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 isocitrate dehydrogenase (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 World Health Organization (WHO) 2021 diagnostic criteria. Preoperative MR imaging studies were analyzed by 2 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: Two hundred eighty-six 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 with other hospital categories (0%–10.3%). The reporting rate was also significantly higher for radiologists with neuroradiology fellowship training compared with those without (25.0% versus 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.