifene with that of tamoxifen in preventing breast cancer in postmenopausal women.

The trial was to include 22,000 postmenopausal women at increased risk of breast cancer to determine whether the osteoporosis prevention drug raloxifene (Evista) was as effective in reducing the chance of developing breast cancer as tamoxifen (Nolvadex) has proven to be.