Prognostic value of programmed cell death ligand‑1 expression in the tumor‑infiltrating immune cells of patients with lung cancer: A meta‑analysis

Several studies have investigated the prognostic significance of programmed cell death ligand 1 (PD-L1)-positive expression in the tumor cells (TC) of patients with lung cancer. However, tumor-infiltrating immune cell (TIIC)-based PD-L1 expression and its prognostic value remain controversial. The present meta-analysis was performed on 11 studies comprising 2,685 patients, which were identified by a systematic search on the PubMed, PMC, Web of Science and Embase databases. The databases were searched for published articles up to October 30, 2020. The studies that evaluated overall survival (OS) or disease-free survival (DFS) expressed as hazard ratios (HRs) in the PD-L1 TIIC of patients with lung cancer were analyzed. All statistical analyses were conducted using Stata software, version 16.0. The results demonstrated that PD-L1 expression in TIICs was not associated with OS [HR=0.98; confidence interval (CI)=0.73-1.33; P=0.53] and DFS (HR=1.05; CI=0.63-1.77; P=0.42) for all the cohort included in the study. However, subgroup analysis revealed that PD-L1 TIICs were associated with improved OS in lung squamous cell carcinoma (HR=0.76; CI=0.58-0.99; P=0.04), while poorer DFS was observed in lung adenocarcinoma (HR=1.30; CI=1.19-1.43; P=0.008) and at the >1% staining cutoff value (HR=1.56; CI=1.12-2.16; P=0.03). However, poor OS (P=0.21) and DFS (P=0.14) were observed in Asian populations, while DFS (P=0.07) for only-membrane staining was not statistically significant. The results of the present study suggested that adding PD-L1 TIICs to the existing diagnostic algorithm may help to guide patient selection for anti-PD-1/PD-L1 therapy. Future large-scale studies are warranted for confirmation of the present findings.