PSUN372 Insulinoma in an Elderly Woman with History of Distal Pancreatectomy: Treatment Challenges
Authors: Friedman Sally B , Anderson Karolina , Hendrickson Chase , Bao Shichun 
Published: November 2022

Abstract

Introduction
Insulinomas are rare pancreatic tumors with an incidence of 1-4/million/year. A majority of patients undergo definitive surgical management (tumor enucleation 43%, distal pancreatectomy 45%, pancreaticoduodenectomy 12%)1. However, surgery may not be prudent for all patients. We present a case of an elderly woman with prior distal pancreatectomy who developed an insulinoma in the pancreatic remnant and considerations for definitive management given risk of progression to pancreoprivic diabetes with surgical intervention.

Clinical Case
The inpatient endocrinology service was consulted to evaluate a 72-year-old woman presenting with recurrent, severe hypoglycemia. History was notable for necrotizing hemorrhagic pancreatitis requiring resection of the pancreatic body and tail and T2DM treated with metformin monotherapy. Metformin was self-discontinued 6 months earlier due to hypoglycemia. Hypoglycemia progressed to daily occurrence with some severely low glucose readings of 30-50 mg/dL and associated confusion, tremulousness, and diaphoresis. She felt compelled to eat hourly to prevent hypoglycemia, resulting in weight gain. A 72-hour fasting study was initiated and resulted in symptomatic hypoglycemia with biochemical profile suggestive of insulinoma: inappropriately high insulin 51.5 mcunit/mL (normal 0.0-16.0 mcunit/mL), proinsulin 124.8 pmol/L (normal ≤ 8.0 pmol/L), and c-peptide 12.5 ng/mL (normal 0.7-5.2 ng/mL) despite severely low blood glucose of 24 mg/dL. HbA1c was 5.9%. Sulfonylurea screen and insulin antibody testing were negative. MRI/MRCP of the abdomen demonstrated a 1.6 cm hypervascular lesion in the pancreatic uncinate process consistent with a neuroendocrine tumor and prior distal pancreatectomy. Diazoxide was initiated at 3 mg/kg/day for medical management of hypoglycemia. Endocrine surgery recommended tumor enucleation versus completion pancreatectomy pending intraoperative anatomical assessment. The patient was counseled regarding risk of progression to insulin-dependent diabetes with enucleation and certainty of pancreoprivic diabetes with completion pancreatectomy. After thorough risk-benefit discussion, these outcomes were deemed unacceptable by the patient who affirmed that her priority was to avoid insulin-dependence. She was thus discharged on diazoxide 75 mg BID. Libre 2 CGM was initiated during the hospitalization with plan for continued intensive monitoring as an outpatient.

Conclusion
The development of an insulinoma in remnant pancreatic parenchyma following partial pancreatectomy represents a clinical quandary in which surgery can be curative but predisposes to a labile form of insulin-dependent diabetes. Determination of an optimal management strategy must include discussion of all possible outcomes and place appropriate value on patient goals. Medical management of insulinoma-related hypoglycemia may be favorable in some settings, particularly in the era of CGM systems with hypoglycemia alerts.

References
1. Peltola E., Hannula P., Huhtala H., et al. Characteristics and Outcomes of 79 Patients with an Insulinoma: A Nationwide Retrospective Study in Finland. Int J Endocrinol. 2018;2018: 2059481. Published 2018 Oct 23. doi: 10.1155/2018/2059481
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