Abstract
2-Deoxy-2-[fluorine-18] fluoro-d-glucose (18F-FDG) positron emission tomography (PET) is a useful modality for the assessment of tumour glucose metabolism by upregulation by hypoxia. Little is known whether the uptake of 18F-FDG within cancer cells is linked to the expression of programmed death ligand-1 (PD-L1), a predictor of anti-PD-1 antibody. We conducted a clinicopathological study to assess the expression of PD-L1 and tumour-infiltrating lymphocytes (TILs) in patients with surgically resected pulmonary adenocarcinoma (AC) who received preoperative 18F-FDG PET. A total of 315 patients with lung AC who received 18F-FDG PET were enrolled in the study. Tumour specimens were stained by immunohistochemistry for glucose transporter 1 (Glut1), hypoxia-inducible factor-1α (HIF-1α), PD-L1, CD4 and CD8. We assessed whether the uptake of 18F-FDG was correlated with clinicopathological variables. PD-L1 was highly expressed in 60% of all patients with AC, and the expression level was significantly correlated with 18F-FDG uptake, glucose metabolism and hypoxia. PD-L1 and the maximum standardised uptake value (SUVmax) were identified as independent prognostic predictors by multivariate analysis. In particular, PD-L1 could be a significant marker for predicting worse outcomes in AC patients with high 18F-FDG uptake but not in those with low 18F-FDG uptake. According to the epidermal growth factor receptor (EGFR) mutation status, the expression of PD-L1 was significantly correlated with SUVmax in patients with EGFR mutation, whereas, PD-L1 was a significant predictive negative factor in those with wild-type EGFR. 18F-FDG uptake was significantly correlated with PD-L1 expression, and the latter was closely linked to the presence of glucose metabolism and hypoxia in patients with pulmonary AC.