The efficacy of
bevacizumab has not been determined for treatment-refractory
meningiomas. We treated
meningiomas with low-dose
bevacizumab and compared the radiological responses of non-irradiated
meningiomas with previously irradiated
meningiomas. In addition, we assessed intraparenchymal radiation
necrosis following
bevacizumab treatment.Six patients with
meningiomas (three anaplastic, one atypical, and two grade I) who were previously treated with multiple sessions of
radiotherapy and subsequently developed perilesional
edema were treated with
bevacizumab. Of six patients, two patients with anaplastic
meningiomas developed three
tumors following
radiotherapy, which were defined as non-irradiated
tumors. There were 12 pre-existing extra-axial
tumors that were previously irradiated. Some of these
tumors demonstrated adjacent intraparenchymal contrast enhancement. These
tumors were defined as post-irradiated
tumors. Four patients had intraparenchymal radiation
necrosis. Low-dose
bevacizumab was administered biweekly over 3-6 cycles to all patients.Four
tumors decreased in contrast-enhanced volume, nine
tumors were unchanged, and two
tumors progressed. Of the three non-irradiated
tumors, two
tumors increased in volume (126 % and 198 %) and one
tumor was stable (-5 %). The median reduction rates determined by contrast volume were -31 % and -71 % in post-irradiated
tumors and radiation
necrosis, respectively. Non-irradiated
tumors had a significantly poorer response to
bevacizumab than post-irradiated
tumors and radiation
necrosis (p = 0.0013 and p = 0.0005, respectively, Tukey-Kramer test).Low-dose
bevacizumab did not demonstrate efficacy in the treatment of non-irradiated
meningiomas. Responses to low-dose
bevacizumab could be related to its effect on post-irradiation changes, rather than its effect on biologically active
tumor tissue in post-irradiated
meningiomas. Radiological responses to low-dose
bevacizumab may distinguish biologically active
tumors from post-irradiation changes in progressive
meningiomas following
radiotherapy.