E-Poster Presentation ESA-SRB-ANZBMS 2021

Background:

Insulinoma is exceptionally rare in a patient with pre-existing diabetes but important not to miss as a cause of debilitating hypoglycaemia. Managing recurrent hypoglycaemia in metastatic unresectable insulinoma is extremely challenging given lack of definitive surgical cure, poor prognosis and limitations of available options e.g. paucity of data, modest efficacy and patient intolerance.

Case Presentation:
We describe a 90-year-old man with insulin-dependent type 2 diabetes mellitus (T2DM) who, despite insulin cessation, presented with recurrent hypoglycaemia (2.5 mmol/L) associated with confirmed inappropriate endogenous hyperinsulinaemia (24 µIU/mL). Sulfonylurea use and insulin antibodies were excluded. CT abdomen detected three large arterially-enhancing liver lesions. DOTATATE PET/CT scans showed increased activity in the pancreatic tail and extensive liver metastases. Liver biopsy confirmed well-differentiated metastatic neuroendocrine tumour. He was unsuitable for surgical resection and failed Octreotide therapy. Four cycles of Lutate resulted in hypoglycaemia resolution and he is currently well 5-years after Lutate with sustained clinical, biochemical and radiological response.

Discussion:

Literature review yielded 13 cases of metastatic insulinoma in pre-existing diabetes. Majority had T2DM (mean age 59 years at diagnosis). The most common primary site was pancreatic tail with liver being the most common site of metastases. Lutate has not otherwise been reported in a diabetic patient with metastatic insulinoma. Treatment outcomes were mixed. Literature review revealed 33 cases of Lutate in metastatic insulinoma. Vast majority had positive outcome with interpretation limited by publication bias and short follow-up.

Conclusions:

This case is unique due to the paradoxical entity of insulinoma in insulin-dependent diabetes and positive sustained outcome after Lutate despite poor expected prognosis. Lutate is a potential effective and well-tolerated treatment option in unresectable metastatic insulinoma with benefits including hypoglycaemia resolution and reduction in metastatic burden. However given scarce data, further controlled studies exploring Lutate efficacy in these patients is warranted.