Efficacy and safety of radium-223 dichloride (Ra-223) in castration-resistant prostate cancer (CRPC) patients with bone metastases who did or did not receive prior docetaxel (D) in the phase III ALSYMPCA trial.

5068 Background: Ra-223, a first-in-class α-emitter, significantly improved median overall survival (OS) by 3.6 mo vs placebo (Pbo) in CRPC patients (pts) with bone metastases (mets) receiving best standard of care (BSoC) in the ALSYMPCA study (HR = 0.695; 95% CI, 0.581-0.832; p = 0.00007), and had a highly favorable safety profile in the updated ALSYMPCA analysis (Parker et al. ASCO 2012). This predefined subgroup analysis assessed efficacy and safety of Ra-223 in pts who did or did not receive prior D (pD). Methods: Eligible pts had progressive, symptomatic CRPC with ≥ 2 bone mets; had no known visceral mets; were receiving BSoC; and had received pD, or were unfit for or declined D (npD). Pts were randomized 2:1 to 6 injections of Ra-223 (50 kBq/kg IV) q4wk or matching Pbo and stratified by prior D use, baseline alkaline phosphatase level, and current bisphosphonate use. Survival data were compared using a log-rank test. Results: 395/921 (43%) randomized pts had npD (Ra-223, n = 262; Pbo, n = 133); 526/...