Preliminary In Vivo Evaluation of [131I]-2-Iodo-D-Phenylalanine as a Potential Radionuclide Therapeutic Agent in R1M-Fluc Rhabdomyosarcoma Tumor-Bearing NuNu Mice Using Bioluminescent Imaging

Background: Carrier-added [I-123]-2-iodo-D-phenylalanine (CA [I-123]-2-I-D-Phe) was previously found to have a preferential retention in tumors with a high tumor background contrast in animal models. A previous human dosimetry study demonstrated a favorable biodistribution and radiation burden in human subjects. Aim: The aim of this study was to investigate the potential of CA [I-131]-2-I-D-Phe as an agent for radionuclide therapy. Methods: Sixty (60) nude athymic mice were inoculated subcutaneously with firefly luciferase-transduced R1M rhabdomyosarcoma cells. The mice in the therapy group were injected intravenously (i.v.) with 148 MBq [I-131]-2-I-D-Phe (432 GBq/mmol) in kit solution. Controls were injected with kit solution without radioactivity, with physiological saline, or with 148 MBq [I-131](-) in physiological saline. Tumor growth was quantified using bioluminescent imaging and caliper measurements. Results: [I-131]-2-I-d-Phe clearly reduced tumor growth in the treated mice compared with the control groups. A tumor growth-rate reduction of at least 33% was found for mice receiving a therapeutic dose. There were no serious adverse side-effects of the therapy. Conclusions: In conclusion, i.v. injection of CA 148 MBq [I-131]-2-I-d-Phe specifically reduces tumor growth in athymic nude mice without relevant side-effects on the animals' health.