Glucagon-like peptide-1 receptor (GLP-1R)-targeted PET imaging with 68Ga-labeled compounds is able to provide superior sensitivity and specificity to detect insulinoma, like the widely studied [68Ga]Ga-NOTA-exendin-4. This pilot study was prospectively designed to evaluate the early dynamic distribution of [68Ga]Ga-HBED-CC-exendin-4, a novel radiopharmaceutical targeting GLP-1R, which was compared with [68Ga]Ga-NOTA-exendin-4 in the same group of insulinoma patients.

Insulinoma is the most common cause of endogenous hyperinsulinemic hypoglycemia in adult patients without diabetes. The only curative treatment of an insulinoma is its surgical removal. Therefore, exact preoperative localization of the insulinoma is critical to planning the surgical intervention. MR imaging, CT, or endoscopic ultrasound is normally used to localize insulinomas. However, the small size of the tumors (often,1 cm) limits the sensitivity of these methods. In recent years, a new receptor-targeted imaging technique, glucagon-like peptide-1 receptor (GLP-1R) imaging, for detecting insulinoma has been established. GLP-1R is expressed on benign insulinoma cell surfaces with very high incidence (>90%) and density (8,133 dpm/mg of tissue). No other peptide receptor has been found to exhibit such high expression levels in insulinoma. [68Ga]Ga-HBED-CC-exendin-4, a novel radiopharmaceutical targeting GLP-1R, with the urea fragment of a conjugate that employs the HBED-CC chelator for labeling with 68Ga in order to In order to reduce the accumulation of radioactivity in the kidneys. This pilot study was prospectively designed to evaluate the early dynamic distribution of [68Ga]Ga-HBED-CC-exendin-4 compared with [68Ga]Ga-NOTA-exendin-4 in the same group of Insulinoma patients.

Inclusion Criteria:

• confirmed treated or untreated insulinoma patients;
• [68Ga]Ga-HBED-CC-exendin-4 and [68Ga]Ga-NOTA-exendin-4 PET/CT within two consecutive days;
• signed written consent.

Exclusion Criteria:

• pregnancy;
• breastfeeding;
• known allergy against exendin-4;
• any medical condition that in the opinion of the investigator may significantly interfere with study compliance