SURG-24. MAXIMAL SAFE RESECTION OF INSULAR GLIOMAS: AN EVALUATION OF SURGICAL AND PROGNOSTIC OUTCOMES IN 461 CASES

Abstract INTRODUCTION Insular gliomas are challenging to resect due to nearby functional cortical/subcortical structures and delicate Sylvian/sub-insular vascularity. Motor/language mapping and surgical experience are necessary for maximal safe resection (MSR). METHODS Outcomes were retrospectively evaluated following MSR in the largest single-institution series to date. 461 cases, between 1997 and 2022, were classified according to the Berger-Sanai system. Contrast-enhancing (CETV) and non-contrast-enhancing (nCETV) tumor volumes were calculated manually. RESULTS The final cohort comprised 226 high-grade (IDH-mutant, n=82) and 226 low-grade (IDH-mutant, n=101) tumors. Median nCETV was 47.7ml (grade 2, n=226), 72.6ml (grade 3, n=136), and 46.8ml (grade 4, n=90). Median CETV was 22ml for grade 3 and 13.6ml for grade 4 tumors. Most were classified as Zone I (37%), IV (8.6%), or I+IV (15%). For high-grade tumors, median CE-EOR was 96.1% (range, 29.7-100), which was highest in Zone I (100%), and supra-maximal resection was achieved in 5 cases. For low-grade tumors, median nCE-EOR was 82.4% (range, 28.4-100), which was highest in Zone 4 (85%). Additionally, initial nCETV in low-grade tumors was not associated with nCE-EOR, even when controlling for location. New postoperative motor deficits by discharge were significantly higher in Zones II (24%), I+II (22%), and III (23%). For dominant-hemisphere tumors, language deficits were highest in Zone I+II (44%), Giant (32%), and Zone II+III (29%) tumors. At 3 months, language deficits persisted in Giant (7.1%) tumors and motor deficits persisted in Giant (6.4%) and Zone II (5.9%) tumors. Median overall survival (OS) was 114.6 (grade 2), 108.6 (grade 3), and 14.7 (grade 4) months. In primary high-grade tumors, OS was longer with CE-EOR > 97.1% (36.8 vs.14.7 months, p=.04) and nCE-EOR of > 80.8% (91.3 vs. 20.2 months, p<.001). CONCLUSIONS In a high-volume academic center, surgical resection of insular gliomas with cortical/subcortical mapping can achieve excellent EOR with minimal language and motor morbidity.