Misonidazole Enhancement of Radiation-induced Growth Delay in Rat Rhabdomyosarcoma Tumours Exposed to Accelerated Carbon and Neon Ions

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Abstract
The response of a rat rhabdomyosarcoma was assessed by measurements of radiation-induced growth delay resulting from administration of the hypoxic cell sensitizer misonidazole in combination with single and fractionated doses of X-rays and charged-particle radiation. Enhancement ratios of 1.8-2.1 were obtained following single doses of misonidazole (500 mg/kg i.p.) and 225 kV X-rays. Single doses of misonidazole with either C-ion or Ne-ion radiation in the 4-cm extended-peak ionization region led to enhancement ratios of 1.2-1.3. When combined misonidazole (300 mg/kg i.p.) and X-ray treatments were given in 4 daily fractions the enhancement ratios decreased to 1.2-1.5. A 4-fraction schedule using either C-ion or Ne-ion radiation in combination with misonidazole gave enhancement ratios of 1.1-1.3, which are similar to the values obtained for single-dose schedules with the sensitizer and charged-particle radiation.