Patterns of PD-L1 expression and tumor infiltrating immune cells in resected NSCLC

<bold>Background:</bold> Recent studies have confirmed, that immunotherapy was effective in early-stage NSCLC, but the selection of patients remains challenging. Further research of programmed death–ligand 1 (PD-L1) expression in the context of tumor microenvironment (TME) is needed. <bold>Methods:</bold> 72 archival tissue specimens of surgically resected I-III stage NSCLC, that were already evaluated for tumor infiltrating lymphocytes and macrophages, were assessed for PD-L1 expression by three scoring methods: tumor proportion score (TPS), immune cell score (IC) and combined proportion score (CPS). <bold>Results:</bold> PD-L1 expression >1% evaluated by TPS, IC and CPS was detected in 28%, 36% and 39% cases. Moderate, substantial and strong agreement between TPS and IC, TPS and CPS, CPS and IC was detected (Cohen’s κ coefficient 0.556, 0.63 and 0.941). PD-L1 TPS, IC and CPS correlated with smoking intensity (<italic>p</italic>=0.012; <italic>p</italic>=0.013 and <italic>p</italic>=0.002), whereas only PD-L1 TPS was associated with squamous histology (<italic>p</italic>=0.028). PD-L1 IC >1 % was more often seen in tumors with high CD4⁺ T cells infiltration (<italic>p</italic>=0.02), while PD-L1 CPS >1% - in tumors with high CD4⁺ and CD8⁺ T cells infiltration (<italic>p</italic>=0.021 and <italic>p</italic>=0.048). PD-L1 IC and CPS ≥10 % was more often detected in tumors with higher CD4+Foxp3+ T cells infiltration (<italic>p</italic>=0.01 and <italic>p</italic>=0.025). PD-L1 TPS ≥50 % was associated with higher tumor infiltrating M2 macrophages count (<italic>p</italic>=0.021). However, we found no association between PD-L1 in the context of TME and survival. <bold>Conclusions:</bold> Significant correlations among TPS, IC and CPS were detected. PD-L1 expression was associated with smoking intensity, squamous histology and tumor infiltrating CD4⁺ T cells, CD4⁺Foxp3⁺ T cells, CD8⁺ T cells and M2 macrophages.