Dissociation Between 11C-Methionine-Positron Emission Tomography and Gadolinium-Enhanced Magnetic Resonance Imaging in Longitudinal Features of Glioblastoma After Postoperative Radiotherapy

The aims of the present study were to compare the longitudinal changes of glioblastoma multiforme after radiotherapy (RT) between 11C-methionine positron emission tomography (MET-PET) and gadolinium (Gd)-enhanced magnetic resonance imaging (MRI) and to clarify whether these changes were predictive of survival. We included 30 patients, who had undergone MET-PET and Gd-MRI before and every 3 months after RT. The lesion/normal brain uptake (L/N) ratio and contrast-enhancing lesion volume were examined. The L/N ratio was decreased until 9 months after RT with significance until 3 months. The contrast-enhancing lesion volume was decreased until 3 months and thereafter increased until 9 months with significance. The variation rates of the L/N ratio between pre-RT and 3 months differentiated survival of >23 months from ≤23 months. A dissociation could exist in the longitudinal changes of GBM after RT between MET-PET and Gd-MRI. The variation rate of the L/N ratio could be related to survival.