Endocrine Abstracts

Paragangliomas are rare neuroendocrine tumours that often pose significant diagnostic and management challenges. A 69-year-old male was referred to our hospital for investigation of an incidentally discovered retroperitoneal mass on a staging computed tomography (CT) scan after a recently diagnosed low-grade bladder cancer (biopsy proven). His other past medical history included severe ischaemic heart disease, hypertension, atrial fibrillation, type 2 diabetes and psoriasis. Symptomatically, the patient only reported occasional palpitations with a normal blood pressure on antihypertensive therapy (losartan, amlodipine). Initial biochemical testing revealed elevated plasma 3-methoxytyramine (7995 [0-180]) with normal metanephrine (344 [0-150]) and normetanephrine (878 [0-1180]) levels. Positive emission topography (PET)/CT scans with 18F-fluorodeoxyglucose and gallium-68 dotatoc supported the diagnosis of a localised retroperitoneal paraganglioma (5.6x5.6 cm). Germline mutational screening revealed a mutation in the succinate dehydrogenase B (SDHB) gene. Following anaesthetic assessment, surgery was deemed to carry excessive risk, and the patient was referred for precision radiation therapy (RT). He completed a dose attenuated course of RT of 30Gy delivered in 5 alternate-day treatments due to proximity of the small bowel. He did not have any CTCAE V 5.0 Grade 3 or above toxicities and demonstrated a radiological RECIST criteria partial response at his 3-month post treatment assessment scan. In the 33 months we have been following him up since RT, there has been both a biochemical (3-methoxytyramine 7995 pmol/l to 695 pmol/l) and radiological response (progressive reduction in tumour size to 50% of original). He has not had any evidence of new or metastatic paragangliomas on biochemical and imaging surveillance. This case highlights the importance of personalised multidisciplinary management strategies in patients with paragangliomas. It demonstrates that precision RT is a promising palliative option for localised disease in patients who are unable to undergo potentially curative surgery.