TUMOR-TARGETING POTENTIAL OF RADIOIODINATED IODODEOXYURIDINE IN BLADDER-CANCER

Since bladder cancer arises in the superficial lining of the urotheliu m, it is a likely candidate for site-directed administration of 5-iodo -2'-deoxyuridine radiolabeled with the Auger electron emitter I-123 or I-125 (IUdR). Methods: We instilled *IUdR for 2 hr directly within t he bladder lumen of rats bearing N-methyl-N-nitrosourea (NMU)-induced bladder cancer and conducted scintigraphic, biodistribution and autora diography (ARG) studies 48 hr and 1 wk later. Control animals were not subjected to the carcinogen but were instilled with IUdR. Results: T wo groups of animals were identified after instillation of MNU: Group A consisted of rats with hyperplasia and Group B of rats with papillar y carcinoma (stages Ta and T1). Scintigraphic detection of carcinomas was achieved with high sensitivity and specificity, and increased tumo r-to-normal tissue ratios were obtained in both groups. Moreover, ARG demonstrated that (1) the uptake of IUdR was observed in the hyperpla stic and carcinomatous urothelium but not in the normal urothelium; (2 ) uptake was detected at a very early stage of tumor development (hype rplasia stage); (3) IUdR was able to penetrate deep within the bladde r wall; and (4) other normal dividing tissues, such as the bone marrow , the small intestine and the large intestine, were free of silver gra ins (i.e., no DNA-incorporated IUdR). Conclusion: Since this carrier of Auger electron emitters has antineoplastic effects ([I-123]IUdR and [I-125]IUdR) in addition to its scintigraphic potential ([I-123]IUdR and [I-131]IUdR), it holds promise for therapy and early diagnosis of bladder cancer.