OBJECTIVES: Radium-223, an intravenously injected radioactive agent, is a new therapeutic option for CRPC patients with symptomatic bone metastases and no known visceral metastatic disease. This budget impact model (BIM) was developed from a United States (US) payer perspective to estimate the economic impact of adding radium-223 to current treatment options in this population. METHODS: An Excel-based BIM evaluated costs of treating CRPC with symptomatic bone metastases and no known visceral metastatic disease with available treatment options (chemotherapies, radionuclides, and oral antiandrogens) in a health plan with and without radium-223. One-year incremental costs were estimated for a hypothetical health plan with 1 million members. The prevalence of metastatic CRPC (mCRPC) patients was obtained from the national registry and published literature. Cost of therapy was obtained from Medicare average sales prices (ASP). Assumptions of outpatient administration and laboratory utilization were derived from product-specific package inserts with costs transformed into costs per 4 weeks based on indicated dosing. Associated costs were derived from the Centers for Medicare & Medicaid Services (CMS) Physician Fee Schedule. RESULTS: An estimated 220 patients were eligible for treatment with radium-223. Radium-223 was assumed to adopt 6.4% of the market in year 1 with equiproportional pull from available treatment options; a cost of $11,500 per 28-day cycle was assumed. In this base-case scenario, costs rose 1.7% ($208,755) or $0.02 per member per month (PMPM) compared to a health plan without radium-223. Sensitivity analyses, varying default inputs ± 10%, showed that results were robust, with greatest sensitivity to the number of radium-223 doses ($0.01–$0.03 PMPM). Other key variables such as cycles of treatment, number of patients treated, and market share resulted in no change to PMPM budget impact. CONCLUSIONS: Economic modeling indicates that adding radium-223 to a health plan’s formulary minimally increases the PMPM cost by $0.02.