Survival outcomes in BRCA1 or BRCA2 mutation carriers and the influence of triple-negative breast cancer subtype

Abstract

Context: Little information exists on whether breast cancer survival differs by BRCA1 or BRCA2 mutation.
Objective: To determine if the risk of subsequent breast cancer or mortality differs by BRCA1 vs BRCA2 mutation status in women with hereditary breast cancer and whether these outcomes are modified by triple-negative biologic subtype.
Design: Retrospective cohort of 307 women with breast cancer diagnosed between 1990 and 2012 who were BRCA1 or BRCA2 mutation carriers identified from a managed care organization. Subjects were followed-up through 2013.
Main Outcome Measures: Subsequent breast cancer or death.
Results: In the cohort, 163 (53.0%) were BRCA1 mutation carriers, 142 (46.3%) were BRCA2 mutation carriers, and 2 (0.7%) had mutations in both genes. Median follow-up was 4.5 years (maximum = 24 years). The percentage of subsequent breast cancer events was similar, with 17.8% in BRCA1 and 15.3% in BRCA2 mutation carriers. Overall 5-year survival was similarly high, with 91.4% for BRCA1 and 94.4% for BRCA2 mutation carriers. In a subset of 215 BRCA mutation carriers, triple-negative breast cancer (TNBC) was associated with greater mortality (adjusted hazard ratio = 1.41, 95% confidence interval = 0.40-5.05) and higher risk of subsequent breast cancer (adjusted hazard ratio = 1.65, 95% confidence interval = 0.63-4.31) than non-TNBC (reference), but the confidence intervals included the null given the small sample.
Conclusion: The TNBC status was independently associated with worse outcomes regardless of BRCA1 or BRCA2 mutation status, suggesting that targeting treatment for TNBC may enhance survival. These results require confirmation in larger studies.