Abstract General Information

Title

Addition of tumor localization to T2/FLAIR mismatch sign on Magnetic Resonance Imaging (MRI) for improving preoperative prediction of 1p19q codeletion in low-grade gliomas.

Introduction, Objectives, Methods, Results, and Conclusion.

INTRODUCTION
Low-grade gliomas, presenting isocitrate dehydrogenase (IDH) 1 or 2 mutations are considered to be of better prognosis. When co-deletion of chromosomes 1p and 19q is also present, these tumors are classified as oligodendrogliomas and prognosis is improved even further.
Recent studies have shown presence of a T2/FLAIR mismatch sign on MRI can help predict the presence of astrocytomas with IDH mutation, with high specificity but low sensitivity. Other studies have shown temporal lobe location is more frequent in astrocytomas and frontal lobe location in oligodendrogliomas.
Our objective was to evaluate the diagnostic value of adding tumor location to T2/FLAIR discordance to help distinguish IDH-mutated astrocytomas from oligodendrogliomas, in a cohort of adult patients with low-grade gliomas presenting IDH mutation..

MATERIALS AND METHODS
Descriptive retrospective study of 127 adult patients with low-grade glioma and IDH mutation, operated at our institution between 2010 and 2019.
T2-FLAIR mismatch sign was interpreted as present when complete hyperintensity in the T2 sequence was accompanied by hyperintensity suppression on the FLAIR sequence, with the exception of a peripheral hyperintense halo.
Tumor location was defined according to the most affected lobe within the brain on preoperative magnetic resonance images.

RESULTS
In this cohort, T2-FLAIR mismatch sign was associated with diagnosis of astrocytoma (OR = 42.84 [8.04,796.62], p = 0.0003) with a sensitivity of 0.66, a specificity of 0.95 and a PPV (positive predictive value) and NPV (negative predictive value) of 0.95 and 0.68, respectively. Diagnosis of astrocytoma was negatively related to frontal lobe location (OR = 0.44 [0.20,0.92], p = 0.033) and positively related to temporal lobe location (OR = 5.04 [1.77,18.22] p = 0.005) . Multivariate analysis showed sensitivity = 0.75, a specificity = 0.93 and a PPV and NPV of 0.93 and 0.73, respectively.

CONCLUSION
The T2-FLAIR mismatch sign is a useful tool to diagnose astrocytomas with IDH mutation preoperatively with high specificity and low sensitivity. Adding tumor localization to imaging findings increases sensitivity.
Using features easy to observe on conventional MRI, 1p19q codeletion status in IDH-mutated tumors can be predicted with considerable precision.

Keywords (separated by comma on a single line)

KEYWORDS
Low grade glioma, T2/FLAIR mismatch sign, MRI, oligodendroglioma, astrocytoma.