68Ga-exendin-4 PET/CT detects insulinomas in patients with hypoglycemia in multiple endocrine neoplasia type 1

477 Objectives: Surgical intervention is advised in patients with multiple endocrine neoplasia type-1 (MEN-1) with non-functioning pancreatic neuroendocrine tumors (PanNET) and a size ≥20mm. However, functioning PanNET such as patients with endogenous hyperinsulinemic hypoglycemia (EHH) due to (one or multiple) insulinomas should be treated surgically independent of size. Reliable preoperative localization of insulinomas is critical for surgical strategy. Objectives: To evaluate feasibility and sensitivity of 68Ga-exendin-4 PET/CT in the detection of relevant lesions in MEN-1 patients with EHH in comparison with magnet resonance imaging (MRI). Design: Post-hoc subgroup-analysis of a larger prospective imaging study with 52 EHH patients. Patients: Six of 52 consecutive patients with EHH and genetically proven MEN-1 mutation were included. Interventions: All patients received one 68Ga-exendin-4 PET/CT and one MRI scan within 3-4 days. Thereafter, surgery was performed based on all imaging results. Main Outcome Measures: Lesion-based sensitivity of PET/CT and MRI were calculated. Readers were unaware of other results when reading the scans. Reference standard was surgery with histology and treatment outcome. True positive was defined as PanNET ≥20mm or insulinoma (=relevant lesions). Results: In six patients, 37 PanNET were confirmed by histopathology. Sensitivity (95% confidence interval) for combined PET/CT+MRI, MRI and PET/CT was 92.3% (64%-99.8%), 38.5% (13.9-68.4%) and 84.6% (54.6-98.1%), respectively (P-value=0.014 for the comparison of PET/CT+MRI versus MRI). After surgery, EHH resolved in all patients. Conclusions: 68Ga-exendin-4 PET/CT is feasible in MEN-1 patients with EHH. The combination with MRI is superior to MRI alone in the detection of insulinomas and may guide the surgical strategy.