- We now propose treating patients whose tumors progress on our bevacizumab alone protocol with the combination of bevacizumab with irinotecan. We believe that this trial design has significant power to detect a true synergistic effect between the two agents given that the single agent activity of irinotecan is so low in patients with recurrent malignant gliomas (2-5% response rate) and the patients being treated on this trial will have tumors that have already progressed through bevacizumab.