Dr. Sartor on the Mechanism of Action of Radium-223

A. Oliver Sartor, MD, the medical director of the Tulane Cancer Center, describes the mechanism of action of radium-223, which was recently approved to treat patients with bone metastatic castration-resistant prostate cancer.

Radium-223 is unlike any other drug, Sartor believes. It is an alpha-emitter, which is a unique form of radiation that is highly energetic with a short range. As such, radium-223 is capable of delivering a high dose of radiation therapy in a very focused way.

Additionally, Sartor adds, as a calcium mimetic, radium-223 binds to osteoblastic metastases. When these occur, an organic followed by an inorganic matrix is laid down. The inorganic matrix is then filled with hydroxyapatite, to which radium-223 binds. The agent does not actually bind to the tumor, Sartor notes, it does, however, bind to and irradiate the regions around the tumor, initiating an antitumor effect.