High-field intraoperative MRI in glioma surgery: A prospective study with volumetric analysis of extent of resection and functional outcome

Background: High-field intraoperative MRI (IoMRI) is a useful tool to improve the extent of glioma resection (EOR).

Objective: To compare the interest of 1.5T IoMRI in glioma surgery between enhancing and non-enhancing tumors, based on volumetric analysis.

Methods: A prospective single-center study included consecutive adult patients undergoing glioma surgery with IoMRI. Volumetric evaluation was based on FLAIR hypersignal after gadolinium injection in non-enhancing tumors and T1 hypersignal after gadolinium injection in enhancing tumors. Endpoints comprised: residual tumor volume (RTV), EOR, workflow and clinical outcome on Karnofsky performance score (KPS).

Results: Fifty-three surgeries were performed from July 2014 to January 2016. Thirty-four patients underwent one IoMRI, and 19 two IoMRIs. In non-enhancing tumors, intraoperative RTV on 1st IoMRI T2/FLAIR was higher than in enhancing tumors on T1 sequences (7.25cm³ vs. 0.74cm³, respectively; P=0.008), whereas the RTV on 2nd IoMRIs and final RTV were no longer significantly different. After IoMRI, 72% of patients underwent additional resection. In non-enhancing tumors, EOR increased from 77.3% on 1st IoMRI to 97.4% on last MRI (P<0.001). Taking all tumors together, final RTV values were: median=0cm³, mean=3.9cm³. Mean final EOR was 94%. In 25% of patients, KPS was reduced during early postoperative course; at 3 and 6 months postoperatively, median KPS was 90.

Conclusion: Intraoperative MRI guidance significantly enhanced the extent of glioma resection, especially for non- or minimally enhancing tumors, while preserving patient autonomy.