Radium-223 chloride: a potential new treatment for castration-resistant prostate cancer patients with metastatic bone disease

Michael R Harrison, Terence Z Wong, Andrew J Armstrong, Daniel J GeorgeDuke Cancer Institute, Durham, NC, USABackground: Radium-223 chloride (223Ra; Alpharadin) is an alpha-emitting radioisotope that targets areas of osteoblastic metastasis and is excreted by the small intestine. When compared with beta-emitters (eg, strontium-89, samarium-153), 223Ra delivers a high quantity of energy per track length with short tissue penetration.Objective: This review describes the mechanism, radiobiology, and preclinical development of 223Ra and discusses the clinical data currently available regarding its safety and efficacy profile.Methods: Data from clinical trials including abstracts were collected and reviewed using the PubMed Database, as well as the American Society of Clinical Oncology abstract database.Conclusion: Current bone-targeted therapies fall into two main categories: antiresorptive agents (eg, zoledronic acid, denosumab), which have been shown to delay skeletal-related events, and radiopharmaceuticals (eg, samarium-153), which may have a role in pain palliation. Historically, neither antiresorptive agents nor radiopharmaceuticals have shown definitive evidence of improved overall survival or other antitumor effects in metastatic castrate-resistant prostate cancer (mCRPC). Radiopharmaceuticals are limited by myelosuppresion, thrombocytopenia, and renal excretion. In a recently reported randomized Phase III trial in men with symptomatic bone-metastatic CRPC who had received or were ineligible for docetaxel chemotherapy, 223Ra treatment resulted in improved overall survival and delayed skeletal-related events. Toxicity consisted of minor gastrointestinal side effects and mild neutropenia and thrombocytopenia that were rarely severe. Pending regulatory approval, 223Ra may represent a unique and distinct option for an important subgroup of patients with mCRPC; future trials should address its use in combination or in sequence with existing and novel agents.Keywords: Alpharadin, 223Ra, radium-223, radionuclide therapy, metastatic castrate-resistant prostate cancer, bone metastase