P15.05.b the impact of iomri on glioblastoma resection and clinical outcomes in a state-of-the-art neuro-oncological setup

BACKGROUND Intraoperative magnetic resonance imaging (ioMRI) is applied to improve the extent of resection in patients suffering from primary brain tumors, especially glioblastoma (GBM). While some older randomized trials reported data on safety and feasibility, ioMRI’s actual impact in a modern neurosurgical setting has not been sufficiently investigated. We therefore aimed to evaluate the effect of ioMRI on tumor resection and progression-free survival (PFS) in GBM patients in a modern high-volume center. MATERIAL AND METHODS Patients undergoing ioMRI for resection of supratentorial GBM were prospectively included between March 2018 and June 2020. In all cases, ioMRI was performed after complete macroscopic tumor resection. The extent of resection (EOR) was determined by volumetric analysis. Gross total resection (GTR) was defined as EOR ≥95%. Furthermore, progression-free survival (PFS) was analyzed through univariate and multivariate Cox proportional regression analysis. RESULTS Overall, 172 patients were enrolled in this study. The mean EOR increased from 93·9% on ioMRI to 98·3% (p<0·0001) on postoperative MRI, with residual tumor volume decreasing from 1·3 ± 4·2 cm3 to 0·6 ± 2·5 cm3(p=0·0037). The GTR rate increased from 78·5% to 93·0% (p=0·0002). Logistic regression revealed recurrent GBM (odds ratio [OR] =3·047, 95% confidence interval [CI] 1·165-7·974, p=0·023) and tumor volume less than 15 cm3 (OR=3·031, 95% CI 1·062-8·651, p=0·038) as independent risk factors leading to STR. Tumor resection performed additionally after ioMRI lead to equally long PFS compared to patients with complete tumor removal achieved before ioMRI (HR=0·898, 95%CI 0·543-1·483, p=0·67). CONCLUSION ioMRI serves as a valuable tool in a modern neurosurgical setting, severely decreasing residual tumor volume. ioMRI considerably helps to achieve comparable PFS even in cases, where an unexpected tumor residual is found on ioMRI after initial resection.