Cost-effectiveness of pembrolizumab compared with chemotherapy in the US for women with previously treated deficient mismatch repair or high microsatellite instability unresectable or metastatic endometrial cancer

Aims: There is limited published evidence for the cost-effectiveness of treatments for unresectable or metastatic endometrial cancer (mEC). The objective of this analysis was to assess the cost-effectiveness of pembrolizumab versus chemotherapy for previously treated unresectable or mEC, in women whose tumors have deficient mismatch repair (dMMR) or high microsatellite instability (MSI-H). The analysis was carried out from a US healthcare payer perspective.

Materials and methods: A lifetime partitioned survival model comprising three health states (progression-free, progressed disease and death) was constructed. Chemotherapy was represented by single-agent paclitaxel or doxorubicin. Overall survival, progression-free survival and time on treatment data for pembrolizumab were obtained from a Phase II clinical study that included women with previously treated dMMR/MSI-H unresectable or mEC (KEYNOTE-158, NCT02628067). Survival data for chemotherapy were obtained from a published Phase III study for previously treated advanced endometrial cancer. Costs included were drug acquisition and administration, health-state, end-of-life, and adverse event management. Costs were presented in 2019 US$. Outcomes were calculated as quality-adjusted life-years (QALYs), using EQ-5D data from KEYNOTE-158. Model results were tested extensively in deterministic and probabilistic sensitivity analyses.

Results: Results demonstrated that pembrolizumab is a highly cost-effective treatment option when compared with chemotherapy, with estimated deterministic and probabilistic incremental cost-effectiveness ratios (ICERs) of $58,165 and $57,668 per QALY gained, respectively. Pembrolizumab was associated with a large QALY and life-year gain per person versus chemotherapy over the model time horizon (deterministic 4.68 life year gain, 3.80 QALYs), with the majority of QALYs accrued in the progression-free health state.

Limitations: The key limitation of the analysis was the lack of comparative effectiveness data for pembrolizumab versus chemotherapy.

Conclusions: Pembrolizumab is a highly cost-effective treatment option when compared with chemotherapy for women with previously treated dMMR/MSI-H unresectable or mEC. Results were robust to the changes in parameters and assumptions explored.