Bone‐modifying agents are protective for symptomatic skeletal events in Radium‐223 treatment

Abstract

IntroductionRadium‐223 (Ra‐223) dichloride therapy increases overall survival and delays time to the first symptomatic skeletal event (SSE) in patients with castration‐resistant prostate cancer (CRPC) and bone metastases. Bone‐modifying agents (BMA) reduce SSE in patients with bone metastasis, but there is little information on their use with Ra‐223. This study aimed to investigate the effect of BMA on SSE in patients with bone metastatic CRPC treated with Ra‐223 in real‐world practice.MethodsWe included 73 patients treated with Ra‐223 from 10 institutions in Japan. Time to the first SSE was estimated using the Kaplan–Meier method and compared between groups using the log‐rank test. We used univariate analysis to ascertain the association between variables and SSE.ResultsDuring a median follow‐up of 12.7 months (interquartile range, 7–21.7), 12 (16.4%) patients presented SSE. Age and BMA use were different between men with and without SSE. The 1‐year SSE‐free survival rate from Ra‐223 treatment initiation was 82.4% (95% CI, 69.4%–90.2%). BMA use was associated with favorable SSE‐free survival (hazard risk, 0.23; 95% confidence interval, 0.061–0.85; p = 0.027). Two (4.7%) and seven (23.3%) patients presented symptomatic pathological bone fracture in groups with and without BMA use, respectively (p = 0.017).ConclusionThis study stresses the importance of BMA use in patients with CRPC and bone metastases in Ra‐223 treatment.