Abiraterone Acetate and Enzalutamide: Similar Efficacy in Treating Post Docetaxel Metastatic Castration-resistant Prostate Cancer: Single Center Experience

Abstract

Background/Aim: Abiraterone (AA) and enzalutamide (ENZ) were introduced in Taiwan since 2012 for the treatment of patients with post-docetaxel metastatic castration-resistant prostate cancer (mCRPC). This study aims to retrospectively compare the efficacy of the two regimens. Materials and Methods: The study cohort consisted of 77 mCRPC patients previously treated with docetaxel and subsequently with AA (n=63, the AA group) or ENZ (n=13, the ENZ group), all treated in our hospital. Clinical parameters of the two groups were compared to determine differences between pre-treatment variables and treatment outcomes. Results: Sixty-four patients received AA and 13 received ENZ, with a median 18.2 vs. 14.5 months follow-up (p=0.434). Prostate-specific antigen (PSA) response >50% was 31 (48.4%) in AA and 9 (69.2%) in ENZ (p=0.171), while PSA response >90% was 16 (25%) in AA and 5 (38.5%) in ENZ (p=0.32). The median progression-free survival (PFS) was 7.3 (95%CI=4.796-9.804) months in AA and 9.5 months (95%CI=5.743-13.257) in ENZ (p of log rank=0.766). The median overall survival (OS) from second-line hormone treatment was 30.2 months in AA group and 16.2 months in ENZ group (p of log rank=0.734). Neither the uni- nor the multi-variate COX-regression analysis distinguished any advantage of the two-drug regimen in terms of PFS or OS. Metastasis volume (HR=3.032, 95%CI=1.281-7.178, p=0.012) and nadir PSA (HR=1.000, 95%CI=1.000-1.001, p=0.010) were shown as independent risk factors for the survival of AA/ENZ-treated patients. Conclusion: AA and ENZ had a similar efficacy in treating post-docetaxel mCRPC patients. Metastatic volume and nadir PSA were independent risk factors of these patients in predicting their disease-specific survival and overall survival.