Overall survival beyond first-line docetaxel in patients with metastatic castrate-resistant prostate cancer treated with abiraterone acetate or enzalutamide.

e570 Background: In post-docetaxel setting of metastatic castrate-resistant prostate cancer (mCRPC), survival benefit with abiraterone acetate or enzalutamide is well established. This retrospective study was performed with the data obtained our cancer chemotherapy registry to evaluate real-world mCRPC patient outcomes. Methods: All consecutive patients treated with either abiraterone acetate or enzalutamide in post-docetaxel setting between 2013 and 2014 were included. The decision for administering second-line agents was, in most cases, at the discretion of the treating oncologists. The primary endpoint of this study was overall survival (OS), and the secondary endpoints included safety, prostate-specific antigen (PSA) response ( ≥ 50% decline) and progression-free survival (PFS). Univariate and multivariate analyses for OS were performed on the recognized baseline parameters and therapy. Results: A total of 54 eligible mCRPC patients received either abiraterone acetate (n = 25) or enzalutamide (n = 29). At the time of commencing second-line therapy, the patients’ median age was 70 years (range, 45-86) and 30 patients (56%) had a symptomatic disease. Visceral disease was present in 12 patients, and 12 had bone-only metastasis. Both were well-tolerated without significant toxicities. PSA response was observed in 36% and 52% for abiraterone acetate and enzalutamide, respectively. The estimated median PFS and OS were 5 and 15 months, respectively. Multivariate analysis revealed that the presence of clinical symptoms was the only independent prognostic factor for OS. Conclusions: Within the limitation of small sample size, the results are consistent with existing literature suggesting that both abiraterone acetate and enzalutamide appear to be effective as second-line therapy for docetaxel-pretreated mCRPC.