Extent of Resection and Survival in IDH-Wildtype Glioblastoma: A Dual-Center Retrospective Study

Background and Objectives: Glioblastoma (GBM), defined as IDH-wildtype CNS WHO grade 4, remains the most common and aggressive primary malignant brain tumor in adults. Although the extent of resection (EOR), particularly gross total resection (GTR), is considered a potentially modifiable factor, survival comparisons across surgical groups are vulnerable to selection bias and unmeasured biological confounding. We evaluated the association between GTR and survival outcomes in patients with newly diagnosed IDH-wildtype GBM in a dual-center, real-world cohort. Materials and Methods: We conducted a retrospective, dual-center cohort study of 100 adult patients with histopathologically confirmed GBM who underwent primary surgical resection between 2015 and 2021. GTR was defined as no measurable residual contrast-enhancing tumor on early postoperative MRI (≤72 h). All patients received adjuvant chemoradiotherapy according to the Stupp protocol. Survival was analyzed using Kaplan-Meier methods with log-rank tests and explored using univariable Cox regression analysis. Given the missing key prognostic covariates (notably MGMT promoter methylation) and the retrospective design, the analyses were reported as unadjusted and descriptive. Results: Of the 100 patients, 63 (63%) underwent GTR and 37 (37%) non-GTR. The GTR group had a significantly higher rate of radiologic complete response (42.9% vs. 10.8%, p = 0.001). However, no significant differences were observed in overall survival (OS; median 13 vs. 12 months, p = 0.847) or progression-free survival (PFS; 8 vs. 8 months, p = 0.963) between the groups in unadjusted analyses. Long-term Kaplan-Meier estimates (e.g., 5-year OS) should be interpreted cautiously due to the small number of patients at risk and potential selection and biological confounding. Conclusions: In this dual-center cohort, GTR was associated with improved radiologic response but not with longer OS or PFS in unadjusted analyses. These results should be considered hypothesis-generating and not interpreted as evidence against maximal safe resection. The absence of MGMT promoter methylation status, lack of volumetric EOR quantification (including non-contrast-enhancing/FLAIR disease), and lack of standardized functional outcome data substantially limited causal inference. Prospective studies integrating molecular stratification, volumetric resection metrics, and functional outcome assessments are warranted.