68 Ga-DOTATATE PET/CT imaging in endogenous hyperinsulinemic hypoglycemia: A tertiary endocrine centre experience.

OBJECTIVE: Literature regarding utility of 68 Ga-DOTATATE PET/CT in insulinoma localization across various subgroups [benign/malignant/multiple endocrine neoplasia-1 (MEN-1) syndrome associated] remains scarce. In this study, the performance of 68 Ga-DOTATATE PET/CT was compared with contrast-enhanced computed tomography (CECT) and 68 Ga-NODAGA-Exendin-4 PET/CT (whenever available) in an endogenous hyperinsulinemic hypoglycemia (EHH) cohort. DESIGN: Retrospective audit. PATIENTS: EHH patients [N = 36, lesions (n) = 49, final diagnosis: benign sporadic insulinoma (BSI) (N = 20), malignant insulinoma (N = 4, n = 14), MEN-1 syndrome associated insulinoma (N = 9, n = 15), Munchausen syndrome (N = 2) and drug-induced hypoglycemia (N = 1)] having both preoperative imaging modalities (CECT and 68 Ga-DOTATATE PET/CT). MEASUREMENTS: Per-lesion sensitivity (Sn) and positive predictive value (PPV) for histopathological diagnosis of insulinoma. RESULTS: Sn and PPV of 68 Ga-DOTATATE PET/CT were 67.3% and 89.2%; 55% and 100%; 85.7% and 100%; and 66.7% and 77% for overall EHH, BSI, malignant, and MEN-1 syndrome associated insulinoma cohorts respectively. Despite having comparatively lower sensitivity in BSI cohort, 68 Ga-DOTATATE PET/CT localized a pancreatic tail lesion missed by other modalities. 68 Ga-DOTATATE PET/CT had comparatively higher sensitivity in malignant insulinoma than BSI cohort. 68 Ga-DOTATATE PET/CT also paved the way for successful response to 177 Lu-based peptide receptor radionuclide therapy (PRRT). In MEN-1 cases, lower PPV as compared with BSI was due to uptake in non-insulinoma pancreatic neuroendocrine tumours (Pan-NET). CONCLUSIONS: 68 Ga-DOTATATE PET/CT has supplemental role in selected cases of BSI with negative and/or discordant results with CECT and 68 Ga-NODAGA-Exendin-4 PET/CT. In malignant insulinoma, 68 Ga-DOTATATE-PET/CT has an additional theranostic potential. Interference due to uptake in non-insulinoma Pan-NET in MEN-1 syndrome may hinder insulinoma localization with 68 Ga-DOTATATE-PET/CT.