Radium-223 Dichloride, otherwise known as Xofigo, is the first alpha-emitting radiopharmaceutical used to treat prostate-cancer-related bone metastasis. The FDA approved Xofigo in May of 2013. The clinical trial that led to the FDA approval was called the ALSYMPCA trial. Eligible patients were randomized in a 2:1 fashion to either receive six monthly intravenous injections of radium-223 or best standard of care, such as antiandrogen hormonal therapy, local external beam radiation, corticosteroids, estramustine, or ketoconazole. The men who received radium-223 had improvement in bone pain and also experienced an increased survival.

Given enzalutamide’s unique and multi-targeted mechanism of action, its once a day oral administration, avoidance of accompanying requirement of a steroid, and its established safety and efficacy data, it appears to be a very promising therapy. Future studies should investigate both combination strategies with other approved prostate cancer drugs, as well as the potential role of enzalutamide in earlier stages of both CRPC and androgen-sensitive prostate cancer.