FDG PET-CT imaging in head and neck paragangliomas: a center experience.

Head and neck paragangliomas (HNPGLs) are rare tumors with ~30% genetic mutations, mainly in succinate dehydrogenase (SDHx) genes. The utility of FDG PET-CT in HNPGLs is questioned by recent developments in novel radiotracers. We therefore performed a retrospective study in a single tertiary referral center to address the utility of FDG PET/CT in HNPGLs.Clinical data on genetic testing and follow-up was collected for patients who had FDG PET-CT scans from 2004-2016. Receiver operator characteristic (ROC) analysis was used to compare standardized uptake values (SUVs), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) between lesions in patients who had a clinically-related event: event (+) and those that did not: event (-). Similarly, we compared PET parameters between SDHx+ patients and a control group with low probability of mutation.Of 153 HNPGLs patients, 73 (29 SDHx+) with 93 FDG-positive lesions were identified: 53.8% of lesions were assessed in a pre-therapeutic setting. In comparison to a reference extracted from clinic-radiological database, FDG PET-CT showed good performance to detect HNPGLs (96.6% Accuracy). In this study population, 16 disease progression, 1 recurrence and 1 death were recorded and event (+) patients had lesions with higher SUVmax (p=0.03 and p=0.02, respectively). Conversely, there were no differences in PET parameters between lesions in SDHx+ patients and controls with low probability of SDHx+ mutations.FDG PET-CT has clinical utility in HNPGLs, mostly before local treatment. There were no significant differences in PET parameters between SDHx patients and a sporadic HNPGL population. However, regardless of SDHx mutation status, a high SUVmax was associated with more clinical events and prompts to a closer follow up.

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Authors: Sarah Boughdad, Ann O'Connor, Gary J Cook, Lucy Pike, Steve Connor, Rupert Obholzer, Victoria Warbey