Background: Proton therapy (PT) has received much public attention due to its higher costs and lack of evidence of clinical benefit compared to intensity modulated radiation therapy (IMRT) for prostate cancer treatment. In this economic study, we performed a threshold analysis to assess the reduction in toxicity that PT would need to achieve compared with IMRT to be considered cost-effective for the treatment of localized prostate cancer.
Methods: SEER-Medicare data was used to identify a cohort, aged 66 years or older, receiving IMRT as definitive radiation therapy (n=4,540). We assumed equal disease control efficacy between IMRT and PT and simulated toxicity outcomes and costs using an incidence-based Markov model. The relative risk of composite toxicity, comparing PT to IMRT, was the efficacy parameter studied. Rates of therapy-induced toxicity associated with IMRT were obtained from SEER-Medicare data. Utility values to calculate quality-adjusted life-years (QALY) and costs (in 2011 US dollars) were obtained from the literature and claims data, respectively. Deterministic threshold analysis using a payer perspective and analytic horizon of 4 years post radiation was performed to determine the relative risk thresholds that would result in incremental cost-effectiveness ratios (ICER) of $50,000 and $100,000/QALY for PT versus IMRT. One-way sensitivity analyses were performed with the lowest and highest treatment costs of PT and IMRT.
Results: Comparing PT against IMRT, the threshold values for the relative risk of composite toxicity were 0.318 and 0.588 at cost-effectiveness levels of $50,000/QALY and $100,000/QALY, respectively. Sensitivity analyses showed that the relative risk needed to achieve an ICER of 100,000/QALY ranged from 0.79 and 0.40 for the low and high cost estimates of PT, and from 0.47 to 0.72, for the low and high cost estimates of IMRT.
Conclusions: Assuming equal disease control, PT would need to result in a 41% reduction in composite toxicity to be considered cost-effective in the treatment of Medicare beneficiaries with localized prostate cancer at a cost-effectiveness threshold of $100,000/QALY.
