Cancer immunotherapy targeting programmed cell death-1/programmed cell death ligand-1 (PD-1/PD-L1) pathway has shown promising results in treatment of non-small cell lung cancer (NSCLC) patients. T cells play a major role in tumor-associated immune response. This study aimed to investigate PD-L1 expression alone and combined with CD8 tumor infiltrating lymphocytes (TILs) density in relation to clinicopathologic parameters and survival in NSCLC patients. Immunohistochemical analysis was used to evaluate PD-L1 expression and CD8 TILs density in 55 NSCLC patients. PD-L1 immunopositivity was detected in 36 (65.5%) of NSCLC cases. PD-L1 expression was significantly related to high tumor grade (p value = 0.038) and low CD8 TILs density (p value = 0.004), whereas no significant relations were detected between PD-L1 expression and tumor stage (p value = 0.121), overall survival (OS) (p value = 0.428) and progression-free survival (PFS) (p value = 0.439). Among PD-L1/CD8 TILs density groups, PD-L1⁺/CD8^Low group was significantly associated with high tumor grade compared to PD-L1^-/CD8^high group (pairwise p = 0.016). PD-L1⁺/CD8^Low group was significantly related to advanced tumor stage compared to PD-L1⁺/CD8^high and PD-L1^-/CD8^Low groups (pairwise p = 0.001 and 0.013 respectively). PD-L1^-/CD8^high group exhibited the best OS and PFS whereas PD-L1⁺/CD8^low group had the poorest OS and PFS (p value = 0.032 and 0.001 respectively). Assessment of PD-L1 combined with CD8 TILs density, instead of PD-L1 alone, suggested important prognostic relevance in NSCLC patients.

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