The demonstration of in vivo misonidazole tumour toxicity using post radiation hypoxia

The cytotoxic effect of the radiosensitizer misonidazole on hypoxic tumour cells in vivo has been studied. Using standard procedures of large single doses of X-ray (30 Gy) followed by 1.0 mg/g misonidazole, no significant cytotoxicity (measured by tumour regrowth) could be observed. In contrast, when utilizing post radiation hypoxia (3 h of 7% oxygen breathing) in conjunction with post radiation misonidazole, an increased amount of direct drug toxicity was demonstrated. The use of this acute hypoxia treatment may prove to be a useful tool for measuring various in vivo radiobiological responses.