Timely germline BRCA testing after invasive breast cancer promotes contralateral risk-reducing mastectomy and improves survival: an observational retrospective study.

PURPOSE

To report the rates of risk-reducing surgery (RRS) following germline testing for BRCA1/2 (likely) pathogenic variants (BRCApv) and to assess the impact of RRS and BRCA status on survival after surgical treatment for unilateral breast cancer (BC).

METHODS

We identified 7145 women with BC (2000-2017), a BRCA test and median follow-up of 10.8 years from the Danish Breast Cancer Cooperative Group's clinical database. Distant recurrence-free (DRFS) and overall survival (OS) according to BRCA status were evaluated using the Kaplan-Meier method. Hazard ratios (HR) for BRCApv vs. BRCA wild-type, contralateral risk-reducing mastectomy (CRRM), and risk-reducing bilateral salpingo-oophorectomy (RRBSO), including interaction tests, were estimated using multivariable Cox models.

RESULTS

Among BRCA1pv carriers (n = 403), CRRM rates were higher than in BRCA2pv (n = 317) (66% vs. 52%, p < 0.001) and more likely to receive timely testing, i.e., within 6 months of BC diagnosis (75% vs. 52%, p = 0.004). Regarding RRBSO rates, no differences were observed. CRRM was associated with significantly improved DRFS (HR = 0.63, 95% CI 0.51-0.78) and OS (HR = 0.64, 95% CI 0.51-0.82), independently of BRCA status and age. RRBSO was associated with improved OS only in BRCApv carriers, specifically, those aged ≥ 50 years (HR = 0.44, 95% CI 0.26-0.75). BRCApv (irrespective of affected gene) was associated with worse DRFS (HR = 1.31, 95% CI 1.06-1.63); however, this was only evident after 2 years of follow-up (HR = 1.53, 95% CI 1.22-1.93). BRCApv was not significantly associated with worse OS (HR = 1.25, 95%CI 0.98-1.58).

CONCLUSION

Timely germline testing at BC diagnosis might increase CRRM rates in BRCApv carriers, thereby improving survival.