Background: Ra-223 is a first-in-class alpha-emitting pharmaceutical recently Food and Drug Administration approved for treatment (tx) of patients (pts) with CRPC and symptomatic bone metastases (mets). In ALSYMPCA, Ra-223 significantly improved overall survival by 3.6 months versus placebo (pbo) (HR = 0.70; 95% CI, 0.58-0.83; P < 0.001) and was well tolerated. Reported here are long-term safety data ~1.5 years after the last pt’s final injection (inj) from the entire ALSYMPCA safety population. Methods: Eligible pts had progressive CRPC with ≥ 2 symptomatic bone mets and no known visceral mets, were receiving best standard of care, and had received docetaxel or were unfit for or declined docetaxel. Pts were randomized 2:1 to 6 inj of Ra-223 (50 kBq/kg IV; q 4 wk) or matching pbo. Only adverse events (AEs) considered tx related by the investigator were reported during follow-up. Long-term safety data were assessed by specific diseases, including acute myelogenous leukemia, myelodysplastic syndrome, aplastic anemia, primary bone cancer, or primary cancer in other organs. Results: ALSYMPCA safety population included 901 pts (Ra-223, n = 600; pbo, n = 301). Overall, 25 (4%) Ra-223 and 8 (3%) pbo pts had ≥ 1 tx-related AE (Table). During follow-up, primary cancer in other organs was reported in 5 pts (Ra-223, n = 2; pbo, n = 3). Conclusions: Ra-223 is an effective and well-tolerated tx for CRPC with symptomatic bone mets. No major safety issues were identified within ~1.5 years after tx in the ALSYMPCA safety population. Clinical trial information: NCT00699751.

* Grade 5.