New results from an early-access, phase 3b trial of radium-223 dichloride (223Ra) in men with metastatic castration-resistant prostate cancer (mCRPC) corroborate survival and safety data of the ALSYMPCA trial. Furthermore, the data show that 223Ra treatment is safe in patients who also receive abiraterone and/or enzalutamide.

This new trial was initiated to give men with mCPRC access to 223Ra treatment ahead of regulatory approval. In contrast to the ALSYMPCA trial, which investigated efficacy outcomes of 223Ra in patients with mCRPC and symptomatic skeletal metastases, this study also included men with asymptomatic skeletal metastases and those who had received or commenced treatment with abiraterone, enzalutamide or denosumab.

In total, 696 patients enrolled in 14 countries received at least one of six planned 223Ra injections. At baseline, 20% of these men were asymptomatic, 60% had received docetaxel and 48% had received abiraterone and/or enzalutamide. All six 223Ra treatments were administered in 58% of patients.

At a median follow-up duration of 7.5 months, median overall survival was 16 months. Post hoc analyses showed longer overall survival in men who received abiraterone and/or enzalutamide or denosumab concomitantly with 223Ra compared with those who received 223Ra only. No difference in survival was seen for previous docetaxel use. Overall, adverse event profiles were similar to those in the ALSYMPCA trial. In addition, the data did not show worse safety profiles in men receiving abiraterone, enzalutamide or denosumab concomitantly to 223Ra.

This study was not randomized and had a short follow-up period. Randomized trials to investigate combination therapies of 223Ra and abiraterone or enzalutamide are currently ongoing.