Predicting programmed death-ligand 1 (PD-L1) expression with fluorine-18 fluorodeoxyglucose ([^18F]FDG) positron emission tomography/computed tomography (PET/CT) metabolic parameters in resectable non-small cell lung cancer

Abstract Background Programmed death-ligand 1 (PD-L1) expression is a predictive biomarker for immunotherapy in non-small cell lung cancer (NSCLC).

PD-L1 and glucose transporter 1 expression are closely associated, and studies demonstrate correlation of PD-L1 with glucose metabolism.

Aim The aim of this study was to investigate the association of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ([^18F]FDG-PET/CT) metabolic parameters with PD-L1 expression in primary lung tumour and lymph node metastases in resected NSCLC.

Methods We conducted a retrospective analysis of 210 patients with node-positive resectable stage IIB–IIIB NSCLC.

PD-L1 tumour proportion score (TPS) was determined using the DAKO 22C3 immunohistochemical assay.

Semi-automated techniques were used to analyse pre-operative [^18F]FDG-PET/CT images to determine primary and nodal metabolic parameter scores (including max, mean, peak and peak adjusted for lean body mass standardised uptake values (SUV), metabolic tumour volume (MTV), total lesional glycolysis (TLG) and SUV heterogeneity index (HISUV)).

Results Patients were predominantly male (57%), median age 70 years with non-squamous NSCLC (68%).

A majority had negative primary tumour PD-L1 (TPS < 1%; 53%).

Mean SUV_max, SUV_mean, SUV_peak and SUL_peak values were significantly higher ( p < 0.05) in those with TPS ≥ 1% in primary tumour ( n = 210) or lymph nodes ( n = 91).

However, ROC analysis demonstrated only moderate separability at the 1% PD-L1 TPS threshold (AUCs 0.58–0.73).

There was no association of MTV, TLG and HISUV with PD-L1 TPS.

Conclusion This study demonstrated the association of SUV-based [^18F]FDG-PET/CT metabolic parameters with PD-L1 expression in primary tumour or lymph node metastasis in resectable NSCLC, but with poor sensitivity and specificity for predicting PD-L1 positivity ≥ 1%.

Clinical relevance statement Whilst SUV-based fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography metabolic parameters may not predict programmed death-ligand 1 positivity ≥ 1% in the primary tumour and lymph nodes of resectable non-small cell lung cancer independently, there is a clear association which warrants further investigation in prospective studies.

Trial registration Non-applicable Key Points • Programmed death-ligand 1 immunohistochemistry has a predictive role in non-small cell lung cancer immunotherapy; however, it is both heterogenous and dynamic.

• SUV-based fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ([ ^ 18 F]FDG-PET/CT) metabolic parameters were significantly higher in primary tumour or lymph node metastases with positive programmed death-ligand 1 expression.

• These SUV-based parameters could potentially play an additive role along with other multi-modal biomarkers in selecting patients within a predictive nomogram.