Correlation of tumor-related immunity with 18F-FDG-PET in pulmonary squamous-cell carcinoma

2-Deoxy-2-[fluorine-18] fluoro-d-glucose with positron emission tomography (¹⁸F-FDG-PET) is a clinically useful tool for cancer evaluation. ¹⁸F-FDG accumulation in tumor cells is known to be correlated with the presence of glucose transporter 1 (GLUT1) and hypoxia-inducible factor-1α (HIF-1α). Although anti-programmed death-1 (PD-1) antibody treatments have been approved, no suitable predictor of significant responders has been identified. Based on the existing information, we investigated the relationship between tumor immunity (including PD-L1) and ¹⁸F-FDG uptake in patients with surgically resected pulmonary squamous-cell carcinoma (SQC).

This study included 167 patients (153 men and 14 women) with SQC who underwent ¹⁸F-FDG PET. Tumor sections were stained by immunohistochemistry for GLUT1, HIF-1α, PD-L1, CD4, CD8, and Foxp3. The relationship between clinicopathological features and ¹⁸F-FDG uptake was analyzed. Student's t-test, the χ² test, non-parametric Spearman's rank test and the Kaplan-Meier method were used to show associations between variables.

The rate of positive PD-L1 expression was 79% (132/167), and PD-L1 expression was significantly associated with GLUT1 (P < 0.01), HIF-1α (P < 10^-4), and CD8 (P < 1 × 10^-3) expression. The SUV_max of ¹⁸F-FDG was significantly correlated with PD-L1 (P = 0.02) and GLUT1 (P < 0.01) expression. Multivariate analysis demonstrated that advanced stage, elevated PD-L1 expression, and elevated SUV_max were independent prognostic factors for predicting poor OS. Among patients with a high SUV_max, multivariate analysis confirmed that advanced stage and high PD-L1 expression were independent prognostic factors for poor OS; however, there was no significant difference among patients with a low SUV_max.

High SUV_max on ¹⁸F-FDG-PET is associated with PD-L1 expression but is an independent prognostic factor for OS in our population of surgically resected pulmonary squamous-cell carcinoma.