High level of programmed death ligand 1 (PD-L1) predicts longer survival in patients with resectable small cell lung cancer.

: The purpose of this study was to investigate the association between the expression of programmed cell death ligand 1 (PD-L1) and the survival of patients with small cell lung cancer (SCLC) who had undergone complete resection. Formalin-fixed, paraffin-embedded tumor tissue samples from 61 patients with resected SCLC were stained with an anti-PD-L1 antibody (SP142) by immunohistochemistry (IHC) and scored according to staining intensity and the percentage of tumor cells staining positive for PD-L1. The PD-L1 positive threshold in tumor cells was defined as ≥ 5%. The percentage of positive PD-L1 staining in all SCLC specimens was 44.3% (27/61). The median survival time of patients with PD-L1-positive tumors was significantly longer than those with PD-L1-negative tumors (not reached vs. 34 months, P = 0.032). Multivariate analysis indicated that postoperative chemotherapy (HR = 0.322, P = 0.023) and PD-L1 expression ≥ 5% (HR = 0.253, P = 0.008) were independent prognostic factors for overall survival. The results suggest that PD-L1 expression is readily detectable in the tumor tissues of SCLC, and that PD-L1 expression can predict the survival of these patients.