BRCA1 and breast cancer: According to a meta-analysis, treatment with tamoxifen for a first breast cancer reduced the risk of a second breast cancer in BRCA1 and BRCA2 germline variant carriers by 44% (HR 0.56; 95% CI 0.41–0.76), 0.47 (95% CI 0.37–0.60) for BRCA1 and 0.39 (95% CI 0.28–0.54) for BRCA2 germline variant carriers [68].