5-[¹²⁵I]IODO-2'-Deoxyuridine in the Radiotherapy of Solid CNS Tumors in Rats

Abstract

We have been investigating the therapeutic efficacy of the thymidine analog 5-iodo-2 -deoxyuridine (IUdR) when radiolabeled with the Auger electron emitter ¹²⁵I in rats bearing intrathecal (i. t.) or intracerebral (i. c.) 9L gliosarcoma solid tumors. [¹²⁵I]IUdR was infused i. t. (via subarachnoid catheters) or intracerebrally over a 5- or 2-day period; equimolar concentrations of [¹²⁷I]IUdR were infused into control animals. Hind-leg paralysis and/or survival were followed over time. The results indicate that compared with [¹²⁷I]IUdR, rats bearing intrathecal tumors and infused i. t. with [¹²⁵I]IUdR showed significant prolongation of the onset of median paralysis (15.2 versus 9 days). Similarly, the median survival of rats bearing intracerebral tumors and infused i. c. with [¹²⁵I]IUdR was significantly increased (24 versus 17 days). The data substantiate the antineoplastic potential of [¹²⁵I]IUdR and indicate a promising role for this radiopharmaceutical in the treatment of CNS cancers.