Somatostatin receptor expression in the kidney: Can uptake be reduced by cold octreotide? Preliminary results from a clinical study using Ga-68 DOTA-NOC receptor PET/CT

Abstract

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Objectives: Renal uptake of somatostatin receptor analogs is mediated mainly by the megalin dependent pathway. Reubi et al. have shown that there is high expression of sstr2 in the vasa recta of human kidney and to a lesser extent in the cortical tubules. Ga-68-DOTA-NOC has a very high specificity/affinity for sstr2,3 and 5. The aim of this study was to determine if octreotide therapy (sandostatin) decrease the renal uptake of somatostatin analogs.

Methods: Two groups of patients with metastasized neuroendocrine tumors were selected: GrA comprised 12 patients (mean age 56 yr; 40-70 yr) on sandostatin within 6 weeks prior to receptor PET/CT, and GrB 20 patients (mean age 58 yr; 38-73) off sandostatin. Receptor PET/CT was performed after injection of 100 MBq of Ga-68-DOTA-NOC. SUVmax of left and right kidney cortex was calculated in the two groups and independent sample T test was performed.

Results: The SUVmax of left/right kidney cortex in patients on sandostatin (GrA) was 11.3/10.7 and was somewhat higher (13.4/13.5) in GrB. There was a significant difference in the mean of SUVmax (15%, p<0.005) in patients on sandostatin therapy as compared to patients without octreotide treatment.

Conclusions: As somatostatin receptors are present in the kidney cortex/medulla, low dose octreotide therapy may be effective in reducing renal uptake of sstr targeting peptides and thus diminish the nephrotoxicity of Peptide Receptor Radionuclide Therapy.