OBJECTIVES: Pembrolizumab was shown to significantly prolonged progression-free survival compared to chemotherapy in patients with advanced colorectal cancer with MSI-High or dMMR. This study aimed to evaluate the cost-effectiveness of pembrolizumab from the perspective of Japanese payers.

METHODS: A partitioned survival analysis model was developed to predict costs and quality-adjusted life years (QALYs) in pembrolizumab and chemotherapy group. Survival data were derived from the PhaseⅢ KEYNOTE-177 study. Drug prices were estimated based on the Japan’s NHI drug price. Other cost parameters were estimated by using the JMDC claims database. Utility weights were derived from previous studies. Lifetime horizon and discount rate of 2% was applied. The incremental cost-effectiveness ratio (ICER) of pembrolizumab compared with chemotherapy was estimated. Sensitivity analyses were performed to assess parameter uncertainty.

RESULTS: The incremental cost of pembrolizumab compared to chemotherapy was estimated to be -JPY 15,409,646 and the incremental QALY was 2.51, resulting in pembrolizumab being dominant. If the 2-year discontinuation rule for pembrolizumab was eliminated, the ICER was estimated to be JPY14,891,339/QALY. If the cost of subsequent treatment in the chemotherapy arm did not include pembrolizumab cost, the ICER was estimated to be JPY1,157,159/QALY. After adjusting for the effect of crossover with pembrolizumab on OS in the chemotherapy arm, the ICER was estimated to be JPY4,276,547/QALY.

CONCLUSIONS: Although results varied depending on the treatment duration with pembrolizumab and the subsequent treatment setting in chemotherapy arm, pembrolizumab was cost-effective compared to chemotherapy when the willingness-to-pay threshold of 15 million/QALY was applied.