Preventing breast cancer in high-risk women, 2008.

Several large, prospective trials have evaluated tamoxifen compared with placebo for breast cancer risk reduction in women at increased risk for breast cancer. Analysis of the large, prospective breast cancer risk-reduction trials that used tamoxifen estimated that tamoxifen decreased breast cancer incidence by 38% on average and estrogen receptor-positive tumors by 48%. Tamoxifen is known to have several serious side effects, including uterine malignancy, thromboembolic events, cataracts, and menopausal symptoms, that have limited its usefulness in the risk-reduction setting. Raloxifene (Evista) is a benzothiophene selective estrogen-receptor modulator that has antiestrogenic effects on breast and endometrial tissue as well as estrogenic effects that are similar to but distinct from tamoxifen. Among postmenopausal women who are at increased risk for breast cancer, raloxifene is as effective as tamoxifen in reducing the risk of invasive breast cancer but appears to be less effective than tamoxifen in reducing the risk of in situ breast cancer. Raloxifene causes less benign and malignant uterine changes and fewer thromboembolic events than tamoxifen. Symptomatic side effects are comparable for the two drugs. Raloxifene is more appropriate than tamoxifen for reduction of breast cancer risk among postmenopausal women at increased risk for breast cancer.