Aim: The study aim was to evaluate the cost effectiveness of pembrolizumab monotherapy compared with chemotherapy as a first-line treatment for previously untreated metastatic non-small cell lung cancer (NSCLC) with programmed death ligand-1 (PD-L1) tumour proportion score (TPS) ≥50%, from a Swiss payer perspective. Cost effectiveness of pembrolizumab for this indication has not previously been evaluated in Switzerland.
Methods: We conducted an analysis using a partitioned survival model with a cycle length of one week, base-case time horizon of 20 years and discount rate of 3% for cost and health outcomes. KEYNOTE-024 randomised controlled trial data for pembrolizumab monotherapy compared with chemotherapy was used as a basis for projecting time-on-treatment, progression-free survival and overall survival, over a 20-year period. For overall survival and progression-free survival, we used Kaplan-Meier probabilities for a brief initial period of the model, followed by parametric curves that had the best fit with subsequent trial data. Quality-adjusted life years (QALYs) were calculated based on the EuroQol 5-dimensional 3-level (EQ-5D-3L) questionnaire administered to trial patients. Costs (in CHF, year 2018) of drug acquisition/administration, adverse events and disease management were included.
Results: For the base-case, pembrolizumab monotherapy resulted in mean incremental costs of CHF 77,060 (pembrolizumab CHF 223,324, chemotherapy CHF 146,264) and mean incremental QALYs of 1.34 (pembrolizumab 3.05, chemotherapy 1.71), leading to an incremental cost-effectiveness ratio of CHF 57,402 per QALY gained. Cost-effectiveness results were most sensitive to overall survival and relatively insensitive to other parameters varied. In probabilistic sensitivity analysis, the probability of cost effectiveness of pembrolizumab, with an assumption of a willingness-to-pay threshold of CHF 100,000 per QALY gained, was 88%.
Conclusion: Pembrolizumab is likely to be cost effective for treating Swiss patients with previously untreated metastatic NSCLC expressing PD-L1 TPS ≥50%. (This economic evaluation was based on the KEYNOTE-024 trial. The trial identifier is NCT02142738.).