Baseline disease characteristics were generally similar between treatment arms (Supplementary Table 1), although there were differences in the proportion of patients with an ECOG PS of 0 (pembrolizumab monotherapy vs. EXTREME, 74% vs. 42%; pembrolizumab–chemotherapy vs. EXTREME, 48% vs. 44%), with a PD-L1 tumor proportion score of more than 50% (26% vs. 32% and 8% vs. 38%, respectively), who were current or former smokers (87% vs. 95% and 84% vs. 94%), and who had metastatic disease (87% vs. 89% and 64% vs. 81%). Here, CD274 is linked to metastatic neoplasm.