Tumor Location Significantly Correlates With PD-L1 Status in Patients With Small Sized Non-small Cell Lung Cancer.

[BACKGROUND/AIM] Predicting programmed death-ligand 1 (PD-L1) expression in resectable lung cancer cases is highly significant for establishing treatment strategies. Although there were differences in tumor characteristics between central and peripheral lesions in non-small cell lung cancer (NSCLC), the relationship between tumor location and PD-L1 expression status has not been examined. We investigated the relationship between clinical background factors, including tumor location, and PD-L1 expression status.

[PATIENTS AND METHODS] A total of 245 NSCLC patients whose tumors were measuring 3 cm or less in diameter and had a consolidation tumor ratio (CTR) <0.5 were included in this study. A tumor was classified as peripheral if its location was in the outer one-third of the computed tomography horizontal section, and as central otherwise. PD-L1 immunohistochemistry was performed using 22C3 antibody. PD-L1 expression status were categorized as negative [PD-L1 tumor proportion score (TPS) <1%] and as positive (PD-L1 TPS ≥1%).

[RESULTS] Statistically significant differences were identified in CTR (=0.006), histology type (<0.001) and tumor location (=0.036) according to the PD-L1 expression status. A greater proportion of patients with a smoking history were observed in the PD-L1 expression positive group (=0.076). Multivariate analysis revealed 0.94< CTR (=0.033), non-adenocarcinoma (=0.018) and central lesion (=0.034) were independent predictive factors for positive PD-L1 expression status. A predictive scoring system incorporating these three factors demonstrated a stepwise increase in PD-L1 positivity with higher scores.

[CONCLUSION] PD-L1 expression status significantly correlated with CTR, histological type and tumor location. This is the first report demonstrating a significant correlation between PD-L1 expression and tumor location in NSCLC. We believe that differences in the cancer microenvironment based on tumor location influence PD-L1 expression status in cancer cells.