Outcomes in patients (Pts) with advanced prostate cancer and inactivating germline mutations in BRCA2 or ATM.

Abstract

242 Background: Germline mutations in homologous recombination repair (HRR) genes, including BRCA2, are present in 6-12% of pts with metastatic castration-resistant prostate cancer (mCRPC). BRCA2 germline mutations are associated with high-grade and poor-prognosis localized disease, while outcomes in pts with advanced prostate cancer continue to be defined. Methods: Germline DNA from 536 consecutive mCRPC pts in our liquid biopsy program were screened for BRCA2 and ATM gene mutations using targeted sequencing. Kaplan-Meier curves were used to estimate the median time from androgen deprivation therapy (ADT) initiation to mCRPC, progression free survival (PFS) on first-line androgen receptor (AR) targeted therapy, and overall survival (OS). Outcomes in BRCA2 or ATM germline mutation carriers and a subset of the total sample of HRR wild-type (WT) pts, who had clinical data available (n = 113), were compared using the log-rank test. Results: 26/536 (4.9%) of pts had germline BRCA2 (n = 22) or ATM mutations (n = 4). After ADT initiation, HRR mutated pts progressed to mCRPC with a median time of 13.4 mo compared to 19.0 mo in WT pts (HR = 1.6, [95% CI 1.0-2.5], p = 0.03). HRR mutated pts had a median PFS on first-line AR-targeted therapy in the mCRPC setting of 3.3 mo versus 7.9 mo in WT pts (HR = 2.2, [95% CI 1.3-3.5], p = 0.002). OS for HRR mutated pts from the time of ADT was 57.7 mo in contrast to 104.9 mo in WT pts (HR = 1.8, [95% CI 1.0-3.4], p = 0.07). OS from time of CRPC was 29.7 mo in HRR mutated pts versus 50.3 mo in WT pts (1.6, [95% CI 0.8-2.9], p = 0.16). Conclusions: Germline HRR mutated pts perform poorly with shorter PFS on first-line AR-targeted therapy and time to mCRPC, in contrast to WT pts. These findings support the hypothesis that BRCA2 and ATM gene mutated pts have poor outcomes with current AR-targeted treatments and should be evaluated for alternate regimens.