Biokinetics of 111In-DTPA-D-Phe1-octreotide in nude mice transplanted with a human carcinoid tumor

The long time biokinetics of the radiolabeled somatostatin analogues In-111-DTPA-D-Phe(1)-octreotide was studied in nude mice transplanted with the human carcinoid tumor, GOT1. The results were compared with those from the patient with the original tumor. This patient has been diagnosed and later treated with In-111-DTPA-D-Phe(1)-octreotide. The animals received about 2 MBq In-111-DTPA-D-Phe(1)-octreotide (0.1 mug) by injection into a tail vein. The animals were killed 0.5 h-14 d after injection of the radiopharmaceutical. Tumor tissue and normal tissues were collected and weighed and measured for In-111 activity. The In-111 uptake in the tumor was higher than in all normal tissues except the kidneys, The tumor-to-normal-tissue activity concentration, TNC, increased with time for all normal tissues studied. These data were similar to those observed for the original tumor in the patient. The similar biokinetics for In-111-DTPA-D-Phe(1)-octreotide in the tumor-bearing mice and the patient makes this animal model suitable as a model for evaluation of therapy of somatostatin receptor (sstr) expressing tumors with radiolabeled somatostatin analogues. Furthermore, the increase with time of TNC both in mice and the patient indicates that long-lived radionuclides are preferred for therapy with radiolabeled somatostatin analogues. (C) 2001 Elsevier Science Inc. All rights reserved.