Endocrine Abstracts

JOINT3901

Background: Glomus vagale tumors are rare neuroendocrine tumors belonging to the group of head and neck paragangliomas (HNPGLs). The most common symptom is a neck mass, followed by cranial nerve palsies. In very rare instances, vagal paragangliomas (VPGLs) secrete catecholamines. The management of HNPGLs has changed dramatically in recent decades. Surgery was historically the first-line treatment for all HNPGLs and remains the primary approach for functional HNPGLs. While potentially curative, surgery carries a high risk of morbidity, including cranial nerve deficits and vascular injury. In VPGLs, a postoperative vagal deficit is almost inevitable. Fractionated stereotactic radiotherapy (FSRT) has emerged as a viable treatment option for non-secreting HNPGLs, offering excellent long-term tumor control with a low complication rate. However, data on FSRT for functional HNPGLs/VPGLs remain limited.

Case Presentation: A 65-year-old patient presented to the emergency department with syncope. A CT scan revealed a neck mass suspicious for a paraganglioma, prompting further evaluation. There was no evidence of cranial nerve palsy. His past medical history was notable for a 10-year history of hypertension, well controlled with Candesartan and Amlodipine. There were no additional signs or symptoms of catecholamine excess. Biochemical testing revealed significantly elevated plasma-free normetanephrine (6.38 nmol [0.04–1.39 nmol/l]) and methoxytyramine (0.22 nmol/l [<0.06 nmol/l]). MRI demonstrated a VPGL in loco typico, measuring 41 × 20 × 43 mm. Whole-body MRI and DOTATATE-PET/CT showed no evidence of multicentric disease, metastases, or synchronous pheochromocytoma/sympathetic PGL. Genetic testing did not detect pathogenic variants in PGL susceptibility genes. Surgical and radiotherapeutic options were discussed. The patient opted for FSRT. A total dose of 25 Gy in five fractions was administered. Prior to radiotherapy, the patient was started on phenoxybenzamine. During a 11-month follow-up, the patient developed no new symptoms of catecholamine excess. His blood pressure remained well-controlled. On MRI, the VPGL remained stable in size. Plasma metanephrine levels dropped significantly six months post-treatment (normetanephrine: 3.84 nmol/l, methoxytyramine: 0.13 nmol/l) and remained stable at 11 months (normetanephrine: 4.26 nmol/l, methoxytyramine: 0.20 nmol/l), but normalization has not yet been achieved.

Conclusion: Our case demonstrates that FSRT can reduce catecholamine secretion from functional VPGL within a short follow-up period. However, a longer follow-up is necessary to assess the further trajectory of metanephrine levels and to better evaluate the appropriateness of FSRT for managing functional VPGLs. The long-term efficacy and durability of response of FSRT may only become fully apparent over several years.