Post-Treatment MRI Features on First Follow-Up Imaging in Diffuse Gliomas After Near-Total Resection: A Real-World Exploratory Cohort Study

Background and Objectives: Magnetic resonance imaging (MRI) is essential for monitoring patients with diffuse gliomas after surgery and adjuvant therapy. However, the prognostic significance of imaging findings observed on the first post-treatment MRI remains incompletely defined in routine clinical practice. This study aimed to evaluate whether MRI features identified on the first post-treatment examination are associated with recurrence-free survival after near-total resection (NTR), defined for this real-world cohort as ≥80% volumetric tumor removal (which differs from the RANO Resect Group definition of GTR). Materials and Methods: Consecutive adult patients with histologically confirmed diffuse gliomas diagnosed between 2021 and 2024 were screened for eligibility (n = 283) and classified according to the 2021 WHO Classification of Tumors of the Central Nervous System. The first post-treatment MRI was defined as the earliest follow-up examination performed after completion of all initially planned therapy (surgery alone in patients without indication for adjuvant therapy; post-radiotherapy ± chemotherapy in the remaining patients), and not the immediate postoperative scan. Patients with available first post-treatment MRI were included (n = 149), resulting in a final cohort of 139 cases after exclusion of outliers. The evaluated MRI corresponded to the first follow-up examination after treatment (mean interval ~120 days after surgery). Logistic regression models were used to assess associations between post-treatment MRI features and recurrence-free survival at one and two years after NTR, with exploratory analyses for reoperation and reirradiation. Results: Residual tumor identified on the first post-treatment MRI was associated with lower odds of recurrence-free survival (RFS) at one and two years after NTR. Postoperative functional status also demonstrated an independent association with tumor control. Other imaging variables showed associations in univariable analyses but did not remain independent predictors after adjustment. Exploratory analyses of reoperation and reirradiation suggested additional clinical influences, including patient age. Conclusions: In this real-world cohort with heterogeneous tumor subtypes and treatment regimens, residual tumor on first follow-up MRI was the most consistent imaging correlate of reduced RFS, alongside postoperative functional status. These hypothesis-generating findings should be validated in stratified, prospective cohorts.