We report a retrospective, single centre observational study to determine the characteristics and outcomes of pancreatic insulinoma. Interrogation of the Oxford NET database, a departmental database of new NET MDT referrals since 2011 (n = 1059), revealed 23/1059 (2.1%) patients with insulinoma diagnosed and treated between 2011 and 2018. Patient records were reviewed and data was captured on demographics, presentation, investigations, treatments and outcomes: 15/23 (65.2%) patients were female; mean (and standard deviation, S.D.) age at diagnosis was 50.9 (17.4) years. Insulinoma was sporadic in 18/23 (78.3%) patients, associated with multiple endocrine neoplasia type 1 (MEN1) in 4/23 (17.4%) patients, and with neurofibromatosis type 1 in a single (1/23, 4.4%) patient. Symptomatic hypoglycaemia presented in 22/23 (95.7%) patients, while 1/23 (4.4%) asymptomatic patient presented following radiological screening for MEN1-associated tumours. One of 22 (4.6%) patients presenting with hypoglycaemia had known metastatic non-functioning pancreatic NET that transformed to a functional insulinoma. Five of 22 (22.7%) patients presenting with symptomatic hypoglycaemia had biochemical confirmation during unprovoked hypoglycaemia, while 17/22 (77.3%) patients required prolonged fasting to induce hypoglycaemia. Prolonged fasting provoked hypoglycaemia at an average (S.D.) of 24.9 (19.4) hours. Complete data on radiological investigations were available for 22/23 (95.7%) patients: 20/22 (90.9%) patients underwent MRI, identifying a pancreatic lesion(s) in all cases. Confirmatory testing was with calcium stimulation testing in 18/22 (81.8%) patients and endoscopic ultrasound (EUS) in 9/22 (40.9%) patients, with biopsy obtained in 2/9 (22.2%) patients. Three of 23 (13%) patients had metastatic disease at diagnosis and were unsuitable for curative resection; 2/23 (8.7%) patients were medically managed, while the remaining 18/23 (78.3%) underwent surgical resection with resolution of hypoglycaemia. After a mean (S.D.) follow-up of 5.0 (2.5) years there has been a single death due to metastatic insulinoma. None of the surgically resected insulinomas have recurred. Based on these data we conclude that insulinoma remains an uncommonly encountered condition even in a high-volume NET centre. Prognosis following curative resection is excellent, although the work-up remains complex and a significant minority of patients present with metastatic disease.
02 Dec 2019
UK and Ireland Neuroendocrine Tumour Society