Glucagon-like peptide-1 receptor PET/CT in gastrinomas: a case series demonstrating the precise characterization to guide surgical and medical treatment.

Gastrinoma is a rare type of neuroendocrine tumor with ectopic secretion of gastrin causing Zollinger-Ellison syndrome (ZES). Accurate localization of gastrinomas and their metastases is important for developing precise treatment strategies. We reported three cases of metastatic gastrinomas evaluated with 68Ga-exendin-4 and 68Ga-DOTANOC PET/CT. Despite most gastrinomas highly expressing somatostatin receptor (SSTR), these patients showed no or heterogeneous uptake on 68Ga-DOTANOC PET/CT, whereas 68Ga-exendin-4 PET/CT sensitively detected the primary tumor, lymph node metastasis, liver metastasis, and bone metastasis, facilitating accurate tumor assessment and supporting clinical decision-making. The findings were correlated with enhanced CT and MRI and confirmed the location of the hormone-related tumors. This highlights the potential utility of 68Ga-exendin-4 PET/CT as a promising imaging modality for evaluating gastrinomas with no or heterogeneous SSTR expression and guiding precise treatment strategies.