Dissociation between 11C-methionine-PET and Gd-MRI in the longitudinal features of Glioblastoma after postoperative radiotherapy.

Abstract

INTRODUCTION\nThe aims of this study are to compare the longitudinal radiological changes of Glioblastoma multiforme (GBM) after radiotherapy (RT) between 11C-methionine positron emission tomographic (MET-PET) imaging and gadolinium enhanced MRI (Gd-MRI), and to clarify whether these changes predict patient survival.\n\n\nMETHODS\nThis study included 30 patients with newly diagnosed GBM, who received MET-PET and Gd-MRI postoperatively before and every three months after RT (30, 28, and 16 patients were followed for 3, 6, and 9 months after RT, respectively). Regardless of the size after surgery, there remained tumor lesions radiologically in all cases on MET-PET and Gd-MRI. The changes of the lesion/normal brain uptake ratio on MET-PET (L/N ratio) and the contrast enhancing lesion volume on Gd-MRI (Gd-vol) were examined.\n\n\nRESULTS\nThe L/N ratio was decreased until 9 months after RT with significance until 3 months. The Gd-vol was decreased until 3 months and thereafter increased significantly until 9 months. The variation rates (VRs) of the L/N ratio between pre- and 3 months post-RT significantly differentiated patients with survival more than 23 months from those with survival of 23 months or less. The best cut-off value of the VR was -0.366, while providing a specificity of 94.7% and a sensitivity of 60.0%. The median survivals were 39.5 and 17.0 months in patients with a VR of -0.366 or less and those with a VR of more than -0.366.\n\n\nCONCLUSIONS\nThere could be a significant dissociation in the longitudinal changes of GBM after RT between MET-PET and Gd-MRI. The VR of the L/N ratio between pre- and 3 months post-RT, was suggested to be related significantly to patient survival.