68Ga-exendin-4

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.

Objective: To explore the accuracy in localizing occult insulinomas with Glucagon-like peptide-1 receptor(GLP-1R) PET-CT with (68)Ga-exendin-4. Methods: In this prospective cohort study, patients with biochemically proven endogenous hyperinsulinemic hypoglycemia and negative contrast-enhanced CT with pancreatic perfusion scans were enrolled consecutively at Department of Nuclear Medicine, Peking Union Medical College Hospital from February 2014 to June 2018.There were 37 males and 32 females, with age of (43.2±17.9)years. (68)Ga-exendin-4 PET-CT, MRI and endoscopic ultrasound(EUS) were done before elective surgery. Sensitivity, specificity, accuracy, positive predictive value(PPV) and negative predictive value(NPV) of the above imaging modalities were calculated. Results: A total of 69 patients were recruited. Thirty-two patients were diagnosed with insulinomas at histology. Four patients with positive (68)Ga-exendin-4 PET-CT findings did not undergo surgery so far. Twenty-eight patients were proven to be noninsulinoma induced hyperinsulinemic hypoglycemia. Five patients were unknown of etiology of hypoglycemia. The sensitivity, specificity, accuracy, PPV and NPV of (68)Ga-exendin-4 in localizing occult insulinomas were 96.9%(31/32), 100%(30/30), 98.3%(59/60), 100%(29/29), 96.8%(30/31), respectively.The sensitivity, specificity, accuracy, PPV and NPV of MRI were 74.1%(20/27), 9/11, 76.3%(29/38), 90.9%(20/22), 9/16, respectively. The sensitivity, specificity, accuracy, PPV and NPV of EUS were 75.0% (15/20), 2/2, 77.3%(17/22), 15/15, and 2/7. Conclusion: (68)Ga-exendin-4 PET-CT has a high sensitivity, specificity and accuracy for detection of occult insulinoma, which shows superiority to MRI and EUS.