Breast Cancer Prevention (PDQ®): Prevention - Health Professional Information [NCI] - Description of Evidence
An extension of the MORE study, the Continuing Outcomes Relevant to Evista (CORE) study, continued studying about 80% of MORE participants in their randomized groups for 4 years beyond the original 4 years of MORE. Although there was a median 10-month gap between the two studies and only about 55% of women were adherent to their assigned medications, the raloxifene group continued to experience a lower incidence of invasive breast cancer. As in MORE, this effect resulted from a reduction in ER–positive but not ER–negative invasive breast cancer. There was no reduction in noninvasive breast cancer. The overall reduction in invasive breast cancer during the 8 years of MORE and CORE was 66% (HR = 0.34; 95% CI, 0.22–0.50); the reduction for ER–positive invasive breast cancer was 76% (HR = 0.24; 95% CI, 0.15–0.40).
The Raloxifene Use for the Heart trial was a randomized, placebo-controlled trial to evaluate the effects of raloxifene on incidence of coronary events and invasive breast cancer. Similar to the MORE and CORE studies, raloxifene reduced the risk of invasive breast cancer (HR = 0.56; 95% CI, 0.38–0.83). The annualized rate of invasive breast cancer in the raloxifene group was 0.20% compared with 0.29% in the placebo group. Raloxifene did not reduce the risk of ER–negative breast cancer or noninvasive breast cancer. The annualized rate of noninvasive breast cancer in the raloxifene group was 0.04% compared with 0.02% in the placebo group.
STAR (NSABP P-2) compared tamoxifen and raloxifene in 19,747 high-risk women during a mean of 3.9 years of follow-up. The primary outcome measure was breast cancer incidence, which was approximately the same for invasive cancer, but favored tamoxifen for noninvasive cancer. Adverse events of uterine cancer, venous thrombolic events, and cataracts were more common in tamoxifen-treated women, and there was no difference in ischemic heart disease events, strokes, or fractures. Treatment-associated symptoms of dyspareunia, musculoskeletal problems, and weight gain favored tamoxifen, whereas vasomotor flushing, bladder control symptoms, gynecologic symptoms, and leg cramps favored raloxifene.