Efficacy and tolerability of first-line abiraterone + prednisone (ABI) versus enzalutamide (ENZ) for metastatic castration-resistant prostate cancer (mCRPC) in men ≥ 80 years: A retrospective cohort study.

5051Background: ABI and ENZ are first-line treatment options for mCRPC with comparable efficacy. In men ≥ 75 years, ABI and ENZ are associated with higher rates of adverse events. For very elderly patients (pts), the efficacy and tolerability of ABI and ENZ have not been directly compared. Methods: Retrospective analysis in pts ≥ 80 years of age who received ABI or ENZ for first-line treatment of mCRPC between July 2009 and September 2016 at the BC Cancer Agency. Medical records were reviewed for clinical characteristics and outcomes including PSA response rate (PSA50) (decrease of ≥50% from baseline), time to first progression (TTP) (PSA, radiographic or clinical progression) and overall survival (OS). Results: There were 106 pts in the ABI cohort and 104 in the ENZ cohort. Baseline characteristics were well balanced including median age 85 years (IQR 83-88); median Charlson Comorbidity Index (CCI) 7 (IQR 7-8); hemoglobin (HB) upper...