The addition of immune checkpoint inhibitors (ICIs), pembrolizumab or dostarlimab, to paclitaxel and carboplatin (TC) has shown better response rates and survival outcomes for patients with primary advanced mismatch repair-deficient (MMRd) endometrial cancer (EC) in NRG-GY018 and RUBY, respectively. Nonetheless, the high cost of ICIs remains a major concern when implementing this strategy in the real world. This study aimed to determine the cost-effectiveness of pembrolizumab and dostarlimab with chemotherapy compared to TC for primary advanced MMRd EC.

We developed a Markov model including 6600 patients with primary advanced MMRd EC to simulate treatment outcomes. The initial decision points in the model were treatment with pembrolizumab with TC (PEM-TC), dostarlimab with TC (DOS-TC), and TC. Model probabilities, costs, and health utility values were derived with assumptions from published literature. Effectiveness was determined as average quality-adjusted life years (QALYs) gained. The primary outcome was the incremental cost-effectiveness ratio (ICER).

TC was the least costly strategy, whereas PEM-TC was the most effective strategy for primary advanced MMRd EC. TC was cost-effective based on a willingness-to-pay (WTP) threshold of $100,000/QALY compared with PEM-TC (ICER, $377,718/QALY), and DOS-TC exhibited absolute dominance (ICER, $401,859/QALY). PEM-TC was cost-effective when the cost of pembrolizumab 200 mg was reduced to $4361 (61% reduction). PEM-TC was selected in 16.5% with a WTP threshold of $300,000/QALY, but in <1% with a WTP threshold range of $100,000-200,000/QALY.

PEM-TC can become cost-effective for primary advanced MMRd EC when the cost of pembrolizumab substantially decreases.