Radium-223 treatment patterns in a large real-world population.

Abstract

190 Background: For men with symptomatic metastatic castration resistant prostate cancer (mCRPC), radium-223 was shown to improve overall survival in the phase III, double blind ALSYMPCA trial. Despite the observed benefits, the application and practice patterns of Radium-223 outside of clinical trials are largely unknown. Here we aim to better characterize the use of radium-223 in a large and heterogeneous real-world population. We identify treatment patterns associated with radium-223 and link these patterns with time to skeletal related event (SRE) and mortality. Methods: We reviewed charts of all men with diagnosed with mCRPC in the entire Veterans Affairs (VA) system alive as of January 1, 2013 who received radiun-223. We generated Kaplan Meier curves for survival and time to SRE based on treatment patterns. We examined the association between common treatment patterns and mortality and time to SRE with Cox models. Results: We identified 318 men with bone mCRPC who received radium-223. Median age at radium start was 69 ys and median follow up was 25.3 months. Median survival was 11 months. 277 patients died during the study period (87%). 50% (158/318) completed ≤4 injections. There was a significant difference mortality among four consolidated treatment patterns (p=0.005) and but no difference SRE (p=0.10). On univariable and multivariable analysis, men who received AR target + docetaxel + radium-223 had increased mortality vs. men who received AR target + radium-223 (p=0.010 and 0.005, respectively). Multivariable analysis showed that non-black race, bone pain, SRE prior to radium, and higher PSA were all linked with worse mortality. Conclusions: We described the largest known cohort of men in the real world who received radium-223. We identified common treatment patterns with differing risk for overall mortality. Further prospective studies are needed to better understand whether differences in survival are attributed to worsening disease status requiring more aggressive therapy, lead-time bias, or true differences in treatment efficacy.