The Study: To be fair, there’s been a lot of competition in that arena lately. Currently, there is a category 1 recommendation for its use in men with metastatic castration-resistant prostate cancer (mCRPC) with bone mets but without visceral mets while on androgen deprivation therapy (ADT) following external beam radiation to painful sites of disease. Whew. But even with all of these caveats, there’s still a lot of men out there who fit this bill. The problem is that Ra-223 is mutually exclusive with another category 1 recommendation for docetaxel in this population, and it has an unclear role in the setting of the final category 1 recommendations of abiraterone or enzalutamide. Enter the Bayer-funded phase 3 ERA 223 trial that randomized 806 such men receiving daily abiraterone to +/- Ra-223 q4 weeks x 6. Of note, all enrollees were both chemo-naive and asymptomatic. Unfortunately the primary endpoint of median survival free from symptomatic skeletal events was actually worse with Ra-223 (22 months) than without (26 months). This could be because it doubled rates of fracture from 11% to 29%.
Bottom Line: In the era of docetaxel and abiraterone, Ra-223 is left without a clear role in the treatment of metastatic prostate cancer. | Smith, Lancet Oncol 2019