Endogenous hyperinsulinism caused by an insulinoma is a rare condition, potentially causing severe hypoglycaemia. The definite therapy for insulinoma is a pancreas-sparing surgery. That is why accurate preoperative localization of the tumour is important. However, most insulinomas are solitary, benign and rather small in size, which often makes their localization difficult. In about 10% of insulinomas, conventional imaging (CT, EUS, MRI, somatostatin receptor scintigraphy) is negative. Glucagon-like peptide-1 receptors (GLP-1R) are expressed in high percentage and density in virtually all insulinomas. The aim of this study was to evaluate GLP-1R imaging with the use of [Lys40(Ahx-HYNIC-99mTc/EDDA)NH2]-exendin-4 in localization of insulinoma, when conventional imaging was negative or inconclusive.
Whole-body GLP-1R SPECT/CT was performed four hours after administration of [Lys40(Ahx-HYNIC-99mTc/EDDA)NH2]-exendin-4 in patients with suspected insulinoma and negative or inconclusive conventional imaging (CT/EUS/MRI/SRS). The results of the GLP-1R scintigraphy were evaluated by an experienced nuclear medicine physician. Following surgical excision of the lesion, the diagnostic performance of the GLP-1R scintigraphy was analysed using histopathological evaluation and patient’s symptoms resolution as the gold standard.
Seven female patients with biochemically confirmed endogenous hyperinsulinism during fasting test were enrolled in our study. In all patients, focal uptake of the radiopharmaceutical in the pancreas was found and surgery was performed. No metastases were found. In all cases, insulin-producing neuroendocrine tumors were confirmed by histopathological analysis and patient’s symptoms resolved after surgery. The sensitivity and specificity of GLP-1R scintigraphy were 100%.
GLP-1R imaging with the use of [Lys40(Ahx-HYNIC-99mTc/EDDA)NH2]-exendin-4 is a highly efficient diagnostic modality for localization of insulinoma.