Vascular hemodynamic profiles of vestibular schwannomas and glioblastoma using MRI.

Abstract

2047 Background: Bilateral vestibular schwannomas (VS) are the hallmark of neurofibromatosis 2 (NF2), a tumor suppressor syndrome that affects the central nervous system. These benign tumors cause progressive hearing loss and brainstem compression. Current options, including surgery and radiotherapy, can cause hearing loss, facial weakness and dysphagia. Treatment with anti-VEGF antibody improves hearing and reduces tumor volume in the majority of patients. Our aim was to evaluate the angiogenic phenotype of VS compared to glioblastoma (GBM), a malignant tumor that is dependent on new blood vessel formation. Methods: Eleven patients with NF2 and eight patients with GBM were scanned on a 3 Tesla imaging spectrometer. Estimates of Ktrans (a measure of vascular permeability) were derived from dynamic contrast enhanced MRI, apparent diffusion coefficient (ADC, a measure of tissue water content) estimates were derived from diffusion imaging, and relative cerebral blood volume (rCBV, a measure of blood volume) estimates were derived from dynamic susceptibility MRI. The mean values for each parameter were compared for VS and GBM by a Student’s t-test. Results: The mean tumor volume for VS was 11.2 ml (range, 1.4 to 29.1 ml) and for GBM was 24.8 ml (range, 4.5 to 56.3 ml). The mean ADC value was significantly greater in VS than in GBM (1.406 x 10-3 mm2/sec vs. 1.014 x 10-3 mm2/sec; P=0.0001). The mean Ktrans estimate was higher in VS than in GBM (0.068 hour-1 vs. 0.021 hour-1), although this did not reach statistical significance (P=0.106). The mean rCBV value was similar between VS and GBM (2.294 vs. 1.934, P=0.269). Conclusions: Our results suggest that VS have strikingly abnormal vasculature, with features similar to that of GBM. The tumor vasculature is highly permeable and the tumors show increased diffusion of water molecules (eg., radiologic marker of tissue edema). Our preliminary data suggest that histologically benign tumors may have abnormal vessels and that these vessels may contribute to increased tissue edema. Anti-VEGF therapy is a rational approach to treatment of progressive VS through an anti-edema effect. Novel VEGF inhibitors may improve outcomes for this tumor.