Cost-Effectiveness of Pembrolizumab Monotherapy for High Programmed Death Ligand 1 Advanced or Metastatic Non-small Cell Lung Cancer Depends on Long-Term Survivors

Background: Pembrolizumab shows effectiveness in treating metastatic non-small cell lung cancer (metNSCLC), with a subgroup of patients experiencing long-term survival (LTS) benefits. The existence of a LTS subgroup may influence the cost-effectiveness of pembrolizumab monotherapy compared with platinum-based chemotherapy. This study aims to assess the potential implications of such a subgroup on the cost-effectiveness for patients with non-squamous metNSCLC and PD-L1 ≥ 50% who are ineligible for targeted therapies. Methods: This study used a decision analytic model based on Dutch real-world data (2008–2014). Two strategies were simulated: (1) a chemotherapy strategy: patients receive chemotherapy in the first-, second-, and third-line; and (2) a pembrolizumab strategy: patients receive first-line pembrolizumab followed by chemotherapy for those progressing to second- and third-lines. The pembrolizumab strategy is evaluated with and without the assumption that there is a LTS subgroup. The LTS subgroup is assumed to be free from metNSCLC-related progression after treatment. Costs (2022 €), including drug costs, other direct medical costs, family costs, and healthcare costs in life years gained, are considered from first-line treatment to death. Effects are measured in quality-adjusted life years (QALYs). The incremental cost-effectiveness ratio (ICER) is assessed using an €80,000/QALY threshold. Threshold analyses are performed on the size and mortality rate of the LTS subgroup and on the price of pembrolizumab. Results: QALYs per patient were 0.65 for chemotherapy, 1.24 for pembrolizumab without LTS, and 3.52 for pembrolizumab with LTS. Average costs per patient were €58,800 for chemotherapy, €154,600 for pembrolizumab without LTS, and €178,600 for pembrolizumab with LTS. Pembrolizumab without LTS was not cost-effective compared with chemotherapy (ICER €167,600/QALY), but pembrolizumab with LTS (30% of simulated population) was cost effective (ICER of €43,100/QALY). Threshold analyses showed that a LTS subgroup size of at least 10% or halving the price of pembrolizumab was needed for pembrolizumab to be cost-effective. Conclusions: Pembrolizumab is a cost-effective first-line treatment for patients with metNSCLC and PD-L1 ≥ 50% in the Netherlands when at least 10% of patients are long-term survivors. Without long-term survivors, this treatment is not cost-effective. Therefore, it is crucial to consider long-term survivors in assessing the cost-effectiveness of immunotherapy in metNSCLC.