CD8A and neoplasm: Furthermore, this is possibly linked to other tumour suppression pathways as expression of programmed death ligand-1 (PD-L1) has been shown to promote cellular pathways that drive tumour glycolysis.107 Positive correlations between 18F-FDG and PD-1/L1 expression in lung cancer and CD8 T cell infiltration have also been demonstrated.108,109 However, 18F-FDG cannot be considered as a clinically reliable surrogate for either as correlations were too weak for statistical significance.