354 Background: Recent meta-analyses suggested an improvement in overall survival (OS) with the addition of Abiraterone (A) vs Docetaxel (D) to androgen deprivation therapy (ADT) in the treatment of men with metastatic castration-sensitive prostate cancer. However, none have reported castration resistance-free survival (CFS) and toxicity data; two clinically relevant outcomes for physicians and patients. Methods: We conducted a systematic review and meta-analysis to assess CFS and toxicity of adding A or D to ADT in men with castration-sensitive prostate cancer. The electronic databases Ovid MEDLINE, Cochrane Central Register of Controlled Trials and EMBASE, were searched for randomized controlled trials. Pooled hazard ratios (HR) for CFS, and pooled risk ratios (RR) for grade 3 or higher toxicity were analyzed using the Mantel-Haenszel method and generic inverse variance. To account for between-studies heterogeneity, random-effect models were used to compute pooled estimates. Subgroup analyses compared patients on A and D in terms of CFS. Results: Five studies were included. The addition of A or D to ADT decreased the risk of development of castration-resistance by 53% (5 studies, 4,462 participants, HR = 0.47, 95% CI 0.33-0.67). In a subgroup analysis, the addition of A seemed to be better than D for the outcome CFS (5 studies, HR = 0.31, 95% CI 0.27-0.34 versus HR = 0.62, 95% CI 0.56-0.69, test for subgroup difference, p< 0.001). Different profiles of toxicity were seen with A and D. While A increased the risk of hypokalemia (3,107 participants, HR = 6.63, 95% CI 3.5-12.5) and cardiac toxicity (3,107 participants, HR = 2.4, 95% CI 1.7-3.3), D increased the risk of neutropenia (2,151 participants, HR = 13, 95% CI 8.9-18.8) and neuropathy (2,151 participants, HR = 2.25, 95% CI 1.18-4.3). Conclusions: The addition of A and D to ADT increases CFS in men with castration-sensitive prostate cancer, with a longer CFS noted for A compared to D. Considering CFS and OS, A may be preferred to D as initial therapy. Toxicity profiles differed between A and D. Quality of life and cost differences between A and D are other important factors and were not considered in this analysis.