Glucagon-like peptide-1 receptor imaging with [Lys40(Ahx-HYNIC- 99mTc/EDDA)NH2]-exendin-4 for the detection of insulinoma

Abstract

Purpose: The objective of this article is to present a new method for the diagnosis of insulinoma with the use of [Lys(40)(Ahx-HYNIC-(99m)Tc/EDDA)NH2]-exendin-4.

Methods: Studies were performed in 11 patients with negative results of all available non-isotopic diagnostic methods (8 with symptoms of insulinoma, 2 with malignant insulinoma and 1 with nesidioblastosis). In all patients glucagon-like peptide-1 (GLP-1) receptor imaging (whole-body and single photon emission computed tomography/CT examinations) after the injection of 740 MBq of the tracer was performed.

Results: Both sensitivity and specificity of GLP-1 receptor imaging were assessed to be 100 % in patients with benign insulinoma. In all eight cases with suspicion of insulinoma a focal uptake in the pancreas was found. In six patients surgical excision of the tumour was performed (type G1 tumours were confirmed histopathologically). In one patient surgical treatment is planned. One patient was disqualified from surgery. In one case with malignant insulinoma pathological accumulation of the tracer was found only in the region of local recurrence. The GLP-1 study was negative in the other malignant insulinoma patient. In one case with suspicion of nesidioblastosis, a focal accumulation of the tracer was observed and histopathology revealed coexistence of insulinoma and nesidioblastosis.

Conclusion: [Lys(40)(Ahx-HYNIC-(99m)Tc/EDDA)NH2]-exendin-4 seems to be a promising diagnostic tool in the localization of small insulinoma tumours, but requires verification in a larger series of patients.

Fig. 1

Patient J.A. (57 years old) with clinically overt hypoglycaemia. The examination with the GLP-1 analogue labelled with ^99mTc revealed focal accumulation of the tracer. The well-differentiated neuroendocrine tumour type G1 was found in the histopathological study after surgical excision of the part of the pancreas head selected during GLP-1 receptor imaging study. a Fusion of GLP-1 receptor imaging and CT sagittal slice. b Fusion of GLP-1 receptor imaging and CT axial slice. c Fusion of GLP-1 receptor imaging and CT coronal slice

Fig. 2

Patient A.U. (31 years old) with nesidioblastosis. The examination with the GLP-1 analogue labelled with ^99mTc revealed focal accumulation of the tracer in the pancreatic head. Insulinoma with coexisting nesidioblastosis was confirmed in the histopathological examination after surgery. a CT study. b Fusion of GLP-1 receptor imaging and CT. c GLP-1 receptor imaging

Fig. 3

Tumour to non-tumour ratio (T/nT) and kidney to non-tumour ratio (K/nT) over time (means ± SD). The T/nT remained relatively stable over time, while the K/nT decreased visibly (~ 40 % from the time of injection to 6 h after injection)