Purpose: We aim at prospectively comparing the detection rate of GLP1-R PET/CT vs GLP1-R SPECT/CT vs standardized contrast enhanced 3T-MRI in patients with suspected insulinoma.
Methods: 40 patients with neuroglycopenic symptoms due to endogenous hyperinsulinemic hypoglycemia were enrolled.
3T-MRI was performed. Afterwards patients received SPECT/CT after injection of 111In-DOTA-exendin-4 and PET/CT after injection of 68Ga-DOTA-exendin-4 in a randomized order. Three blinded nuclear medicine physicians and three blinded radiologists reviewed the scans.
Standard of comparison was the histological diagnosis after surgery.
Results: Previously performed cross-sectional imaging was negative or inconclusive in 27/40 patients. So far 29 patients have been operated. The histological diagnosis of a benign insulinoma was confirmed in 25 patients, one patient had a nesidioblastosis. In one patient no lesion could be found intraoperatively. In two patient symptoms of endogenous hypoglycemia ceased postoperative but histological diagnosis did not confirm a benign insulinoma or nesidioblastosis. These two patients were excluded from evaluation as the final diagnosis remained unclear. Two patients refused surgery. Three patients are awaiting surgery. In five patients all performed imaging modalities did not find any suspicious lesion and were thus not operated up to date. One patient showed signs of malignancy in MRI, thus did not meet the inclusion criteria and was excluded. In this interim analysis of 27 operated patients PET/CT showed an overall pooled sensitivity of 92%, SPECT/CT at 72 h a sensitivity of 71% and 3T-MRI a sensitivity of 76%.
Conclusion: 1) These preliminary data suggest that PET/CT performs better as standardized MRI imaging and SPECT/CT at lower irradiation dose and much shorter investigation time than the latter.
2) GLP-1R PET/CT will be a useful diagnostic tool in patients where CT/MRI fails to localize the insulinoma.
20 - 23 May 2017
European Society of Endocrinology