Extent of resection and survival in <i>IDH</i> -mutant WHO grade 2 glioma: A systematic review and meta-analysis.

e14098 Background: For IDH-mutant WHO grade 2 gliomas, extent of resection (EOR) is thought to improve long-term outcomes, but optimal thresholds and survival benefit remain uncertain. Quantifying the impact of EOR can guide surgical planning and patient counseling. Methods: We performed a systematic review and meta-analysis of MEDLINE, Embase, CENTRAL, and Web of Science. Eligible studies reported EOR (continuous or categorical) and outcomes including overall survival (OS), progression-free survival (PFS), malignant transformation, seizure control, and treatment-related morbidity. Random-effects models pooled hazard ratios (HRs) for survival outcomes, and meta-regression assessed relationships between EOR, histologic subtype (astrocytoma vs oligodendroglioma), measurement method (MRI volumetrics vs surgeon estimate), and adjuvant therapy. Results: Twelve studies including 1,052 patients were analyzed. Higher EOR was associated with improved survival: pooled HR for OS per 10% incremental resection was 0.88 (95% CI 0.83–0.93), and for PFS 0.85 (95% CI 0.79–0.91). Patients achieving ≥90% resection had the greatest benefit, with 10-year OS of 88% versus 62% for &lt;90% resection (p &lt; 0.001). Higher EOR also reduced risk of malignant transformation (HR 0.67, 95% CI 0.53–0.85) and improved seizure control in 68% of evaluable patients. Results were consistent across histologic subtypes and measurement methods, with minimal heterogeneity (I² &lt; 35%). Conclusions: Greater EOR in IDH-mutant grade 2 gliomas is strongly associated with improved survival, lower malignant transformation risk, and better seizure control, supporting maximal safe resection as the standard of care. Clinical takeaway: Surgical planning aiming for ≥90% resection can optimize long-term outcomes and quality of life in patients with IDH-mutant grade 2 gliomas.