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Usefulness of Semiquantitative FDG-PET in the Prediction of Brain Tumor Treatment Response to Gamma Knife Radiosurgery

Purpose The aim of this study is to evaluate whether posttreatment FDG-PET can predict the treatment response to gamma knife radiosurgery (GKRS) for patients with gliomas. Method Eighteen patients with histologically confirmed gliomas treated by GKRS and followed for more than 24 months were enrolled in this study. All patients underwent FDG-PET 6–8 months after GKRS. PET images and MR images were integrated and tumor-to-cortex (T/C) and tumor-to-white matter (T/WM) FDG uptake ratios were measured. By estimating the change of the maximum tumor diameter measured on the contrast-enhanced MRI (the last follow-up MRI vs. the pre-GKRS MRI), the tumor response was classified as complete remission, partial remission (PR), stable disease (SD), and progression of disease (PD). Group 1 includes four tumors with PR and 6 tumors with SD; group 2 includes 8 tumors with PD after GKRS. Results Both mean T/C ratio and mean T/WM ratio of group 1 patients are statistically less than those of group 2 patients. Conclusion Our study suggests that, for patients with gliomas treated by GKRS, the posttreatment FDG-PET may be useful to predict the treatment response.