P16.01 Surgery for recurrent high grade glioma after treatment with bevacizumab

Abstract

AbstractBevacizumab is a monoclonal antibody to vascular endothelial growth factor (VEGF) which is FDA-approved for the treatment of recurrent glioblastoma. There is some evidence for bevacizumab inducing a treatment-resistant tumor phenotype, by selecting for more infiltrative cells which can subsist without angiogenesis through mechanisms such as cooption of existing blood vessels. Genomic changes may be induced by treatment with bevacizumab, which promote invasion and resistance. While a fraction of recurrent high grade gliomas may be amenable to re-resection, this number is further reduced following treatment with bevacizumab, for several reasons: one, that the tumor is often at an advanced stage after failing bevacizumab, and the patient’s performance status may not be amenable to surgical intervention; two, the tumor may have progressed to a more diffuse and infiltrative phenotype; and three, bevacizumab treatment may increase surgical risks of infections and wound complications, as anti-angiogenic drugs can interfere with the process of wound healing and lead to dehiscence. We report a series of 15 patients, 6 female and 9 male, who underwent tumor resection for recurrent high grade glioma at our center, following progression on bevacizumab treatment. The cohort consists of 12 primary glioblastomas (including one gliosarcoma); 2 secondary glioblastomas transformed from lower grade gliomas; and one anaplastic oligodendroglioma. The mean age of patients was 40 (18-73). Patients were treated with an average of 1.8 therapy lines for recurrent/progressive tumor (including re-operation) before receiving bevacizumab. Median overall survival from time of tumor diagnosis was 21.8 months (7.6-82.0) and median survival from post-bevacizumab surgery was 4.9 months (1.1-19.1). Post-surgical complications included 3 incidences of hemorrhage requiring surgical evacuation and 3 incidences of wound dehiscence or infection, requiring intervention. We did not see overt changes in histopathology or tumor vasculature in tumors resected after treatment with bevacizumab, compared to original samples at diagnosis. We will present detailed data on complications, imaging, and histopathologic findings, comparing pre-bevacizumab to post- bevacizumab samples.