Volumetric Analysis of Extent of Resection, Survival, and Surgical Outcomes for Insular Gliomas

Background Insular gliomas are challenging tumors to surgically resect owing to the anatomy surrounding them. This study evaluates the role of extent of resection (EOR) and molecular markers in surgical outcome and survival for insular gliomas. Methods Seventy-four patients who had undergone initial resection for insular glioma by the same surgeon between 2006 and 2016 were analyzed. Low-grade gliomas (LGGs) (grade II) and high-grade gliomas (HGGs) (grade III/IV) were analyzed for the prognostic role of volumetric EOR and molecular markers in patient survival outcomes. Results The cohort included 25 patients with LGGs (33.8%) and 49 patients with HGGs (66.2%). Median EOR was 91.7% (range, 10%–100%). New permanent postoperative deficits were found in 2.7% of patients. Patients with LGGs with ≥90% EOR had 5-year survival of 100%, and patients with <90% EOR had 5-year survival of 80%. Patients with HGGs with ≥90% EOR had 2-year survival of 83.7%, and patients with <90% EOR had 2-year survival of 43.8%. For LGGs, EOR was predictive of overall survival (P = 0.017), progression-free survival (PFS) (P = 0.039), and malignant PFS (P = 0.014), whereas 1p/19q codeletion was predictive of PFS (P = 0.014). For HGGs, EOR was predictive of overall survival (P = 0.020) and PFS (P = 0.024). Preoperative tumor volume most significantly affected 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 overall survival and PFS. In this series of LGGs, EOR was associated with longer malignant PFS, and 1p/19q codeletion was predictive of PFS.