Effects of Tamoxifen vs Raloxifene on the Risk of Developing Invasive Breast Cancer and Other Disease Outcomes. The NSABP Study of Tamoxifen and Raloxifene (STAR) P-2 Trial

Abstract

The selective estrogen receptor modulator (SERM) tamoxifen has long been used to treat both early and advanced breast cancer. Raloxifene is a second-generation SERM that, in addition to combatting osteoporosis, may also lessen the risk of invasive breast cancer in postmenopausal women; The National Surgical Adjuvant Breast and Bowel Project (NSABP) Study of Tamoxifen and Raloxifene (STAR) is a prospective, randomized, double-blind trial conducted at nearly 200 clinical centers throughout North America. Participating were 19,747 postmenopausal women whose mean age was 58.5 years and whose 5-year breast cancer risk was increased at 4.03%. The minimal 5-year risk for entering the trial was 1.66%. The women received either 20 mg tamoxifen or 60 mg raloxifene daily for 5 years. During a mean follow up of 3.9 years, there were 163 cases of invasive breast cancer in women assigned to receive tamoxifen and 268 in those assigned to raloxifene, for respective incidence rates of 4.3 and 4.4 per 1000 and a risk ratio (RR) of 1.02 (95% confidence interval [CI], 0.82-1.28). Noninvasive breast cancers were less numerous in the tamoxifen group (RR, 1.40; 95% CI, 0.98-2.00), but uterine cancers were more frequent in this group (RR, 0.62; 95% CI, 0.35-1.08). No group differences were documented for invasive cancer at other sites, ischemic heart disease events, or strokes. Thromboembolic events were less frequent in raloxifene-treated women. Women in the 2 treatment groups had similar numbers of osteoporotic fractures. Those taking raloxifene had fewer cataracts and underwent fewer cataract surgeries. There was no difference in total deaths, and causes of death were similarly distributed in the 2 groups.