BackgroundAtezolizumab has recently been approved for first-line treatment of high PD-L1 expression metastatic Non-Small-Cell Lung Cancer (NSCLC) patients with no EGFR or ALK mutations, on the basis of the IMpower110 trial. This study aims to estimate the cost-effectiveness of atezolizumab compared with pembrolizumab among these patients in Spanish settings, based on the results of the two cut-offs of the IMpower110 study.MethodsA three-state partitioned-survival model was adapted to Spanish settings to calculate health outcomes and costs over a lifetime horizon. Clinical data for atezolizumab were collected from the interim and the exploratory results (data cut-off: Sept'18 and Feb'20, respectively) of the IMpower110 trial while a network meta-analysis was used to model pembrolizumab treatment. Utility data were collected from the trial. Direct medical costs were considered based on resources identified by experts. Costs and outcomes were discounted at 3% per year. Health outcomes were expressed as cost per Life Year (LY) and cost per Quality-Adjusted Life Year (QALY). Both deterministic and probabilistic sensitivity analyses were performed to assess the robustness of results.ResultsOver a lifetime horizon, the incremental results showed that atezolizumab generated similar health outcomes (LYs and QALYs) to pembrolizumab, with minimal differences depending on the cut-off used (+ 0.70 and + 0.42 LYs and QALYs with Sept'18 cut-off and - 0.80 and - 0.72 LYs and QALYs with Feb'20 cut-off). However, for both cut-offs, atezolizumab produced meaningfully less costs than pembrolizumab (euro - 54,261 with Sept'18 cut-off and euro - 81,907 with Feb'20 cut-off). The sensitivity analyses carried out confirmed the robustness of the base-case results.ConclusionsThe cost-effectiveness analysis, comparing the two cut-off of IMpower110, shows that atezolizumab provides similar health gains to pembrolizumab but at a lower cost for the first-line treatment of metastasic NSCLC patients in Spain.