Value of Ga-68-DOTATOC and Carbidopa-Assisted F-18-DOPA PET/CT for Insulinoma Localization

Our objective was to assess the value of Ga-68-DOTATOC and carbidopa-assisted F-18-fluorodihydroxyphenylalanine (F-18-DOPA) in 21 hypoglycemic patients. Methods: All patients who underwent Ga-68-DOTATOC or carbidopa-assisted F-18-DOPA PET/CT for suspicion of insulinoma from January 2019 to January 2021 were retrospectively analyzed. A final diagnosis of insulinoma was determined by pathologic reports or consensus. Results: During the study period, 21 patients underwent both Ga-68-DOTATOC and F-18-DOPA PET/CT. A final diagnosis of insulin-secreting tumor was reached in 12 cases, including 11 insulinomas and 1 small mixed neuroendocrine/nonneuroendocrine neoplasm. F-18-DOPA and Ga-68-DOTATOC PET/CT were positive in 5 (45%) and 7 (64%) of 11 cases, respectively, with 4 concordant positive findings. Moreover, 1 insulinoma was visualized exclusively by F-18-DOPA PET/CT and 3 by Ga-68-DOTATOC PET/CT only. F-18-DOPA and Ga-68-DOTATOC PET/CT were falsely positive in 1 nonfunctioning pancreatic neuroendocrine tumor. Conclusion: When Ga-68-exendin-4 is not available, Ga-68-somatostatin receptor PET/CT should be the first choice for insulinoma functional imaging.