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

Abstract

Our objective was to assess the value of ⁶⁸Ga-DOTATOC and carbidopa-assisted ¹⁸F-fluorodihydroxyphenylalanine (¹⁸F-DOPA) in 21 hypoglycemic patients. Methods: All patients who underwent ⁶⁸Ga-DOTATOC or carbidopa-assisted ¹⁸F-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 ⁶⁸Ga-DOTATOC and ¹⁸F-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. ¹⁸F-DOPA and ⁶⁸Ga-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 ¹⁸F-DOPA PET/CT and 3 by ⁶⁸Ga-DOTATOC PET/CT only. ¹⁸F-DOPA and ⁶⁸Ga-DOTATOC PET/CT were falsely positive in 1 nonfunctioning pancreatic neuroendocrine tumor. Conclusion: When ⁶⁸Ga-exendin-4 is not available, ⁶⁸Ga-somatostatin receptor PET/CT should be the first choice for insulinoma functional imaging.