NIMG-08. 2-HYDROXYGLUTARATE MAGNETIC RESONANCE SPECTROSCOPY IN BRAINSTEM TUMOR PATIENTS IN VIVO

Abstract

Abstract Evaluation of 2-hydroxyglutarate (2HG) by magnetic resonance spectroscopy (MRS) has significant application in assessing the isocitrate dehydrogenase (IDH) mutational status in brain tumor patients noninvasively. This clinical role of 2HG MRS may be demonstrated most clearly in patients with brainstem lesions, where surgical biopsy presents high risk of permanent neurological injury. We conducted 2HG MRS in 20 subjects with a radiographically identified brainstem tumor (13 male and 7 female, age 20 - 73, median age 38). Proton MRS data was acquired from the T2-FLAIR volume using a 2HG-tailored MRS protocol (PRESS TE 97 ms). The millimolar concentration of 2HG was estimated with reference to water. Excluding data with unacceptable quality, data from 16 patients were included in subsequent analysis. The 16 patients were clearly divided into two groups in terms of 2HG level. The tumors in 5 patients showed a clearly discernible 2HG signal (2.25 ppm) while those in 11 patients did not. The 2HG estimation ranged from 2.1 to 6.3 mM in the 5 patients (IDH mutation) and from 0 to 0.7 mM in the 11 patients (most likely IDH wildtype). The mean concentration of 2HG differed significantly between the groups (p=3.3×10−6). One tumor was confirmed to be IDH mutated from autopsy. A representative case for 2HG MRS utility was a patient in whom 2HG was estimated to be 5.3 mM in the first MRS scan and the clinical decision was made to follow with 2HG MRS without surgery and chemoradiation therapy. The patients had 22 follow-up MRS scans for 5.4 years (scan intervals ~3 months), during which the tumor was stable clinically and radiographically. The present study demonstrates the clinical utility of 2HG MRS in brainstem tumors. 2HG MRS provides reliable estimation of 2HG and can be utilized for evaluating the IDH mutation status in brainstem lesion noninvasively.