Prognosis and safety of radium-223 with concurrent abiraterone acetate or enzalutamide use for metastatic castration-resistant prostate cancer: Real-world data of Japanese patients

ObjectivesTo evaluate the real-world data on the efficacy and safety of a combination therapy with radium-223 (Ra-223) and second-generation androgen-receptor targeting agents (ARTAs), including abiraterone acetate (ABI) and enzalutamide (ENZ), among Japanese patients with bone metastatic castration-resistant prostate cancer (CRPC).Patients and methodsWe retrospectively reviewed 79 patients with bone metastatic CRPC who were treated with Ra-223. The number of patients with concurrent ARTA use was 24:17 receiving ABI and 7 receiving ENZ. We evaluated the overall survival (OS) according to ARTA use and compared the survival of patients treated with Ra-223 with or without ARTA using multivariate analysis.ResultsThe median survival in the entire cohort was 23.5 months. The patients receiving Ra-223 combined with ARTA showed a tendency of better OS than patients treated with Ra-223 alone, although no significant difference was observed (median OS, 26.5 vs 23.5 months; P = .115). A multivariate analysis showed that the extent of disease on bone scan (EOD) scores and pain at baseline were significant predictors of OS. The concurrent use of bone-modifying agents (BMAs) was not significant for favorable OS (P = .050). However, the concurrent use of second-generation ARTA was not a significant factor for OS. Regarding safety, a bone fracture occurred in only one (4.2%) of 24 patients treated with combined Ra-223 and ARTA therapy.ConclusionOur real-world data analysis suggested that Ra-223 combined with a second-generation ARTA is well tolerated in Japanese patients. The EOD score and pain at baseline are significant prognostic factors for OS, but the concurrent use of second-generation ARTA has no influence on OS among men treated with Ra-223. The concurrent use of BMA yields a marginally favorable OS.