Enhanced detectability of recurrent brain tumor using glucose-loading F-18 FDG PET

A 43-year-old man with a history of lung cancer, brain metastasis, and gamma knife radiosurgery underwent FDG PET/CT to differentiate recurrence from radiation necrosis. Basal PET/CT scan showed equivocal uptake in the margin of necrotic tumor. After glucose loading (10% glucose 50 mL for 5 minutes), marginal FDG uptake was more easily depicted. Proton magnetic resonance spectroscopy (1H-MRS) showed increased Cho/Cr ratio (1.7), which was consistent with tumor recurrence. The patient underwent whole brain radiotherapy thereafter. It is implicated that hyperglycemia-induced reduction of glucose uptake in recurrent brain tumors was less than in a normal brain, resulting in higher tumor-to-gray matter ratio.