Calcification in high grade gliomas treated with bevacizumab

Calcification is a rare phenomenon in high grade glioma (HGG). CT scans are sensitive to mineralization but used infrequently for tumor assessment in the MRI era. The presence of calcification can be overlooked on routine MRI. Calcification may reflect chronicity and natural changes in the tumor or its milieu over time and may be accelerated by certain treatments. Calcification may have clinical significance which could signal potential risk for stroke or hemorrhage related to particular therapies; or it may be a positive prognostic factor for treatment response. The true incidence and relevance of calcification in HGG and relation to therapy is unclear. During treatment of HGG patients with bevacizumab (BVZ) we observed significant tumor calcification on brain CT. We performed a retrospective review of HGG patients treated with BVZ to quantitate the incidence of calcification in this group compared to those treated with cytotoxic therapy alone. Sixty-two patients with progressive HGG were treated with BVZ and a cytotoxic agent. Among 19 patients treated for 6+ months, 12 had a CT scan performed. We observed an unexpected phenomenon of calcification in the CT scans of several patients. We were also able to comparatively quantitate the incidence of calcification in a control group of primary glioblastoma (GB) patients not exposed to BVZ therapy. The incidence of calcification in the general GB population is increased with longer survival. The phenomenon is increased with anti-angiogenic therapy for brain tumors. Calcification may have significance as a predictor for treatment response.