P2.02-026 Impact of PD-L1 Expression on 18F-FDG-PET in Pulmonary Squamous Cell Carcinoma

2-deoxy-2-[fluorine-18] fluoro-D-glucose integrated with positron emission tomography (18F-FDG-PET) is clinically useful for the evaluation of cancer. The accumulation of 18F-FDG within tumor cells is implicated in the expression of glucose transporter 1 (GLUT1) and hypoxic inducible factor-1α (HIF-1α). Although anti-programmed death-1 (PD-1) antibody therapy is approved for non-small cell lung cancer (NSCLC), the predictive biomarkers remain unknown. It was recently reported that the expression of programmed death ligand 1 (PD-L1) was positively correlated with the expression of GLUT1 and HIF-1α. Based on these backgrounds, we investigated the relationship between the tumor immunity including PD-L1 expression and the degree of 18F-FDG uptake in surgically resected pulmonary squamous cell carcinoma (SQC). One hundred and sixty-seven patients (153 men, 14 women) with SQC who underwent 18F-FDG PET were included in this study. Tumor sections were stained by immunohistochemistry for GLUT1, HIF-1α, PD-L1, CD4, CD8, and Foxp3. Relationships of clinicopathological and molecular biological features to the degree of FDG uptake and survival were analyzed. The SUVmax of 18F-FDG was significantly correlated with the expression of PD-L1 (p=0.0224) and GLUT1 (p=0.0075). The PD-L1 expression was significantly correlated either with GLUT1 (p=0.0059), HIF-1α (p<0.0001) or CD8 (p=0.0006). Other pairs exhibiting significant correlation are as follows: GLUT1 and HIF-1α (p=0.0072), HIF1α and CD8 (p=0.0072), CD8 and Foxp3 (p<0.0001). Univariate analysis demonstrated that advanced stage (p=0.0027), elevated SUVmax (p=0.0233), and elevated PD-L1 expression (p=0.0157) were associated with unfavorable overall survival (OS). Multivariate analysis also revealed that advanced stage (p=0.0445), elevated SUVmax (p=0.0382), and elevated PD-L1 expression (p=0.0173) were independent prognostic factors predicting unfavorable OS. 18F-FDG uptake was significantly correlated with the expression of PD-L1 and GLUT1 in SQC. 18F-FDG PET may reflect the immune response in the tumor microenvironment involved in the regulation of PD-L1 expression.