Limited Value of 18F-F-DOPA PET to Localize Pancreatic Insulin-Secreting Tumors in Adults with Hyperinsulinemic Hypoglycemia

Context: Fluorine-18-l-dihydroxyphenylalanine positron emission tomography (18F-FDOPA PET) imaging is increasingly used in the workup of neuroendocrine tumors. It has been shown to be an accurate tool in the diagnosis of congenital hyperinsulinism, but limited information is available on its value in adult disease. Objective, Patients, and Design: The objective of this study was to review our experience with 18F-FDOPA PET imaging in six consecutive patients with hyperinsulinemic hypoglycemia (HH) (four solitary insulinomas, one diffuse β-cell hyperplasia, one malignant insulinoma). 18F-FDOPA uptake was also evaluated in 37 patients (43 procedures) without HH or other pancreatic neuroendocrine tumors, which acted as a control group. Results: Using visual analysis, 18F-FDOPA-PET proved positive in only one case (a multiple endocrine neoplasia type 1 related insulinoma). In diffuse β-cell hyperplasia, the pancreatic uptake was similar to controls. In the patient with liver metastases, the extent of disease was underestimated. The pancreatic uptake was not statistically different between controls and hyperinsulinemic patients. The main limitation for identifying insulinomas or β-cell hyperplasia in adults appears to be to the 18F-FDOPA uptake and retention in the whole pancreas. This drawback is potentially circumvented in focal hyperplasia in newborns due to a lower aromatic amino acid decarboxylase expression in the extralesional pancreatic parenchyma. Conclusions: 18F-FDOPA PET is of limited value in localizing pancreatic insulin secreting tumors in adult HH. Our results contrast with the referential study and require further analysis. The limited value of 18F-FDOPA PET for tumor localization in adults with hyperinsulinemic hypoglycemia is mainly due to high tracer uptake and retention in the whole pancreas.