Cost-Effectiveness Threshold of Magnetic Resonance Image-Guided Radiotherapy for Localized Prostate Cancer

Abstract

Magnetic resonance image guided radiotherapy (MR-IGRT) is anticipated to reduce toxicity through intrafraction motion detection and smaller treatment margins, but no studies have assessed if the technology can be cost-effective. Our purpose is to determine if MR-IGRT for treatment of localized prostate cancer can achieve cost-effectiveness through toxicity reduction alone compared to CT-based image guided radiotherapy (CT-IGRT). The comparison groups were MR-IGRT and CT-IGRT delivered in conventional 39 fraction and stereotactic body radiotherapy (SBRT) 5 fraction schedules. To determine the cost of delivering radiotherapy to each group, time driven activity-based costing was used with a healthcare cost perspective. Equipment and therapy-related costs for each group were calculated with data from two institutions and literature values assuming a 15-year lifespan per machine and utilization of treatment machines 8 hours/day, 5 days/week, 50 weeks/year. The gastrointestinal and genitourinary toxicity rates associated with CT-IGRT in this model were averaged from 20 prior studies. The costs and utilities associated with various health states were obtained from literature values and cost databases. Markov modeling was used to determine the costs and quality adjusted life years (QALYs) saved with each 1% relative reduction in acute and chronic toxicities by MR-IGRT over 15 years with a discount rate of 3%. Toxicity reduction thresholds for cost-effectiveness were then calculated based on the added cost of MR-IGRT juxtaposed with the cost reduction and QALYs saved for each 1% relative toxicity reduction from Markov modeling. One-way sensitivity analyses were performed. Standard $50,000 and $100,000 per QALY ratios were used. The added cost of MR-IGRT over CT-IGRT was $1,459 per course of SBRT and $10,129 per course of conventionally fractionated radiotherapy. Relative toxicity reductions of 7% and 14% were required for MRI-guided SBRT to be cost-effective compared to CT-guided SBRT using $100,000 and $50,000 per QALY, respectively. MR-IGRT in conventional fractionation required relative toxicity reductions of 50% and 94% to be cost-effective at $100,000 and $50,000 per QALY. In the sensitivity analyses, the cost-effectiveness of MR-IGRT was most dependent on the number of patients treated on the MR-IGRT and CT-IGRT systems as well as the initial and maintenance costs of the MR-IGRT system. From a healthcare perspective, MR-IGRT can be cost-effective through toxicity reduction alone. Hypofractionated schedules, such a five fraction SBRT, are most likely to achieve cost-effectiveness as they require only slight reductions in toxicity (7-14%).