T2/FLAIR Mismatch Subregion as an Independent Prognostic Biomarker in IDH-Mutant and 1p/19q Noncodeletion Astrocytoma

BACKGROUND AND PURPOSE: While the global T2/FLAIR mismatch sign is a diagnostic hallmark of IDH-mutant and 1p/19q noncodeletion astrocytoma, the prognostic significance of partial mismatch patterns remains unclear. This study investigated the differences in MRI between subregions with a T2/FLAIR mismatch and a match, and the impact of these differences on astrocytoma clinical outcomes. MATERIALS AND METHODS: This retrospective study analyzed 221 patients with histopathologically confirmed IDH-mutant and 1p/19q non-codeletion astrocytoma, stratified by the presence (n=131) or absence (n=90) of T2/FLAIR mismatch subregions. Clinical data, morphological MRI features, and molecular profiles were compared. Quantitative apparent diffusion coefficient (ADC) and relative cerebral blood volume (rCBV) measurements were obtained from mismatch (n=131) and match (n=178) subregions. Univariate and multivariate Cox regression identified prognostic factors for progression-free survival (PFS) and overall survival (OS). RESULTS: Patients with mismatch subregions were younger, had lower WHO grades, higher gross total resection rates, lower Ki-67 labeling index, and lower incidences of necrosis, cystic degeneration, peritumoral edema, and contrast enhancement (all p < 0.05). Mismatch subregion exhibited significantly higher ADC and lower rCBV than match subregions (p < 0.001). Multivariate analysis confirmed that peritumoral edema, enhancement, Ki-67 LI, and ATRX were independent predictors of PFS. The mismatch subregion, enhancement, Ki-67 LI and adjuvant chemoradiotherapy were independent predictors of OS. CONCLUSIONS: Significant heterogeneity exists between T2/FLAIR mismatch and match subregions in IDH-mutant and 1p/19q noncodeletion astrocytoma. The presence of a T2/FLAIR mismatch subregion is an independent favorable prognostic factor, correlating with improved OS. ABBREVIATIONS: FLAIR = Fluid Attenuation Inversion Recovery; IDH = isocitrate dehydrogenase; ADC = Apparent diffusion coefficient; rCBV = Relative cerebral blood volume; PFS = progression-free survival; OS = overall survival; mMRI = morphological MRI; DWI = Diffusion-weighted imaging; DSC-PWI = Dynamic susceptibility contrast perfusion-weighted imaging.