Introduction: There is ample evidence that extent of resection (EOR) is associated with survival for intracranial glioma surgery. However, it is often difficult to accurately estimate intraoperative EOR, and surgeon accuracy has yet to be reviewed. In this study, we quantitatively assess the accuracy of intraoperative perception of EOR.

Methods: A single surgeon experience of awake craniotomies for tumor resection over a 17-year period was examined. Retrospective review of operative reports for quantitative estimation of EOR was recorded. Definitive EOR were based on postoperative MRI. Analysis of accuracy was examined (a) as a general outcome (gross total resection (GTR) or subtotal resection (STR)) and (b) quantitatively (5% within postoperative MRI). Patient and tumor characteristics were also examined.

Results: A total of 476 patients had sufficient data and were included. Overall accuracy of intraoperative perception of whether GTR or STR was achieved was 80.2%. There was a significant improvement in the perception of intraoperative EOR over a 17 year period: 70.0% accuracy at year 1 with improvement to 100.0% accuracy at year 17 (p=0.031). In regards to intraoperative quantitative perception of resection (perception of EOR within 5% of postoperative MRI), overall accuracy was 82.1%. Similarly, there was a significant improvement in accuracy of quantitative perception of EOR over the 17 years: from 66.7% correct at year 1 to 100.0% correct at year 17 (p=0.026). Location was an important factor in influencing perceiving EOR; insular tumors were significantly associated with lower accuracy of estimating quantitative intraoperative EOR (61.5% correct, p<0.001). Grade, recurrence, diagnosis, IDH1 status, and 1p19q status were not associated with perception of EOR.

Conclusions: The findings from this study suggests that there is a learning curve associated with being able to accurately assess intraoperative EOR during glioma surgery, and it may take over a decade to be truly proficient.

Patient Care: Understanding the factors and learning curve associated with being able to accurately assess extent of tumor resection will provide safer surgeries while providing adequate tumor resection. This in turn will translate to improved morbidity and survival for patients with gliomas.

Learning Objectives: By the conclusion of this session, participants should be able to: 1. Understand the importance of surgical experience associated with predicting extent of resection. 2. Describe techniques that may help achieve better prediction of extent of resection. 3. Understand that tumor location influences the ability to estimate extent of resection.

References: 1. Sanai N, Polley MY, McDermott MW, Parsa AT, Berger MS. An extent of resection threshold for newly diagnosed glioblastomas. J Neurosurg. 2011 Jul;115(1):3-8. 2. Sanai N, Berger MS. Extent of resection influences outcomes for patients with gliomas. Rev Neurol (Paris). 2011 Oct;167(10):648-54. 3. Orringer D, Lau D, Khatri S, Zamora-Berridi GJ, Zhang K, Wu C, Chaudhary N, Sagher O. Extent of resection in patients with glioblastoma: limiting factors, perception of resectability, and effect on survival. J Neurosurg. 2012 Nov;117(5):851-9.