Impact of homologous recombination repair/BReast CAncer (BRCA) gene alterations on survival in a real‐world setting of metastatic prostate cancer

Abstract

ObjectiveTo investigate alterations of homologous recombination repair (HRR) and especially BReast CAncer 1/2 (BRCA1/2) gene on overall survival (OS). Moreover, to explore the effect of inhibition of poly(ADP‐ribose)‐polymerase (PARPi) as systemic therapy for metastatic castration‐resistant prostate cancer (mCRPC).Patients and methodsOf all HRR‐screened patients with metastatic prostate cancer, baseline characteristics were sampled. Kaplan–Meier estimates and multivariable Cox regression models predicted the effect of HRR/BRCA1/2 alterations on OS.ResultsOf 196 eligible patients, 61 (31%) harboured any HRR and 40 (20%) BRCA1/2 alterations. Of HRR alterations, 40 (66%) vs six (10%) vs five (8.2%) vs four (6.6%) vs two (3.3%) vs four (6.6%) were BRCA1/2 vs Ataxia‐telangiectasia mutated kinase (ATM) vs checkpoint kinase 2 (CHEK2) vs cyclin‐dependent kinase 12 (CDK12) vs Fanconi anaemia complementation Group A (FANCA) vs positive for other mutations. Of these, 30% received a PARPi. OS differed significantly between HRR‐positive vs ‐negative patients. Specifically in hormone‐sensitive prostate cancer, the median OS was 63 (HRR positive) vs 57 (BRCA1/2 positive) vs 113 months (HRR negative) (P ≤ 0.01). In mCRPC, OS was 42 (HRR positive) vs 41 (BRCA1/2 positive) vs 70 months (HRR negative) (P ≤ 0.01). HRR and BRCA1/2 alterations were associated with worse OS after multivariable adjustment. Finally, patients with mCRPC with BRCA1/2 mutation treated without PARPi harboured worse OS than patients with BRCA1/2 mutation and PARPi therapy (median OS: 33 vs 48 months, P < 0.03).ConclusionIncidence of HRR alteration in a clinical real‐world setting is high when using blood‐ and tissue‐based tests. Patients with HRR/BRCA alterations have worse outcomes resulting in significant OS differences between HRR/BRCA‐positive patients with mCRPC with and without PARPi usage vs HRR/BRCA‐negative patients.