Tamoxifen and risk of contralateral breast cancer among women with inherited mutations in BRCA1 and BRCA2: a meta-analysis

Given the greatly elevated risks of contralateral breast cancer (CBC) observed in breast cancer patients who carry mutation in BRCA1 or BRCA2, the present meta-analysis was addressed to determine whether adjuvant tamoxifen treatment for breast cancer is associated with reduced CBC risk for these patients. We searched the database of PubMed for eligible studies about the effectiveness of tamoxifen on CBC risk among BRCA1/2 mutation carriers, and we calculated the pooled relative risks (RRs) for CBC risk along with 95 % confidence intervals (CIs). Fixed- or random-effects model was conducted according to study heterogeneity. Four non-overlapping studies met the inclusion criteria for the meta-analysis. Tamoxifen was found to be significantly associated with reduced risk of CBC among BRCA1/2 mutation carriers (summary RR = 0.56, 95 % CI = 0.41–0.76). Similar findings were observed in BRCA1 mutation carriers (summary RR = 0.47, 95 % CI = 0.37–0.60) and BRCA2 mutation carriers (summary RR = 0.39, 95 % CI = 0.28–0.54), respectively. In conclusion, tamoxifen significantly reduces the incidence of CBC among BRCA1/2 mutation carriers with primary unilateral breast cancer. It can reasonably be offered to breast cancer patients with BRCA1 or BRCA2 mutation for the prevention of CBC. Further studies are required to get a more precise estimation of the benefits and harms of tamoxifen in these patients.