Introduction: Insular gliomas are challenging tumors to surgically resect due to the anatomy surrounding them. This study evaluates the role of extent of resection(EOR) and molecular markers on surgical outcome and survival for insular gliomas.

Methods: Seventy-four patients who had undergone an initial resection for an insular glioma by the same surgeon from 2006 to 2016 were analyzed. Low(grade II) and high(grade III/IV) grade gliomas were analyzed for the prognostic role of volumetric EOR and molecular markers (IDH1 mutation, 1p/19q codeletion) on patient survival outcomes.

Results: The cohort includes 25 low grade gliomas (LGGs) patients(33.8%), and 49 high grade glioma(HGGs) patients(66.2%). The median EOR was 91.7%(range 10-100%). New permanent postoperative deficits were found in 2.7% of patients. LGG patients with a =90% EOR had a 5-year survival rate of 100% and patients with a <90% EOR had 5-year survival of 80%. HGG patients with a =90% EOR had a 2-year survival rate of 83.7%, and patients with a <90% EOR had 2-year survival of 43.8%. For LGGs, accounting for EOR, IDH1 mut, 1p/19 codeletion, the EOR was predictive of OS(p=0.017), progression free survival(PFS, p=0.039), and malignant progression free survival(MPFS, p=0.014), while the 1p/19q co-deletion was predictive for PFS(p=0.014). For HGGs, the EOR was predictive of OS(p=0.020) and PFS(p=0.024). Preoperative tumor volume was a factor that most significantly affected the EOR for insular gliomas(R2=0.053,p=0.048).

Conclusions: Extensive resections of insular gliomas can be achieved with low morbidity and can improve OS and PFS. In this series of low-grade gliomas, EOR was associated with longer MPFS, and the 1p/19q co-deletion was predictive of PFS.

Patient Care: This research presents the first extent of resection analysis for insular gliomas that accounts for molecular markers. This allows surgeons to determine a better prognosis for patients with insular gliomas based on EOR and molecular markers.

Learning Objectives: By the conclusion of this session, participants should be able to: 1)Describe the importance of extent of resection for insular gliomas, 2) Understand the prognostic implications of molecular markers for insular gliomas and their role with extent of resection

References: 1. Duffau H, Capelle L. Preferential brain locations of low-grade gliomas. Cancer. 2004;100(12):2622-2626. 2.Hervey-Jumper SL, Li J, Osorio JA, et al. Surgical assessment of the insula. part 2: Validation of the berger-sanai zone classification system for predicting extent of glioma resection. J Neurosurg. 2016;124(2):482-488. 3. Wang Y, Wang Y, Fan X, et al. Putamen involvement and survival outcomes in patients with insular low-grade gliomas. J Neurosurg. 2016:1-7. 4. Simon M, Neuloh G, von Lehe M, Meyer B, Schramm J. Insular gliomas: The case for surgical management. J Neurosurg. 2009;110(4):685-695.