University of Toronto
Glioblastoma is the most common primary malignant
neoplasm in adults, with a median survival of 15-18 months after diagnosis. Our group has previously demonstrated that quantitative blood oxygen level dependent (qBOLD) magnetic resonance imaging (MRI)-derived levels of oxygen saturation (SO2) can be used as a surrogate to map oxygen tension in patients with glioblastoma. We investigated whether qBOLD MRI was also able to differentiate different grades of gliomas.
Patients and Methods:
10 patients were enrolled into this prospective study. All patients underwent a preoperative MRI with Ferumoxytol as a contrast agent. Two volumes of interest from the tumor were chosen for biopsy, from sites with different levels of hypoxia. These samples were stained with histological markers and graded by neuropathologists through consensus on a 0-3 scale. Patients with glioblastoma were compared with lower- grade gliomas. Scores were assessed for significant differences using Wilcoxon Two-Sample Test.
In total, 6 patients had pathological GBM; 1 patient had diffuse astrocytoma; and 3 patients had anaplastic astrocytoma. 1 patient a low-grade glioma had an inconclusive biopsy and was therefore excluded from the study. Although VOIs with different levels of SO2 were chosen, SO2 of VOIs did not differ, and histological markers were not significantly different within high-SO2 VOIs. However, within low-SO2 areas GBM showed significantly higher levels of CAIX (p=0.02), and nearly for VEGF (P=0.08). HIF1a staining did not differ (P=0.13). Conclusions:
Advanced qBOLD MRI can potentially differentiate high-grade from low-grade glioma.