Programmed death-ligand 1 (PD-L1) expression is not a completely reliable predictive marker of the efficacy of anti–programmed cell death protein-1 (PD-1)/PD-L1 therapy in patients with advanced NSCLC. Immune-related tumor microenvironment (TME) is classified into four different types based on the tumor-infiltrating lymphocyte (TIL) status and PD-L1 expression.

We retrospectively reviewed patients with advanced NSCLC treated with anti–PD-1/PD-L1 therapy between 2015 and 2019. We investigated the association between the efficacy of anti–PD-1/PD-L1 therapy, the types of TME based on PD-L1 (clone: 22C3) expression, the density of CD8-positive TILs assessed by immunohistochemistry, and mutational profiles by next-generation sequencing.

Overall, 228 patients were included in the analysis. The patients were classified into the following four groups: type I: PD-L1_High (tumor proportion score ≥ 50%)/TIL_High (≥85/mm²; n = 73); type II: PD-L1_Low (tumor proportion score < 50%)/TIL_Low (<85/mm²; n = 70); type III: PD-L1_High/TIL_Low (n = 37); and type IV: PD-L1_Low/TIL_High (n = 48). The objective response rate (ORR) and progression-free survival (PFS) of anti–PD-1/PD-L1 therapy clearly differed according to the different TME types (ORR and PFS; type I: 64%, 14.5 mo; type II: 12%, 2.1 mo; type III: 24%, 3.6 mo; type IV; 41%, 10.8 mo). In patients with PD-L1_High tumors, type I tumors had significantly better ORR and PFS than type III tumors (ORR: p < 0.001 and PFS: p < 0.001). The presence of TP53 and KRAS mutation was related to the density of CD8-positive TILs and PD-L1 expression, respectively.

Differential types of TME, including PD-L1 expression and TIL status, could accurately predict the efficacy of anti–PD-1/PD-L1 therapy.