GLP-1 and exendin-4 for imaging endocrine pancreas. A review. Labelled glucagon-like peptide-1 analogues: past, present and future.

Glucagon-like peptide 1 (GLP-1) receptors expression has been found on many types of cancer cells. In case of benign insulinoma the density of those receptors is even higher than the density of somatostatin receptors. This article presents the results of clinical trials proving the utility of GLP-1 receptors imaging. Scintigraphy or positron emission tomography with the use of GLP-1 analogues labelled with appropriate radioisotopes (111In, 99mTc, 68Ga, 18F or 64Cu) seem to be superior compared with other available techniques in diagnosis of hardly detectable benign insulinoma. While surgery is the only effective therapy for insulinoma patients, therefore proper preoperative localization of the tumor allows sparing operation. Glucagon-like peptide 1 receptors might become also a target for imaging of other tumors such as gastrinoma, pheochromocytoma and medullary thyroid cancer (MTC), which also were shown to overexpress this type of receptors. However, studies with larger groups of patients are required to prove the clinical usefulness of this indication. Moreover GLP-1 receptor imaging seems to be a potential tool to evaluate pancreatic beta cell mass (BCM). It may be useful in the early diagnosis of beta cell loss in preclinical phases of diabetes. The panceratic beta cells imaging may influence the prophylaxis of diabetes and management of diabetic patients. Presented results of clinical trials prove that glucagon-like peptide 1 receptor imaging might become helpful diagnostic strategy particularly in case of patients with benign insulinoma tumors, but also patients with gastrinoma, pheochromocytoma, medullary thyroid cancer and diabetes.