(ChemotherapyAdvisor) – In vivo imaging is a non-invasive diagnostic approach to successfully localize small insulinomas, according to a multinational group of researchers. This conclusion is based on a paper entitled “Glucagon-like peptide 1 receptor (GLP-1R) imaging for the preoperative localization of benign insulinomas in 30 patients,” which was presented on May 7 at the annual meeting of the European Society of Endocrinology in Florence, Italy.

The investigators premised this study on several lines of evidence. First, they cite that although biochemical diagnosis of endogenous hyperinsulinemic hypoglycemia is straightforward, surgical removal of an insulinoma is hampered by difficulties to localize it using conventional radiological procedures (endosonography, MRI, CT-imaging techniques). Second, the investigators cite that in vitro data suggest that human insulinoma cells exhibit a high density of GLP-1R.

The investigators hypothesized that diagnostic administration of 111In-exendin-4, a 111In-labeled GLP-1R agonist that binds with high affinity to GLP-1R, may be helpful in localizing benign insulinomas. The main aim of this study was to localize benign insulinomas by administering 111In-exendin-4 to patients that meet the inclusion criteria: endogenous hyperinsulinemic hypoglycemia and 0 or 1 suspicious lesion upon conventional imaging.

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111In-exendin-4 was intravenously administered (≈90 MBq; 30μg peptide) to 30 patients. After administration, whole body planar images and SPECT/CT images of the abdomen were performed at various time points post-injection, which was followed by diagnostic histology to confirm the presence of insulinomas.

Conventional imaging identified 17 insulinoma-positive patients. “In comparison, 111In-exendin-4 SPECT/CT detected 23 true positive benign insulinomas and 5 additional positive lesions. The positive predictive value was 85% and the negative predictive value was 100%.”

The investigators concluded: “These data suggest that in vivo GLP-1R imaging defines a new non-invasive diagnostic approach to successfully localize small insulinomas.”