Effect of bevacizumab on refractory meningiomas: 3D volumetric growth rate versus response assessment in neuro-oncology criteria.

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Meningiomas are the most common primary tumor in the central nervous system. About 15%-20% are aggressive and tend to recur and progress despite conventional treatment. Bevacizumab has been found to be effective in the treatment of refractory meningiomas in retrospective studies. The Response Assessment in Neuro-Oncology (RANO) criteria are widely used to assess the effect of treatment. Recent studies suggest that the 3D volumetric growth rate (3DVGR) may be more accurate for irregularly shaped tumors. The aim of this study was to compare these approaches. Twenty patients with refractory meningiomas were treated with bevacizumab. Tumors were measured using the RANO criteria and 3DVGR before and after initiation of treatment by 2 radiologists using PACS and BRAIN LAB iPLAN software, respectively, findings were compared. A total of 46 lesions were included in the final analysis. Bevacizumab was shown to be effective by both assessment methods. According to RANO criteria, the rate of progression-free survival at 6 months was 47%. According to 3DVGR, all lesions were characterized by either a decrease in volume or stable growth after treatment initiation. A decrease in 3DVGR of 50% or more was found in 90% of lesions. In several patients, there were discordances between RANO criteria and 3DVGR. Although RANO criteria are widely accepted for evaluation of response to treatment of meningiomas, 3DVGR seems to generate more precise measurements of irregularly shaped tumors. The results of this study offer important evidence that bevacizumab may be beneficial in treating refractory meningiomas.