Do high glucose levels have differential effect on FDG uptake in inflammatory and malignant disorders?

Background The association of hyperglycaemia with reduced fluorodeoxyglucos e (FDG) uptake by tumour cells is well established. Therefore, it is standa rd practice that all patients must fast for at least several hours prior to FDG positron emission tomography (PET) imaging. However, the effect of hyp erglycaemia on FDG uptake by inflammatory and infectious lesions is unknown . The aim of this study was to investigate this important issue. Methods For in vitro studies human mononuclear cells were isolated from 12 normal volunteers and FDG uptake was determined in medium containing differ ing concentrations of glucose. FDG uptake by human mesothelioma cells was a lso measured for comparison. For studies involving patients, 416 FDG PET sc ans of patients with confirmed malignancy (n = 321) or benign lesions (n = 95) were reviewed retrospectively. The relationship between serum glucose l evel and FDG uptake by the lesions was assessed utilizing the standardized uptake value (SUV) technique. Results In the in vitro studies, while FDG uptake by mesothelioma cells dec reased as glucose concentration increased, there was no differential uptake of FDG uptake by mononuclear cells at glucose concentrations less than 250 mg.dl(-1). In clinical patients, FDG uptake by malignant lesions was sligh tly, but negatively affected by serum glucose level (r = -0.21, P < 0.01) ( glucose range 49-187 mg.dl(-1)). In contrast, FDG uptake by inflammatory le sions was positively associated with serum glucose level (r = 0.43, P < 0.0 1) (glucose range 54-215 mg.dl(-1)). Discussion and conclusion While the degree of FDG uptake is primarily influ enced by the nature of the underlying lesion, serum glucose concentration a ppears to have a small effect on FDG uptake, which differs between malignan t disorders and inflammatory processes. Our data suggest that below a certa in level, elevated glucose concentration might not have a negative effect o n FDG uptake in inflammatory cells, contrary to that observed in malignant disorders. ((C) 2001 Lippincott Williams & Wilkins).