Radium‐223 plus Enzalutamide Versus Enzalutamide in Metastatic Castration‐Refractory Prostate Cancer: Final Safety and Efficacy Results

Lessons Learned Long‐term safety of radium‐223 with enzalutamide was confirmed in this clinical trial. PSA‐PFS2 was prolonged with the combination compared with enzalutamide alone. Background Previously, we showed the combination of radium‐223 and enzalutamide to be safe and associated with improved efficacy based on a concomitant decline in serum bone metabolism markers compared with enzalutamide alone in a phase II trial of men with metastatic castration‐resistant prostate cancer (mCRPC) [1]. Methods Secondary endpoints were not included in our initial report, and we include them herein, after a median follow‐up of 22 months. These objectives included long‐term safety, prostate‐specific antigen (PSA)–progression‐free survival (PFS), and radiographic progression‐free survival; PSA‐PFS2 (time from start of protocol therapy to PSA progression on subsequent therapy); time to next therapy (TTNT); and overall survival (OS). Survival analysis and log‐rank tests were performed using the R statistical package v.4.0.2 (https://www.r-project.org). Statistical significance was defined as p