Localization of Hidden Insulinomas with 68Ga-DOTA-Exendin-4 PET/CT: A Pilot Study

In-111-DOTA-exendin-4 SPECT/CT has been shown to be highly efficient in the detection of insulinomas. We aimed at determining whether novel PET/CT imaging with [NIe(14),Lys(40)(Ahx-DOTA-Ga-68) NH2]exendin-4 (Ga-68-DOTA-exendin-4) is feasible and sensitive in detecting benign insulinomas. Methods: Ga-68-DOTA-exendin-4 PET/CT and In-111-DOTA-exendin-4 SPECT/CT were performed in a randomized cross-over order on 5 patients with endogenous hyperinsulinemic hypoglycemia. The gold standard for comparison was the histologic diagnosis after surgery. Results: In 4 patients histologic diagnosis confirmed a benign insulinoma, whereas one patient refused surgery despite a positive Ga-68-DOTA-exendin-4 PET/CT scan. In 4 of 5 patients, previously performed conventional imaging (CT or MR imaging) was not able to localize the insulinoma. Ga-68-DOTA-exendin-4 PET/CT correctly identified the insulinoma in 4 of 4 patients, whereas In-111-DOTA-exendin-4 SPECT/CT correctly identified the insulinoma in only 2 of 4 patients. Conclusion: These preliminary data suggest that the use of Ga-68-DOTA-exendin-4 PET/CT in detecting hidden insulinomas is feasible.