The role of 99mTc-depreotide in the management of neuroendocrine tumours.
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.
Shah
Tahir
T
Department of Gastroenterology, Royal Free Hospital, Pond Street, London, UK.
Kulakiene
Ilona
I
Quigley
Ann-Marie
AM
Warbey
Victoria S
VS
Srirajaskanthan
Rajaventhan
R
Toumpanakis
Christos
C
Hochhauser
Daniel
D
Buscombe
John
J
Caplin
Martyn E
ME
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*
D019275:Radiopharmaceuticals; D013004:Somatostatin; C081788:pentetreotide