title: The role of 99mTc-depreotide in the management of neuroendocrine tumours.
abstract: BACKGROUND
  In-pentetreotide scan (OctreoScan) is a widely available agent with high sensitivity for imaging neuroendocrine tumours. Negative In-pentetreotide poses diagnostic as well as therapeutic problems in terms of staging and consideration of targeted radionuclide therapy.
  
  
  OBJECTIVE
  To assess the role of Tc-depreotide in patients with negative or weakly positive OctreoScan (Krenning score< or =1; measured on a scale range 0-4). To determine the usefulness of Tc-depreotide scintigraphy for highlighting lesions that may be missed by OctreoScan and/or CT/MRI imaging.
  
  
  METHODS
  Prospective analysis of 25 patients with neuroendocrine tumours, with negative or weakly positive In-pentetreotide scans, who were consecutively enrolled to undergo In-pentetreotide and Tc-depreotide imaging. The results were compared with either CT or MRI scans.
  
  
  RESULTS
  Histology was available for 20 of 25 patients: of these 40% had high-grade tumours (cellular proliferation marker Ki-67 score >20%), a further 35% had intermediate-grade tumours (Ki-67 2-20%), and the remaining 25% had low-grade tumours (Ki-67 <2%). Fifty-two percent of patients had completely negative and 48% had weakly positive OctreoScan results. Thirty-two percent of these same patients had significantly positive Tc-depreotide scans (Krenning score> or =2), with the histology demonstrating intermediate-grade or high-grade tumours.
  
  
  CONCLUSIONS
  Tc-depreotide imaging has low sensitivity but is useful in a one-third of OctreoScan-negative patients, displaying significantly better uptake than In-pentetreotide in this patient group. It aids diagnosis by highlighting lesions not seen by OctreoScan and/or CT/MRI imaging, and can possibly identify a group of patients amenable to therapy with radionuclide agents, such as SOM230, targeting somatostatin receptor subtypes 2, 3 and 5.
authors.affiliation: Department of Gastroenterology, Royal Free Hospital, Pond Street, London, UK.
authors.forename: Tahir
authors.initials: T
authors.lastname: Shah
authors.forename: Ilona
authors.initials: I
authors.lastname: Kulakiene
authors.forename: Ann-Marie
authors.initials: AM
authors.lastname: Quigley
authors.forename: Victoria S
authors.initials: VS
authors.lastname: Warbey
authors.forename: Rajaventhan
authors.initials: R
authors.lastname: Srirajaskanthan
authors.forename: Christos
authors.initials: C
authors.lastname: Toumpanakis
authors.forename: Daniel
authors.initials: D
authors.lastname: Hochhauser
authors.forename: John
authors.initials: J
authors.lastname: Buscombe
authors.forename: Martyn E
authors.initials: ME
authors.lastname: Caplin
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013004:Somatostatin / Q000031:analogs & derivatives*
chemical_list: D019275:Radiopharmaceuticals; D013004:Somatostatin; C081788:pentetreotide