Maximum Resection of Noncontrast-enhanced Tumor at MRI Is a Favorable Prognostic Factor in IDH Wild-Type Glioblastoma

Background Isocitrate dehydrogenase (IDH) wild-type glioblastoma often includes a noncontrast-enhanced tumor (NET) component, and the extent of NET resection may serve as a prognostic marker. Purpose To assess clinical outcomes based on gross total resection (GTR) of NET, develop a real-world survival model incorporating GTR-NET for IDH wild-type glioblastoma, and validate the findings in multinational external cohorts. Materials and Methods A retrospective analysis included patients with IDH wild-type glioblastoma in a prospective registry (March 2017 to October 2020) as the training set. External validation used consecutive patients from two centers (March 2017 to January 2023). Patients were stratified into three groups: GTR-NET, GTR in contrast-enhanced tumor (CET) only, and no GTR. A conditional inference tree (CIT) model was developed using GTR type, age, and O⁶-methylguanine DNA methyltransferase (<i>MGMT</i>) promoter methylation status to predict overall survival (OS) and was externally validated. Kaplan-Meier analysis, log-rank test, time-dependent area under the receiver operating characteristic curve, and Harrell C-indexes were used for evaluation. Results In the training set (<i>n</i> = 201; mean age, 60 years ± 11.3; 109 males), four survival groups were identified. GTR-NET was associated with longer OS (median, 32.6 months; IQR, 18.7-46.7 months; <i>P</i> < .001). When GTR-NET was not achieved, OS was stratified as follows: younger than age 60 years (median OS, 23.4 months; IQR, 12.2-34.8 months), age 60 years or older and positive for <i>MGMT</i> (median OS, 19.1 months; IQR, 13.0-27.8 months), and age 60 years or older and negative for <i>MGMT</i> (median OS, 10.7 months; IQR, 6.5-14.1 months). External validation sets (352 patients in external validation set 1 and 60 patients external validation set 2) confirmed these groups (<i>P</i> < .001 and <i>P</i> = .04). Time-dependent areas under the receiver operating characteristic curve ranged from 0.684 (95% CI: 0.623, 0.745) to 0.694 (95% CI: 0.631, 0.758) and from 0.610 (95% CI: 0.449, 0.771) to 0.678 (95% CI: 0.512, 0.844), with CIT sensitivity for GTR-NET at 70.7%-77.3% and 87.6%-87.9% and C-indexes of 0.65 and 0.63. Conclusion A GTR-NET-based survival model was developed and validated, demonstrating that GTR-NET is an independent prognostic marker for longer OS in IDH-wildtype glioblastoma. ClinicalTrials.gov identifier: NCT02619890 © RSNA, 2025 <i>Supplemental material is available for this article.</i>