Comprehensive analysis of PD-L1 in non-small cell lung cancer with emphasis on survival benefit, impact of driver mutation and histological types, and archival tissue

Background The aim of the study was to assess programmed death-ligand-1 (PD-L1) expression in different histological types and gene mutation status of patients with non-small cell lung cancer (NSCLC). Methods A total of 4062 pathology-confirmed lung cancer patients were retrospectively screened at Kaohsiung Chang Gung Memorial Hospital from November 2010 to June 2017. There were 699 NSCLC patients with confirmed PD-L1 expression level retrospectively enrolled for analysis. Results There was a trend of higher PD-L1 expression in squamous cell carcinoma and adenosquamous cell carcinoma than in adenocarcinoma (p = 063). Significant higher PD-L1 expression in EGFR wild-type was noted (p < 0.001). No significant differences in PD-L1 expression were found between ALK wild- and mutant types, but there seem was a trend of high PD-L1 level noted in ALK mutation patients (p = 0.069). In EGFR mutation patients, a higher time to treatment failure (TTF) duration was observed in no PD-L1 expression (p = 0.011). Longer tumor tissue storage time correlated with lower PD-L1 expression in lung cancer (p < 0.001 for linear trend). Conclusions There were a trend or significant differences in PD-L1 expression between different histological types in NSCLC, different EGFR and ALK status, and different tumor tissue storage time. A higher survival benefit was observed in no PD-L1 expression than with PD-L1 expression in adenocarcinoma, EGFR and ALK mutation patients. We recommend that PD-L1 assay should be performed as early as possible if tissue is available.