Yoon BW, Chang B, Lee SH., et al. - In patients with epidermal growth factor receptor-mutated lung cancer, researchers investigated if there was any relationship between programmed death-ligand 1 (PD-L1) expression and treatment results when managed with tyrosine kinase inhibitors. Overall 131 patients with EGFR-mutant, advanced lung adenocarcinoma were examined; of those, the proportion having PD-L1 tumor proportion score (TPS) ≥ 50%, was 17.6%, while 32.8% had a 1– 49% TPS, and 49.6% had a < 1% TPS. The group with PD-L1 TPS ≥ 50% had a significantly lower response rate vs the other groups. PD-L1 TPS ≥ 50% vs PD-L1 TPS < 50% independently correlated with a significantly shorter PFS in the overall population and with shorter OS in patients with exon 19 deletion, as seen in multivariate analysis. The group with PD-L1 TPS ≥ 50% had a significantly reduced frequency of secondary T790M mutation following TKI failure vs other groups. Study results indicate that patients high PD-L1 expression are a distinct subgroup that deserve active surveillance and a customized treatment approach.