Therapeutic sensitivity to standard treatments in BRCA positive metastatic castration-resistant prostate cancer patients—a systematic review and meta-analysis

Abstract

Background: Recent oncology guidelines recommend BRCA1/2 testing for a wide range of prostate cancer (PCa) patients. In addition, PARP inhibitors are available for mutation-positive metastatic castration-resistant PCa (mCRPC) patients following prior treatment with abiraterone, enzalutamide or docetaxel. However, the question of which of these standard treatments is the most effective for BRCA1/2 positive mCRPC patients remains to be answered. The aim of this meta-analysis was to assess the efficacy of abiraterone, enzalutamide and docetaxel in BRCA1/2 mutation-positive mCRPC patients in terms of PSA-response (PSA50), progression-free survival (PFS) and overall survival (OS). Methods: As no interventional trials are available on this topic, we performed the data synthesis of BRCA1/2 positive mCRPC patients by using both proportional and individual patient data. For PSA50 evaluation, we pooled event rates with 95% confidence intervals (CI), while for time-to-event (PFS, OS) analyses we used individual patient data with random effect Cox regression calculations. Results: Our meta-analysis included 16 eligible studies with 348 BRCA1/2 positive mCRPC patients. In the first treatment line, response rates for abiraterone, enzalutamide and docetaxel were 52% (CI: 25–79%), 64% (CI: 43–80%) and 55% (CI: 36–73%), respectively. Analyses of individual patient data revealed a PFS (HR: 0.47, CI: 0.26–0.83, p = 0.010) but no OS (HR: 1.41, CI: 0.82–2.42, p = 0.210) benefit for enzalutamide compared to abiraterone-treated patients. Conclusions: Our PSA50 analyses revealed that all the three first-line treatments have therapeutic effect in BRCA1/2 positive mCRPC; although, based on the results of PSA50 and PFS analyses, BRCA positive mCRPC patients might better respond to enzalutamide treatment. However, molecular marker-driven interventional studies directly comparing these agents are crucial for providing higher-level evidence.