Exendin PET/CT for Imaging of Paragangliomas

Rationale: Functional imaging of paragangliomas (PGLs) is not unequivocal. Existing functional imaging modalities show good but variable results in PGLs, warranting the search for additional molecular imaging targets. Investigators aim to evaluate the glucagon-like peptide 1 receptor (GLP-1R) as a novel target for molecular imaging of PGLs. For this purpose investigators will use the tracer 68Ga-NODAGA-exendin 4 for positron emission tomography/computed tomography (PET/CT) imaging. Objective: The primary objective is to examine the feasibility of 68Ga-exendin-4 PET/CT for localization and functional characterization of PGLs. Study design: In this prospective pilot imaging study 68Ga-exendin-4 PET/CT will be performed in 10 patients with confirmed PGL who have undergone CT, somatostatin receptor (SSTR) PET/CT and 18F-FDG PET/CT (as standard diagnostic procedures) and are scheduled for surgery. 100 ± 10 MBq 68Ga-NODAGA-exendin-4 will be administered to 10 patients in total. In the first 5 patients PET/CT imaging will be performed 1, 2 and 4 hours after injection to determine the optimal imaging timepoint for the remainder of the patients, which will be applied in the remaining patients. The images will be reconstructed and evaluated by a nuclear medicine physician who is blinded to the results of the CT, SSTR PET/CT and 18F-FDG PET/CT to assess tumor detection. Additionally, quantitative analysis of 68Ga-exendin-4, SSTR PET and 18F-FDG PET/CT images will be performed. After the patients have undergone surgery, immunohistochemical analysis of surgical specimens will be performed to assess GLP-1R expression, which will be compared with in vivo tracer uptake.