Evaluation of 131/123I-5-iodo-2′-deoxycytidine as a novel proliferation probe in a tumor mouse model

Abstract This study evaluated a radioiodinated deoxycytidine analog, 131 I-5-iodo-2′-deoxycytidine ([ 131 I]ICdR), as a novel proliferation probe and compared it with 131 I-5-iodo-2′-deoxyuridine ([ 131 I]IUdR) in a NG4TL4 sarcoma-bearing mouse model. As an imaging agent, the biological characteristics of [ 123 I]IUdR is not satisfactory due to its metabolic instability and short biological half-life in vivo. With [ 123 I]ICdR/SPECT it was possible to clearly delineate the tumor lesion at 1 h post-injection (tumor-to-muscle ratio 7.74) in tumor-bearing mice. The results of biodistribution were consistent with those observed in scintigraphic imaging. This study demonstrated that [ 131 I]ICdR is a more promising SPECT probe than [ 131 I]IUdR for imaging proliferation.