Detection of Metastatic Insulinoma by Positron Emission Tomography with [(68)Ga]Exendin-4 - : a case report

• Context: Insulinomas are the most common cause of endogenous hyperinsulinaemic hypoglycaemia in non-diabetic adult patients. They are usually benign and curative surgery is the "gold standard" treatment if they can be localized. Malignant insulinomas are seen in less than 10% and their prognosis is poor. The Glucagon Like Peptide-1 receptor (GLP-1R) is markedly upregulated in insulinomas - especially benign lesions which are difficult to localize with current imaging techniques.Objective:To assess the possibility of the detection of primary and metastatic insulinoma by PET using [(68)Ga]Ga-DO3A-VS-Cys(40)-Exendin-4 ([(68)Ga]Exendin-4) in a patient with severe hypoglycemia.Design:Dynamic and static PET/CT examination of a patient using [68Ga]Exendin-4.Setting:Uppsala University Hospital, Uppsala, Sweden.Patients:A patient presented with hypoglycemia requiring continuous intravenous glucose infusions. A pancreatic insulinoma was suspected and an exploratory laparotomy was urgently performed. At surgery, a tumor in the pancreatic tail with an adjacent metastasis was found and a distal pancreatic resection (plus splenectomy) and removal of lymph node was performed. Histopathology showed a WHO grade II insulinoma. Postoperatively hypoglycemia persisted but a PET/CT examination using the neuroendocrine marker [(11)C]-5-hydroxy-L-tryptophan was negative.Interventions:The patient was administered with [(68)Ga]Exendin-4 and examined by dynamic PET over the liver and pancreas.Main Outcome Measures:N/AResults:The stable GLP-1 analogue Exendin-4 was labeled with (68)Ga for PET imaging of GLP-1R expressing tumors. The patient was examined by [(68)Ga]Exendin-4-PET/CT which confirmed several small GLP-1R positive lesions in the liver and a lymph node that could not be conclusively identified by other imaging techniques. The results obtained from the [(68)Ga]Exendin-4-PET/CT examination provided the basis for continued systemic treatment.Conclusion:The results of the [(68)Ga]Exendin-4-PET/CT examination governed the treatment strategy of this particular patient and demonstrated the potential of this technique for future management of patients with this rare, but potentially fatal disease.

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MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine (hsv//eng)

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