Somatostatin receptor subtype 2-mediated uptake of radiolabelled somatostatin analogues in the human kidney.
OBJECTIVE
Renal irradiation is a dose-limiting factor in peptide receptor radionuclide therapy using radiolabelled somatostatin analogues. This irradiation is mainly caused by reabsorption of radiolabelled peptides in the proximal tubule. In the human kidney, somatostatin receptors are expressed in the vasa recta, tubuli and glomeruli. It is not clear to what extent these receptors contribute to the total kidney radioactivity uptake.


METHODS
Retrospectively, [(111)In-DTPA(0)]octreotide scans of ten selected patients with carcinoids (well-differentiated gastrointestinal endocrine tumour) with liver metastases were evaluated. For each patient, two scans were obtained: one scan was performed without (control) and one during treatment with unlabelled octreotide. Kidney, tumour, spleen and liver uptake was measured in both scans.


RESULTS
The interval between the two scans per patient varied from 50 to 397 days. Octreotide treatment substantially lowered kidney [(111)In-DTPA(0)]octreotide uptake in eight out of ten patients. Kidney uptake in all patients was reduced to 82%+/-15% of control, (p < 0.01). A correlation between kidney uptake and spleen uptake was found (r=0.67, p < 0.05). Serum creatinine was unchanged. Surprisingly, tumour and liver [(111)In-DTPA(0)]octreotide uptake was not significantly influenced by unlabelled octreotide therapy, but spleen uptake was significantly lowered by treatment (30.6% of control, p < 0.002).


CONCLUSIONS
We conclude that the somatostatin receptor plays a role in the total renal uptake of radiolabelled somatostatin analogues. The long interval between scans might explain the finding that tumour and liver metastasis uptake of [(111)In-DTPA(0)]octreotide was unchanged. Further studies are needed to confirm and eludicate the results of this study.
Rolleman
Edgar J
EJ
Department of Nuclear Medicine, Erasmus MC, Room L244, 's Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands. e.rolleman@erasmusmc.nl
Kooij
Peter P M
PP
de Herder
Wouter W
WW
Valkema
Roelf
R
Krenning
Eric P
EP
de Jong
Marion
M
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging / Q000378:metabolism*; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D015282:Octreotide / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D009928:Organ Specificity; D004369:Pentetic Acid / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D017481:Receptors, Somatostatin / Q000378:metabolism*; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics*; D014018:Tissue Distribution
C497824:111In-octreotide, DTPA(0)-; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; D013004:Somatostatin; D004369:Pentetic Acid; C093733:somatostatin receptor 2; D015282:Octreotide