Abstract

Objectives

This study aimed to evaluate the cost-effectiveness of pembrolizumab (PEM) for treating patients with advanced colorectal cancer with high microsatellite instability or mismatched repair deficiency in Japan.

Methods

A partitioned survival analysis model was developed to predict costs and quality-adjusted life-years (QALYs) in PEM and standard-of-care (SoC) groups. Survival data for model extrapolation were obtained from the KEYNOTE-177 trial. Drug costs were based on official Japanese pricing, and other medical costs were estimated using a claims database provided by a health insurance association. A 2% discount rate was applied. Utility values were derived from previously published studies. The incremental cost-effectiveness ratio (ICER) of PEM compared with SoC was calculated and evaluated against Japan’s willingness-to-pay threshold. Sensitivity analyses were conducted to assess parameter uncertainty.

Results

The incremental cost of PEM compared with SoC was estimated at JPY15 554 008 with an incremental gain of 2.47 QALYs. Based on these results, the ICER for PEM compared with SoC was JPY6 299 749 per QALY. In a scenario without a restriction on the duration of PEM administration, the ICER was estimated at JPY21 408 155 per QALY.

Conclusions

Although outcomes varied depending on the PEM treatment duration and the medical cost setting after disease progression in the SoC group, PEM was suggested to be more cost-effective than SoC at the reference willingness-to-pay threshold of JPY15 million per QALY in Japan.