Circulating endothelial cells and progenitors in recurrent high-grade gliomas treated with bevacizumab and irinotecan

2044 Background: Bevacizumab (Bev), a monoclonal antibody targeting the vascular endothelial growth factor (VEGF), has shown significant activity in a subset of patients with high grade gliomas (HGG): to date no biological marker can predict the treatment benefit. Circulating endothelial cells (CEC) and progenitors (CEP) have been observed in cancer patients, reflecting ongoing tumor angiogenesis. Methods: Forty-seven HGG patients (38 glioblastoma, GB; 9 anaplastic astrocytomas), relapsing after radiotherapy and temozolomide, were treated every 2 weeks with Bev (10 mg/kg) and irinotecan (125 or 340 mg/m2 depending on EIAEDs use). Adverse events were graded based on the CTC-AE v3.0. Before first treatment and every 8 weeks MRI and CEC and CEP assessment were performed. Radiological responses were assessed based on RANO criteria. CEC and CEP were enumerated in healthy controls (n=37) and patients by six color flow cytometry as Syto+CD45-CD31+/P1h12+ and Syto+CD45-CD31+/CD133+ cells, respectively. The Kaplan...