Abstract B17: Utility of MRI and PET/CT to differentiate benign versus malignant peripheral nerve sheath tumors (MPNST)

Abstract

Abstract Aim: To assess the utility of MRI and PET/CT to differentiate benign versus malignant peripheral nerve sheath tumors (MPNST). Methods: We retrospectively identified 68 patients with histologically confirmed nerve sheath tumors. All of these patients had pretreatment magnetic resonance imaging (MRI) studies and 17 patients had pretreatment 18-fluorodeoxyglucose positron emission tomography (PET/CT). Age, history of neurofibromatosis, maximum size of the tumor, MR features, and maximum standardized uptake values (SUV) from PET/CT were obtained. We used Wilcoxon-Rank sum or Fisher's exact tests to compare benign versus malignant nerve sheath tumors. Results: There was no significant difference in the mean age of the patients with benign versus MPNST (P=0.85). Patients with NF1 had higher odds of MPNSTs (OR=26.7, P=2.6 x10-7). There was no difference in the mean size of the benign versus MPNSTs (P=0.44). Homogeneous enhancement of a lesion after intravenous contrast (OR=0.08, P=0.008) and the target sign (OR=0.0, P=0.041), were both associated with decreased odds of MPNST. Bone destruction seen on MRI (P=5.7x10-4) and an enlarged nerve (OR = 3.89, P=0.048) were associated with increased odds of MPNST. MPNSTs had significantly higher mean maximum SUV than benign nerve sheath tumors (P=0.0272). The previously published threshold maximum SUV of 3.5 had 100% sensitivity and 50% specificity to exclude MPNST as 50% (4/8) of the benign nerve sheath tumors had a maximum SUV >3.5. Conclusion: MRI and PET/CT are useful for differentiating benign from MPNST, but neither is specific. A maximum SUV of 3.5 is highly sensitive for identifying MPNST; however, tissue sampling is often necessary to confirm the diagnosis since using this threshold results in a large proportion of false positives. Citation Format: Ronnie Sebro, Paul Niziolek. Utility of MRI and PET/CT to differentiate benign versus malignant peripheral nerve sheath tumors (MPNST) [abstract]. In: Proceedings of the AACR Conference on Advances in Sarcomas: From Basic Science to Clinical Translation; May 16-19, 2017; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(2_Suppl):Abstract nr B17.