Breast Cancer Risk and Breast-Cancer-Specific Mortality following Risk-Reducing Salpingo-Oophorectomy in BRCA Carriers: A Systematic Review and Meta-Analysis

SIMPLE SUMMARY: Women with BRCA1 or BRCA2 gene mutations are at increased risk of breast and ovarian cancer and often undergo operations to remove both their ovaries in order to prevent ovarian cancer. The impact of this operation on breast cancer risk is uncertain; thus, we performed a systematic review and meta-analysis to determine it. We found that this operation was not linked with a reduced risk of developing breast cancer when considering both BRCA1 and BRCA2 carriers together but was linked with a reduced risk of breast cancer when considering BRCA2 carriers alone. If a woman had this operation after developing breast cancer, it was not related to a reduced chance of developing cancer in the other breast. However, it was associated with increased survival following breast cancer when considering BRCA1 and BRCA2 carriers together and BRCA1 carriers alone. These findings may have important implications for counselling for women in the clinic. ABSTRACT: Background: Risk-reducing salpingo-oophorectomy (RRSO) is the gold standard method of ovarian cancer risk reduction, but the data are conflicting regarding the impact on breast cancer (BC) outcomes. This study aimed to quantify BC risk/mortality in BRCA1/BRCA2 carriers after RRSO. Methods: We conducted a systematic review (CRD42018077613) of BRCA1/BRCA2 carriers undergoing RRSO, with the outcomes including primary BC (PBC), contralateral BC (CBC) and BC-specific mortality (BCSM) using a fixed-effects meta-analysis, with subgroup analyses stratified by mutation and menopause status. Results: RRSO was not associated with a significant reduction in the PBC risk (RR = 0.84, 95%CI: 0.59–1.21) or CBC risk (RR = 0.95, 95%CI: 0.65–1.39) in BRCA1 and BRCA2 carriers combined but was associated with reduced BC-specific mortality in BC-affected BRCA1 and BRCA2 carriers combined (RR = 0.26, 95%CI: 0.18–0.39). Subgroup analyses showed that RRSO was not associated with a reduction in the PBC risk (RR = 0.89, 95%CI: 0.68–1.17) or CBC risk (RR = 0.85, 95%CI: 0.59–1.24) in BRCA1 carriers nor a reduction in the CBC risk in BRCA2 carriers (RR = 0.35, 95%CI: 0.07–1.74) but was associated with a reduction in the PBC risk in BRCA2 carriers (RR = 0.63, 95%CI: 0.41–0.97) and BCSM in BC-affected BRCA1 carriers (RR = 0.46, 95%CI: 0.30–0.70). The mean NNT = 20.6 RRSOs to prevent one PBC death in BRCA2 carriers, while 5.6 and 14.2 RRSOs may prevent one BC death in BC-affected BRCA1 and BRCA2 carriers combined and BRCA1 carriers, respectively. Conclusions: RRSO was not associated with PBC or CBC risk reduction in BRCA1 and BRCA2 carriers combined but was associated with improved BC survival in BC-affected BRCA1 and BRCA2 carriers combined and BRCA1 carriers and a reduced PBC risk in BRCA2 carriers.