Oliver Sartor, MD, medical director, Tulane Cancer Center, discusses the novel molecule radium-223 (Alpharadin) that emits alpha particles, a type of ionizing radiation that contains 2 protons and 2 neutrons. The molecule commonly binds to calcium receptors and appears prominently in osteoblastic bone lesions.

Radium-223 is currently being investigated for prostate cancer with bone metastases. Preliminary phase I/II data showed that radium-223 was safe with relatively high efficacy and decreased the median time to prostate-specific antigen (PSA) progression, reduced bone alkaline phosphatase levels, and decreased the pain associated with bone metastases.

These results prompted a large phase III trial named ALpharadin in SYMptomatic Prostate CAncer (ALSYMPCA). It contained 922 patients with hormone refractory prostate cancer and bone metastases. At an interim analysis the data monitoring committee determined that overall survival was prolonged.

The trial was terminated early because of the positive results and patients on the placebo arm were allowed to cross over to receive radium-233. Based on the positive ALSYMPCA trial radium-223 is being prepared for regulatory approval.