Mechanism and significance of diffusion restriction followed by calcification in high-grade glioma treated with bevacizumab

Abstract

In this study, we focused on calcification and diffusion restriction, which sometimes appear around the resection cavity or periventricular white matter in patients with high-grade glioma (HGG) treated with bevacizumab (BVZ), as candidate imaging biomarkers for BVZ treatment efficacy. We investigated the timing of the appearance of diffusion restriction and calcification using magnetic resonance imaging and computed tomography in 35 patients with newly diagnosed or recurrent HGG treated with BVZ. In 17 (48.6%) patients, calcification was identified around the resection cavity or periventricular white matter at a median of 12 months after the initiation of BVZ treatment. Patients with calcification had significantly longer progression-free survival (16 vs. 7 months; p = 0.0023) and overall survival (36 vs. 12 months; p = 0.0006) than those without calcification. Histopathological examination revealed the presence of scattered microcalcifications within areas of necrosis, which suggested dystrophic calcification induced by BVZ. Diffusion-restricted lesions that appeared in patients with calcification had significantly lower apparent diffusion coefficients than those in patients without calcifications, indicating the presence of treatment-related necrosis but not hypercellularity. In conclusion, the radiological finding of diffusion restriction followed by calcification could be a potential imaging biomarker for favorable clinical course in patients with HGG treated with BVZ.