Enzalutamide After Docetaxel and Abiraterone Acetate Treatment in Prostate Cancer: A Pooled Analysis of 10 Case Series

Abstract

There are emerging data regarding the therapeutic benefit of enzalutamide (ENZ) in the treatment of patients with castration-resistant prostate cancer (CRPC) pretreated with docetaxel and abiraterone acetate. To systematically evaluate the evidence regarding the efficacy of ENZ after docetaxel and abiraterone acetate treatment in CRPC, we performed a pooled analysis of all available studies. Studies that enrolled CRPC patients treated with ENZ after docetaxel and abiraterone acetate treatment were identified using PubMed, Web of Science, SCOPUS, The Cochrane Register of Controlled Trials, and EMBASE. A systematic review was conducted to calculate the pooled response rate (RR) and the 95% confidence interval (CI). Pooled median progression-free survival (PFS) and overall survival (OS), weighted on the number of patients of each of the selected trials, were also calculated. We tested for significant heterogeneity using the Cochran χ2 test and the I2 index. Ten publications were selected for inclusion in this analysis. The number of included patients was 536 (range, 23-137). Overall, the pooled RR (reduction of prostate-specific antigen by > 50%) was 22.9% (95% CI, 19.3%-27.1%). The median PFS was 3.1 months (range, 1.4-4.9 months). The median OS was 8.3 months (range, 2.85-10.6 months). In patients sensitive to abiraterone, the RR to ENZ was 35% (95% CI, 27.2%-43.7%). ENZ is moderately effective in CRPC patients who were pretreated with chemotherapy and abiraterone acetate. The greater benefit is confined in patients who responded to abiraterone acetate. Further prospective evaluations of ENZ are required and the mechanisms of resistance have to be better understood.