The study of tamoxifen and raloxifene (STAR): Initial findings from the NSABP P-2 breast cancer prevention study
LBA5 Background: The STAR trial was designed to compare raloxifene to tamoxifen in terms of relative effect on invasive breast cancer risk and on other beneficial and detrimental outcomes associated with the use of tamoxifen. Methods: The trial opened on 7-1-1999, and accrual was completed November 4, 2004, with 19,747 women enrolled. To be eligible, a woman had to be postmenopausal with a 5-year predicted breast cancer risk of 1.66% as determined by the modified Gail model. Women were randomized and treated in a double-blinded fashion to receive 5 yr of therapy with either 20 mg per day of tamoxifen or 60 mg per day of raloxifene. The protocol-defined monitoring plan called for a final analysis and release of findings when 327 invasive breast cancer cases had been diagnosed in the total population. The mean age of the population at the time of entry into this trial was 58 yr, and the mean 5-yr risk of breast cancer was 4.04%. 93.5% of the women were white; 51.5% had a hysterectomy before entry into the study; 9.2% had a history of LCIS; 71.1% had at least one first-degree relative with a history of breast cancer. The average time on the study is 47 months. Results: There was no difference between the treatment groups in terms of effect on invasive breast cancer: 163 cases in women assigned to tamoxifen and 167 in women assigned to raloxifene (RR = 1.02, 95% CI = 0.82–1.27). The risk of invasive uterine malignancies was 40% less in the raloxifene group (36 in women assigned tamoxifen and 23 in women assigned raloxifene [RR = 0.62, 95% CI = 0.35–1.08]). The risk of non invasive breast cancer was less in the tamoxifen group (57 cases in those assigned to tamoxifen and 81 in those assigned to raloxifene [RR = 1.41, 95% CI = 1.00–2.02]). There were no significant differences between the treatment groups for any of the other invasive cancer sites or for cardiac events, osteoporotic fractures, or deaths. There were fewer thromboembolic events in women taking raloxifene than in those taking tamoxifen. Conclusions: Raloxifene is an effective alternative to tamoxifen for reducing the incidence of invasive breast cancer in postmenopausal women at increased risk of developing the disease and is associated with fewer endometrial cancers, deep vein thromboses, and pulmonary emboli. [Table: see text]