NIMG-35. IMPACT OF RESECTION AT TIME OF FIRST RECURRENCE IN WHO GRADE 2 IDH-MUTANT GLIOMAS

Abstract INTRODUCTION Maximal safe resection standard of care treatment of IDH-mutant gliomas and is associated with improved overall survival (OS). However, the impact of extent of resection (EOR) at first recurrence is not well established and there are no data on its impact on prognosis. METHODS We retrospectively collected clinical data on patients with IDH-mutant WHO grade 2 astrocytoma and oligodendroglioma treated at our institution from 1997 to 2023. To assess the impact of EOR at first recurrence, we excluded patients who exclusively underwent diagnostic biopsy. Dates of progression were determined by the treating neuro-oncologist or tumor board consensus. Volumetric measurements of contrast-enhancing (CE) tumor and total T2/FLAIR pre- and post second surgery were obtained with BrainLab SmartBrush tool. RESULTS One-hundred patients with recurrent astrocytoma and 35 patients with recurrent oligodendroglioma were identified, of whom 57 and 25, respectively, underwent a second resection and had imaging available for volumetric analysis. In patients with astrocytoma, 13/57 had CE at diagnosis, and 28/57 at first recurrence. EOR of T2/FLAIR and CE volume correlated with improved OS. In multivariate regression analyses, T2/FLAIR EOR at first recurrence correlated with improved OS adjusted for gender, preoperative T2/FLAIR volume, prior radiotherapy or chemotherapy, and initial CE (HR 0.977, p< 0.001). In patients with CE, contrast-EOR correlated with OS adjusted for gender, initial CE, preoperative contrast volume, and prior radiotherapy or chemotherapy (HR 0.929, p< 0.001). Conversely, in patients with WHO grade 2 oligodendroglioma, T2/FLAIR EOR did not significantly impact OS (EOR> 90% p= 0.92, EOR> 20% p= 0.13). Only 5/25 patients had CE at first recurrence precluding further analysis. CONCLUSIONS The EOR of CE and total FLAIR hyperintensity at first recurrence appears to positively impact prognosis in patients with WHO grade 2 astrocytoma but not in oligodendroglioma. These findings should be evaluated in prospective trials.