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.