Radium-223 therapy for metastatic castration-resistant prostate cancer: survival benefit when used earlier in the treatment pathway

Background Radium-223 dichloride (Ra-223) therapy improves overall survival in bony metastatic castration-resistant prostate cancer (mCRPC) patients. Recent guidance change recommends Ra-223 following at least two prior therapies for mCRPC. We evaluated how this change affects overall survival and the optimal timing of Ra-223 in the mCRPC treatment pathway. Methods Retrospective analysis of all mCRPC patients receiving Ra-223 therapy at a single UK centre over a 70-month period. Overall survival, number of prior lines of therapy commenced before Ra-223 initiation and number of Ra-223 therapy cycles completed were identified. Results One hundred ninety-one mCRPC patients received Ra-223 therapy during the study period. One hundred twenty-one (63%) received one prior therapy (group 1) and 70 (37%) received two prior therapies (group 2). Median survival in group 1 was significantly improved, compared to group 2 (448 days vs. 341 days (P = 0.03). Subgroup analysis of 111/191 (58%) patients that completed the recommended six Ra-223 therapy cycles showed additional improved survival. Median survival in group 1 was incrementally significantly improved, compared to group 2 within these patients (665 days vs. 552 days; P = 0.05). There was no difference in the number of patients completing the recommenced six cycles of therapy between the groups [72/121 (59%) vs. 39/70 (56%); P = 0.61]. Conclusion We found a significant survival benefit when Ra-223 was used earlier in the mCRPC treatment pathway, with additional survival advantage seen in those patients completing all six Ra-223 cycles. Our results support the use of Ra-223 earlier in the treatment pathway.