Influence of Germline BRCA Genotype on the Survival of Patients with Triple-Negative Breast Cancer

The presence of BRCA pathogenic variants (PV) in triple-negative breast cancer (TNBC) is associated with a distinctive genomic profile that makes the tumor particularly susceptible to DNA-damaging treatments. However, patients with BRCA PVs can develop treatment resistance through the appearance of reversion mutations and restored BRCA expression. As copy-number variants (CNV) could be less susceptible to reversion mutations than point mutations, we hypothesize that carriers of BRCA CNVs may have improved survival after treatment compared with carriers of other BRCA PVs or BRCA wild-type. Women diagnosed with stage I–III TNBC at ≤50 years at a cancer center in Mexico City were screened for BRCA PVs using a recurrent PV assay (HISPANEL; 77% sensitivity). Recurrence-free survival (RFS) and overall survival (OS) were compared according to the mutational status. Among 180 women, 17 (9%) were carriers of BRCA1 ex9–12del CNVs and 26 (14%) of other BRCA PVs. RFS at ten years for the whole cohort was 79.2% [95% confidence interval (CI), 72.3–84.6], with no significant differences according to mutational status. 10-year OS for the entire cohort was 85.3% (95% CI, 78.7–90.0), with BRCA CNV carriers demonstrating numerically superior OS rates other PV carriers and noncarriers (100% vs. 78.6% and 84.7%; log-rank P = 0.037 and P = 0.051, respectively). This study suggests that BRCA1 ex9–12del CNV carriers with TNBC may have a better OS, and supports the hypothesis that the genotype of BRCA PVs may influence survival by limiting treatment resistance mediated by reversion mutations among CNV carriers. SIGNIFICANCE: Large CNV BRCA carriers in a cohort of young Mexican patients with TNBC had superior OS rates than carriers of other BRCA pathogenic variants (i.e., small indels or point mutations). We hypothesize that this is due to the resistance of CNVs to reversion mutations mediating resistance to therapy. If validated, these findings have important prognostic and clinical treatment implications for BRCA-associated breast cancers.