Abstract
BACKGROUND: In non-small cell lung cancer (NSCLC), there may be a relationship between programmed death-ligand 1 (PD-L1) expression, driver mutations and cigarette smoking. METHODS: In this single-center retrospective study, the relationship between common driver mutations (EGFR mutation and ALK rearrangement) and PD-L1 expression in advanced NSCLC according to the patients' smoking history was examined. Light, moderate and heavy smokers had smoked < 20, 20-39, and ≥ 40 pack-years, respectively. The level of PD-L1 expression, assessed using Ventana SP263 monoclonal antibody assay, was defined by the tumor proportion score (TPS) as high expression (TPS ≥ 50%), low expression (TPS 1%-49%) and no expression (TPS < 1%). RESULTS: 101 (52.9%) of 191 advanced NSCLC patients were never smokers. EGFR mutations were more common in never smokers (64.4%) than in smokers (17.8%) with advanced NSCLC (P < 0.0001). A higher proportion of smokers (26.7%) had high PD-L1 expression compared to never smokers (13.9%) (P = 0.042). There was a trend for a higher proportion of male NSCLC patients [28 of 115 (24.3%)] than female patients [10 of 76 (13.2%)] to have high PD-L1 expression (P = 0.087]. High PD-L1 expression was seen in 32 of 110 (29.1%) patients with EGFR wild-type NSCLC but only in 6 of 81 (7.4%) patients with EGFR-mutant tumors (P < 0.0001). Among the 90 smokers with NSCLC, a higher proportion of heavy smokers (35.8%) than non-heavy smokers (13.5%) had high PD-L1 expression (P = 0.034). In patients with adenocarcinoma, high PD-L1 expression was seen in 25 of 77 (32.5%) patients with EGFR wild-type tumors but only in 4 of 70 (5.7%) patients with EGFR-mutant tumors (P < 0.0001). Among patients with adenocarcinoma, a significantly higher proportion of ever smokers (29.3%) than never smokers (13.5%) had high PD-L1 expression (P = 0.032). Among smokers with adenocarcinoma, a significantly higher proportion of heavy smokers (44.1%) than non-heavy smokers (8.3%) had high PD-L1 expression (P = 0.004). On multivariate analysis, after adjusting for gender and smoking status, heavy smoking and EGFR wild-type tumors remained significantly associated with high PD-L1 expression in NSCLCs and also in adenocarcinoma. CONCLUSIONS: Heavy smoking and EGFR wild-type tumors were significantly associated with high PD-L1 expression in NSCLCs and also in adenocarcinoma.