In 1999, Siteman Cancer Center investigators joined the STAR (Study of Tamoxifen and Raloxifene) trial for breast cancer prevention, one of the largest in the U.S. Women at increased risk of developing breast cancer, who had gone through menopause, and were at least 35 years old took part in STAR. STAR began enrolling participants in 1999. Enrollment was closed on November 4, 2004, with 19,747 women recruited.

STAR researchers used the Breast Cancer Risk Assessment Tool, developed by scientists at NCI and NSABP, to estimate a woman’s risk of breast cancer using most of the above factors. In addition, for STAR, women diagnosed as having lobular carcinoma in situ (LCIS), a condition that is not cancer but indicates an increased chance of developing invasive breast cancer, were eligible based on that diagnosis alone, as long as their treatment for the condition was limited to local excision.

Tamoxifen is a drug, taken by mouth as a pill. It has been used for more than 30 years to treat patients with breast cancer. Tamoxifen works against breast cancer, in part, by interfering with the activity of estrogen, a female hormone that promotes the growth of breast cancer cells. In October 1998, the U.S. Food and Drug Administration (FDA) approved the use of tamoxifen to reduce the incidence of breast cancer in women at increased risk of the disease based on the results of the NSABP Breast Cancer Prevention Trial (BCPT).