Two-Year Survival Follow-Up of the Randomized, Double-Blind, Placebo-Controlled Phase II Study of Radium-223 Chloride in Patients With Castration-Resistant Prostate Cancer and Bone Metastases

In this 24-month follow-up of a phase II study in patients with castration-resistant prostate cancer (CRPC) and bone metastases, radium-223 (4 injections of 50 kBq/kg every 4 weeks [n = 33]) improved median overall survival vs. matching placebo (n = 31) (65.3 vs. 46.4 weeks, respectively; log-rank P = .056), with no long-term safety concerns. Data suggest that treatment of bone disease with radium-223 has survival benefits. Background: This phase II randomized, placebo-controlled study was conducted to evaluate efficacy and safety of radium-223 in patients with castration-resistant prostate cancer (CRPC) and painful bone metastases. Twelve-and 18-month survival results were reported previously. Here we report 24-month overall survival (OS) and safety data from the period 12 to 24 months after the first injection of study medication. Methods: Patients with CRPC and bone pain were randomized 1: 1 to receive 4 injections of radium-223 (50 kBq/kg [n = 33]) or placebo (n = 31) after external-beam radiotherapy; each injection was given every 4 weeks. Endpoints for this report were 24-month OS, long-term safety, and treatment-related adverse events (AEs) occurring in the 12- to 24-month period. Results: After 24 months, 10 (30%) patients were alive in the radium-223 group compared with 4 patients (13%) in the placebo group. Patients who received at least 1 dose of study medication had a median OS of 65 weeks in the radium-223 group vs. 46 weeks in the placebo group (log-rank P = .056). The hazard ratio (HR) for OS, adjusted for baseline covariates, was 0.476 (95% confidence interval [CI], 0.258-0.877; Cox regression P = .017). The most frequent cause of death for both arms was disease progression. There were no reports of treatment-related AEs or long-term hematologic toxicity during the 12- to 24-month follow-up. Conclusion: Radium-223 had a highly favorable safety profile, with no evidence of second malignancies at 24-month follow-up. The significant improvement in OS observed in patients receiving radium-223 vs. placebo suggests that treatment of bone disease with radium-223 has survival benefits. Clinical Genitourinary Cancer, Vol. 11, No. 1, 20-6 (C) 2013 Elsevier Inc. All rights reserved.