Hazard ratio of progression-free survival (PFS) (a) and overall survival (OS) (b) using positron emission tomography (PET) parameters. Forest plots describe the hazard ratio regarding the central and peripheral types. PET/CT volumetric parameters such as whole-body metabolic tumour volume and whole-body total lesion glycolysis are independent prognostic factors only in the peripheral type. CI, confidence interval; H-SUVmax, maximum standardized uptake value of the highest lesion of the disease; MTV, metabolic tumour volume; P-SUVmax, maximum standardized uptake value of the primary tumour lesion; TLG, total lesion glycolysis.