Correlation of 18F-FDG-PET/CT metabolic parameters with PD-L1 tumour proportion score (TPS) in resected non-small cell lung cancer (NSCLC)

Introduction: Immune checkpoint inhibitors targeting the PD-1/PD-L1 axis play a significant role in the adjuvant and metastatic treatment of non-small cell lung cancer (NSCLC). PD-L1 is an important biomarker but is dynamic and heterogeneously expressed. Metabolic parameters of 18F-FDG-PET/CT, including SUVmax and total lesion glycolysis (TLG), have been shown to correlate with PD-L1 expression in advanced NSCLC. However, the relationship in early stage NSCLC remains unclear. Methods: This retrospective study evaluated pre-surgery 18F-FDG-PET/CT scans in a cohort of NSCLC patients who underwent primary tumour and hilar/mediastinal nodal resection at a London cancer centre. Pre-surgery scans were assessed for tumoural maximum standardised uptake value (SUVmax), SUVmean, SUVpeak, SULpeak, metabolic tumour volume (MTV), TLG and SUV-based heterogeneity index (HISUV=x/y). PD-L1 TPS was assessed in resected primary tumour samples using 22C3 pharmDx DAKO assay. Unpaired t-test, one-way ANOVA or Kruskall-Wallis tests were applied to determine the relationship between 18F-FDG-PET/CT metabolic parameters and primary PD-L1 TPS score. Results: 100 consecutive NSCLC patients with pre-surgical 18F-FDG-PET/CT and primary NSCLC resection specimens were included. Patients were grouped by primary tumour PD-L1 TPS of <1% (n=45),1-49% (n=37) and ≥50% (n=18). There was no statistical difference between PD-L1 TPS groups for primary tumour SUVmax (p=0.38), SUVmean (p=0.48), SUVpeak (p=0.91), SULpeak (p=0.88), MTV (p=0.06), TLG (p=0.21) and HISUV (p=0.07). Non-significance also held using PD-L1 TPS cut offs of < or ≥1% and < or ≥50%.Conclusions: In this preliminary study, there was no correlation between 18F-F DG-PET/CT metabolic parameters and PD-L1 TPS score of primary tumour in resected NSCLC. Further work will investigate the use of 18F-FDG-PET/CT in determining PD-L1 expression of nodal metastases in early resected NSCLC.