Abstract
ERA 223, a phase III, international, multicenter, double-blind study published in Lancet Oncology, was the first randomized controlled trial to investigate combined radium-223 (Ra-223) and abiraterone acetate plus prednisone or prednisolone (AAP) therapy. The data from ERA 223 demonstrated no increase in efficacy for this combination over AAP alone, and instead identified a significant safety concern due to the higher risk of fracture in the co-treatment group. The surprising results of this trial likely stem from the compounding osteoporotic effects of the different treatments, particularly the addition of prednisone, and supplementing therapy regimens with osteoprotective agents may aid in mitigating this safety risk.