UNLABELLED: Somatostatin receptor targeting is a valuable method to treat somatostatin receptor-positive tumours. In peptide receptor radionuclide therapy, it is essential to determine the highest activity that can be safely administered to the patient. As (90)Y emits no gamma rays, absorbed doses for (90)Y are usually estimated using the same peptide labelled with (111)In. The aim of the study was to determine if replacement of (90/88)Y by (111)In affects the biodistribution profile of five selected somatostatin analogues in preclinical experiments. MATERIALS AND METHODS: Radiolabelled peptides were administered intravenously to male Wistar rats. RESULTS: The peptides under study labelled either with (111)In or with (88/90)Y showed similar distribution profiles in all tissues excepting the kidney. The kidney radioactivity uptake was significantly lower for (88/90)Y-labeled peptide in comparison with the one of (111)In. CONCLUSION: We conclude that a radiation-absorbed dose after (90)Y-labelled somatostatin analogues appears to be lower than that predicted by the (111)In-labelled peptide.

Faculty of Pharmacy Charles University Heyrovskeho 1203 CZ 50005 Hradec Kralove Czech Republic