title: Glucagon-like peptide-1 receptor imaging for localization of insulinomas.
abstract: BACKGROUND
  The surgical removal of insulinomas is hampered by difficulties to localize it using conventional radiological procedures. Recently these tumors were shown to exhibit a very high density of glucagon-like peptide-1 receptors (GLP-1R) in vitro that may be used as specific targets for in vivo receptor radiolabeling.
  
  
  OBJECTIVE
  The objective of the study was to test the 111In-labeled GLP-1R agonist 111In-DOTA-exendin-4 in localizing insulinomas using single photon emission computed tomography in combination with computed tomography images.
  
  
  METHODS
  This was a prospective open-label investigation.
  
  
  METHODS
  The study was conducted at three tertiary referral centers in Switzerland.
  
  
  METHODS
  Patients included six consecutive patients with proven clinical and biochemical endogenous hyperinsulinemic hypoglycemia.
  
  
  METHODS
  (111)In-DOTA-exendin-4 was administered iv at a dose of about 90 MBq (30 microg peptide) over 5 min. Whole-body planar images of the abdomen were performed at 20 min, 4 h, 23 h, 96 h, and up to 168 h after injection. After surgical removal of the insulinomas, GLP-1R expression was assessed in the tumor tissue in vitro by GLP-1R autoradiography.
  
  
  METHODS
  The detection rate of insulinomas was measured.
  
  
  RESULTS
  In all six cases, the GLP-1R scans successfully detected the insulinomas identified using conventional methods in four cases. By using a gamma-probe intraoperatively, GLP-1R detection permitted a successful surgical removal of the tumors in all patients, diagnosed histopathologically as five pancreatic and one extrapancreatic insulinomas. In vitro GLP-1R autoradiography showed a high density of GLP-1R in all tested insulinomas.
  
  
  CONCLUSIONS
  In vivo GLP-1R imaging is an innovative, noninvasive diagnostic approach that successfully localizes small insulinomas pre- and intraoperatively and that may in the future affect the strategy of insulinoma localization.
authors.affiliation: Division of Endocrinology, Inselspital, University Hospital of Bern, CH-3010 Bern, Switzerland.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Christ
authors.forename: Damian
authors.initials: D
authors.lastname: Wild
authors.forename: Flavio
authors.initials: F
authors.lastname: Forrer
authors.forename: Michael
authors.initials: M
authors.lastname: Brändle
authors.forename: Rahel
authors.initials: R
authors.lastname: Sahli
authors.forename: Thomas
authors.initials: T
authors.lastname: Clerici
authors.forename: Beat
authors.initials: B
authors.lastname: Gloor
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Martius
authors.forename: Helmut
authors.initials: H
authors.lastname: Maecke
authors.forename: Jean Claude
authors.initials: JC
authors.lastname: Reubi
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D000067757:Glucagon-Like Peptide-1 Receptor; D006801:Humans; D007205:Indium Radioisotopes; D007340:Insulinoma / Q000000981:diagnostic imaging*; D007553:Isotope Labeling / Q000379:methods; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging*; D011877:Radionuclide Imaging; D018027:Receptors, Glucagon / Q000032:analysis*; D012680:Sensitivity and Specificity
chemical_list: C000593833:GLP1R protein, human; D000067757:Glucagon-Like Peptide-1 Receptor; D007205:Indium Radioisotopes; D018027:Receptors, Glucagon