1H-MRS in vivo predicts the early treatment outcome of postoperative radiotherapy for malignant gliomas

Purpose: To analyze prospectively the prognostic significance of 1H magnetic resonance spectroscopy (MRS) in vivo recorded from the tumor bed of patients after surgery for malignant glioma. Methods and Materials: Fifty-one patients aged 20-68 years were examined using a MRI/MRS system (Elscint 2T Prestige). Of the 51 patients, 33 had Grade 3 gliomas and 18 had glioblastomas. MRI-localized 1HMR spectra were acquired using a single-voxel, double-spin-echo sequence. Relative intensities of the signals (choline, creatine [Cr] N-acetyl aspartate [NAA], myo-inositol, lactate, and lipids) were obtained by numeric integration of fitted signals. Two voxels were examined, one located at the tumor bed and the second distant to the tumor bed. All patients were irradiated to 60 Gy using three-dimensional conformal noncoplanar techniques to 60 Gy. Results: MRS in vivo in patients after brain tumor surgery revealed a statistically significant decrease in the NAA/Cr ratio and increases in the choline/creatine (Cr), choline/NAA, and myo-inosytol/Cr ratios. The intensive signals of lactate and lipids appeared in spectrum. Survival correlated strongly with tumor grade and patient age but the strongest prognostic factor was the lactate/NAA ratio. For lactate/NAA values >2.0 (intensive lactate signal) the 1-year survival rate was 20%, and for lactate/NAA values <2.0, the 1-year survival rate was 85%. Conclusion: A new diagnostic tool demonstrated ability to distinguish between patients with a favorable prognosis and those who will die within 1 year