Adoption of the T2-FLAIR Mismatch Sign Among Radiologists: How Well Are We Doing?

Background And Purpose: The classic T2-FLAIR mismatch sign is a highly specific MRI feature that can aid in preoperative diagnosis of IDH-mutant 1p/19q noncodeleted gliomas and affect surgical planning. This study aimed to assess the real-world utilization of the T2-FLAIR mismatch sign in clinical practice, and to explore the frequencies of classic-and partial T2-FLAIR mismatch within the IDH-mutant 1p/19q noncodeleted glioma population stratified by tumor grade.

Materials And Methods: This retrospective cohort study from a dedicated cancer referral center included 251 patients with IDH-mutant astrocytoma diagnosed between 2017 and 2022. Pathology reports were reviewed for eligibility for the WHO 2021 diagnostic criteria. Preoperative MR imaging studies were analyzed by two neuroradiologists for the mismatch and enhancement status. MRI reports were assessed for mismatch status reporting frequency, and neuroradiology fellowship status of the dictating radiologist.

Results: 286 preoperative MRIs (212 from outside facilities and 74 in-house) were available from 251 patients with 251 tumors. Of these, 22.3% exhibited classic T2-FLAIR mismatch, 29.8% partial mismatch, and 47.8% no mismatch. Mismatch status significantly differed between WHO grades 2 and 4, but not between grades 2 and 3. Male sex was significantly associated with higher grade. Radiologist reporting rates for the classic mismatch sign were low overall (21.6%), but higher for the dedicated cancer center category (43.3%) compared to other hospital categories (0-10.3%). The reporting rate was also significantly higher for radiologists with neuroradiology fellowship training compared to those without (25.0% vs 0.0%). A statistically significant upward trend in the reporting rate was observed over the years.

Conclusions: The T2-FLAIR mismatch sign is underutilized, particularly in institutions that are not specialized cancer centers. Raising awareness of the T2-FLAIR mismatch sign could enhance preoperative diagnosis of IDH-mutant astrocytoma. Additionally, while the classic mismatch sign is more common in lower-grade IDH-mutant gliomas, it remains relevant in higher-grade tumors.

Abbreviations: IDH = Isocitrate dehydrogenase; WHO = World Health Organization.