Accuracy of the neurosurgeons estimation of extent of resection in glioblastoma

BACKGROUND: The surgeons’ estimate of the extent of resection (EOR) shows little accuracy in previous literature. Considering the developments in surgical techniques of glioblastoma (GBM) treatment, we hypothesize an improvement in this estimation. This study aims to compare the EOR estimated by the neurosurgeon with the EOR determined using volumetric analysis on the post-operative MR scan. METHODS: Pre- and post-operative tumor volumes were calculated through semi-automatic volumetric assessment by three observers. Interobserver agreement was measured using intraclass correlation coefficient (ICC). A univariate general linear model was used to study the factors influencing the accuracy of estimation of resection percentage. RESULTS: ICC was high for all three measurements: pre-operative tumor volume was 0.980 (0.969–0.987), post-operative tumor volume 0.974 (0.961–0.984), and EOR 0.947 (0.917–0.967). Estimation of EOR by the surgeon showed moderate accuracy and agreement. Multivariable analysis showed a statistically significant effect of operating neurosurgeon (p = 0.01), use of fluorescence (p < 0.001), and resection percentage (p < 0.001) on the accuracy of the EOR estimation. CONCLUSION: All measurements through semi-automatic volumetric analysis show a high interobserver agreement, suggesting this to be a reliable assessment of EOR. We found a moderate reliability of the surgeons’ estimate of EOR. Therefore, (early) post-operative MRI scanning for evaluation of EOR remains paramount. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00701-019-04089-8) contains supplementary material, which is available to authorized users.