Comparison of intravenous and intra-arterial pyrimidine infusion as a means of radiosensitizing tumors in vivo.

The halogenated pyrimidine analogue 5-bromo-2-deoxycytidine (BCdR) was infused into BALB/C mice bearing EMT-6 tumors via either the intravenous or intra-arterial route. Hepatic dehalogenation of the drug was blocked by 5-diazouracil (DAZU) in order to ascertain its relative importance in the degradation of intravenously administered analogues. Increased radiosensitization was noted with higher intravenous pyrimidine concentrations, but DAZU blockage of dehalogenation had little effect. These studies show that following intravenous infusion, enough BCdR apparently bypasses the hepatic vessels to permit tumor radiosensitization despite dilution of the drug by the systemic circulation.