In vivo use of a radioiodinated somatostatin analogue: dynamics, metabolism, and binding to somatostatin receptor-positive tumors in man.
Somatostatin analogues, labeled with gamma-emitting radionuclides, are of potential value in the localization of somatostatin receptor-positive tumors with gamma camera imaging. We investigated the application in man of a radioiodinated analogue of somatostatin, 123I-Tyr-3-octreotide, which has similar biologic characteristics as the native peptide. The radiopharmaceutical is cleared rapidly from the circulation (up to 85% of the dose after 10 min) mainly by the liver. Liver radioactivity is rapidly excreted into the biliary system. Until 3 hr after injection, radioactivity in the circulation is mainly in the form of 123I-Tyr-3-octreotide. Thereafter, plasma samples contain increasing proportions of free iodide. Similarly, during the first hours after injection, radioactivity in the urine exists mainly in the form of the unchanged peptide. Thereafter, a progressive increase in radioiodide excretion is observed, indicating degradation of the radiopharmaceutical in vivo. Fecal excretion of radioactivity amounts to only a few percent of the dose. The calculated median effective dose equivalent is comparable with values for applications of other 123I-radiopharmaceuticals (0.019 mSv/MBq).
Bakker
W H
WH
Department of Nuclear Medicine, University Hospital Dijkzigt, Rotterdam, The Netherlands.
Krenning
E P
EP
Breeman
W A
WA
Kooij
P P
PP
Reubi
J C
JC
Koper
J W
JW
de Jong
M
M
Laméris
J S
JS
Visser
T J
TJ
Lamberts
S W
SW
D000328:Adult; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D015282:Octreotide / Q000031:analogs & derivatives* / Q000378:metabolism; D011877:Radionuclide Imaging; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D017481:Receptors, Somatostatin
D007457:Iodine Radioisotopes; D017981:Receptors, Neurotransmitter; D017481:Receptors, Somatostatin; C045210:3-Tyr-octreotide; D015282:Octreotide