The FDA approved radium Ra 223 dichloride (Xofigo Injection, Bayer HealthCare Pharmaceuticals) for the treatment of patients with castration-resistant prostate cancer, symptomatic bone metastases and no known visceral metastatic disease.  

The alpha-particle emitting radiotherapy mimics calcium and forms complexes with hydroxyapatite at bone metastases.

The FDA based its approval on a double-blind, randomized, placebo-controlled trial in patients with metastatic castration-resistant prostate cancer with symptomatic bone metastases and no known visceral metastatic disease. The primary endpoint of the study was overall survival.

A total of 541 patients were treated with Xofigo plus best standard of care; another 268 were allocated to matching placebo plus best standard of care. “Best standard of care included local radiotherapy, corticosteroids, anti-androgens, estrogens, estramustine or ketoconazole,” the FDA explained in a release. All patients were to continue androgen deprivation therapy.  

At interim analysis, median overall survival in the Xofigo arm showed a statistically significant improvement at 14 months vs. 11.2 months in the placebo arm. The Xofigo cohort also demonstrated a delay in time-to-first symptomatic skeletal event compared with the placebo arm.