Cost-Utility Analysis of Durvalumab and Tremelimumab Versus Best Supportive Care in Refractory Metastatic Colorectal Cancer

Objectives To determine the cost-effectiveness of combined durvalumab and tremelimumab in patients with metastatic colorectal cancer in the intention-to-treat (ITT) and biomarker-enriched populations using direct CCTG CO.26 phase-2 trial data. Methods A 4-state microsimulation model was used to evaluate the expected health outcomes in quality-adjusted life years (QALYs) and costs (2023 Canadian Dollars) over a lifetime horizon (5 years) from the Canadian public-payer perspective. Direct phase 2 CCTG CO.26 trial data informed model inputs, including overall survival Kaplan-Meier curves, progression-free survival Kaplan-Meier curves, and adverse event rates. Health-state utilities and costs of therapy, hospitalization, end-of-life care, sequencing panels, and physician care were obtained from published literature and Canadian costing databases. The incremental cost-utility ratios (ICURs) for the ITT and biomarker-enriched populations were determined. Results In the ITT population, expected QALYs for the treatment and best supportive care arms were 0.47 and 0.33 (incremental (Δ)0.14), respectively, and expected costs were $56 743 and $17 177 (Δ$39 566) for an ICUR of $277 661/QALY. In the plasma tumor mutation burden > 28 subgroup, expected QALYs were 0.43 and 0.21 (Δ0.21) and expected costs were $58 498 and $16 941 (Δ$41 557) for an ICUR of $193 945/QALY. Conclusions Combined durvalumab and tremelimumab is not cost-effective in refractory metastatic colorectal cancer per conventional cost-effectiveness thresholds. Cost-effectiveness is more favorable in the high-plasma tumor mutation burden subgroup, but costs of screening and cutoffs used must be considered.