Olaparib for the Treatment of Patients With Metastatic Castration-Resistant Prostate Cancer and Alterations in BRCA1 and/or BRCA2 in the PROfound Trial

PURPOSE Phase III PROfound trial (ClinicalTrials.gov identifier: NCT02987543) met its primary and key secondary objectives, demonstrating significantly longer radiographic progression-free survival (rPFS) and overall survival (OS) with olaparib monotherapy versus abiraterone or enzalutamide (control) in patients with metastatic castration-resistant prostate cancer (mCRPC) with alterations in BRCA1, BRCA2 (BRCA), and/or ATM (cohort A) whose disease had progressed on prior next-generation hormonal agent (NHA). We report exploratory post hoc analysis of the subgroup of patients with mCRPC with BRCA alterations in PROfound. METHODS All patients had an alteration in a homologous recombination repair gene by tumor tissue testing, of which 160 had underlying BRCA alterations. rPFS and OS were estimated using the Kaplan-Meier method. Confirmed objective response rate and safety were also assessed. RESULTS Olaparib was associated with longer rPFS (hazard ratio [HR], 0.22 [95% CI, 0.15 to 0.32]) and OS (HR, 0.63 [95% CI, 0.42 to 0.95]) than control. There was an rPFS benefit with olaparib in all zygosity subgroups (biallelic [n = 88]; HR, 0.08 [95% CI, 0.04 to 0.16], heterozygous [n = 15] and unknown [n = 57]; HR, 0.30 [95% CI, 0.16 to 0.60]). Patients with BRCA2 homozygous deletions experienced prolonged responses to olaparib (n = 16; median rPFS, 16.6 months [95% CI, 9.3 to not reached]). Some evaluations are limited by small patient numbers. Germline DNA analysis was performed for 112 (70%) patients; risk of disease progression was similar for patients with germline (n = 61; HR, 0.08 [95% CI, 0.03 to 0.18]) and somatic (n = 51; HR, 0.16 [95% CI, 0.07 to 0.37]) BRCA alterations. CONCLUSION In all subgroups assessed, olaparib improved outcomes versus abiraterone or enzalutamide for patients with mCRPC with BRCA alterations whose disease had progressed on previous NHA.