TIP-18. The Dural Tail in Meningiomas: Correlation of MRI, PET, and neuropathological findings

BACKGROUND The dural tail sign on MRI is commonly interpreted as tumor infiltration in meningiomas, though histology confirms infiltration in only ~50% of cases, suggesting possible reactive changes. Somatostatin receptor PET is more sensitive than MRI in distinguishing tumor from non-tumor tissue, but its role in assessing the dural tail remains unclear. This interim analysis of a prospective study correlates MRI and PET/CT findings with histopathology. METHODS Patients >18 years with newly diagnosed meningioma and MRI-visible dural tail (01/2023–12/2024) were screened. Only PET-positive tumors on preoperative SIFATATE-PET/CT were included. A neuroradiologist labeled the dural tail; biopsy targets (PET+MRI+, PET–MRI+, PET–MRI–) were selected jointly on fused images. No PET+MRI– sites were observed. Navigated intraoperative samples were taken. Imaging findings were correlated with histology. DNA methylome and Maas et al. risk scores (MS) were assessed only in the main tumor. RESULTS 20 patients (15 female; mean age 59.9±10.8 years) were analyzed. Histology revealed 2 WHO grade 2 (MS 5 and 1) and 18 WHO grade 1 meningiomas (MS 2 in 4, MS 0 in 8, n/a in 6). Biopsies were taken at average distances of 6.0 mm (PET+MRI+), 11.2 mm (PET–MRI+), and 15.5 mm (PET–MRI–). Tumor infiltration was found in 80% of PET+MRI+, 45% of PET–MRI+, and 15% of PET–MRI– samples. Tumor infiltration significantly correlated with distance from the main tumor (p = 0.035). No correlation was found with WHO grade, MS score, age, or sex. MRI-positive dural tail showed a sensitivity/specificity of 89.2%/50.5%, PET-positive 57.1%/86.7%, and congruent PET/MRI results 84.2%/79.0%. CONCLUSION MRI-PET combination shows higher predictive accuracy for dural tail infiltration than MRI alone. Final results are pending as recruitment continues.