Glioma extent of resection and ultra-low-field iMRI: interim analysis of a prospective randomized trial.

Aiming at providing high-class evidence regarding the use of intraoperative MRI (ioMRI), we are conducting a prospective randomized controlled trial. Adult patients with contrast enhancing lesions suspicious of malignant gliomas scheduled to undergo radiologically complete tumor resection are eligible to enter this trial. After giving their informed consent, patients are randomized to undergo either ioMRI-guided or conventional microneurosurgical tumor resection. To assess the extent of resection, pre- and early postoperative high-field MR images are obtained to perform volumetric analyses. Primary endpoint of the study is the rate of radiologically complete tumor resections. After the inclusion of 35 patients, we performed an interim analysis. In six patients, histopathological examination revealed metastases, so they were excluded from further analyses. Thus, data from 29 patients with gliomas could be analyzed. There were no significant differences in patient age (P=0.28) or preoperative tumor sizes (P=0.40) between the two treatment groups. We observed a trend towards a higher rate of complete tumor resections in the ioMRI-group compared to the control group (P=0.07). Postoperative tumor volumes were significantly lower in the ioMRI-group than in the control group (P<0.05). The use of ioMRI appears to be associated with a higher rate of radiographically complete as well as near total tumor resections compared to conventional microneurosurgery.