Contralateral risk-reducing local therapy in breast cancer patients with BRCA1/2 mutations: systemic review and meta-analysis

Background: Unilateral breast cancer (UBC) patients with germline pathogenic BRCA1/2 variants have a higher risk of developing contralateral breast cancer (CBC) and need contralateral risk-reducing local treatments, including contralateral risk-reducing mastectomy (CRRM) and prophylactic irradiation (CPI). The aim of our study was to systematically explore the efficacy of CRRM and CPI in reducing CBC risk and increasing survival.

Methods: A search was done, and eligible randomized trials and cohort studies should include and compare UBC patients with germline pathogenic BRCA1/2 variants who have and have not received contralateral risk-reducing local treatment. Random-effects meta-analysis was used in this study. Primary outcomes of the studies included overall survival (OS) and the incidence of contralateral breast cancer (CBC), and secondary outcomes included breast cancer-specific survival (BCSS).

Results: A total of five studies with 1769 UBC patients with germline pathogenic BRCA1/2 variants were enrolled in our meta-analysis. CRRM was correlated with a lower risk of CBC in UBC patients with germline pathogenic BRCA1/2 variants (summary RR = 0.07; 95%CI 0.03-0.13, I² = 3%), a significantly increased OS (summary RR, 1.15; 95%CI 1.04-1.26, I² = 26%) and a significantly increased BCSS (summary RR, 1.18; 95%CI 1.07-1.31, I² = 64%) compared with surveillance. CPI also decreased the risk of CBC (RR 0.02; 95%CI 0.05-0.88) but did not significantly improve OS (RR 0.97; 95%CI 0.90-1.05) and BCSS (RR 0.97; 95%CI 0.90-1.05) compared with surveillance.

Conclusions: CRRM reduces CBC risk and increases OS and BCSS in UBC patients with germline pathogenic BRCA1/2 variants, and could be offered as a risk-reducing local treatment. For those who oppose CRRM, CPI could be offered for CBC-risk reduction, while its survival benefit is still uncertain.