Radiosensitizing effect of misonidazole in fractionated gamma-ray treatment of a human malignant melanoma grown in athymic nude mice.

The effect of the hypoxic cell radiosensitizer misonidazole (Ro-07-0582) has been tested on a human malignant melanoma grown subcutaneously in the athymic mutant nude mouse. A 60Co therapy unit was used for local irradiation of the animals. The tumours were exposed daily to 3.75 Gy (375 rad) over four consecutive days, to a total dose of 15.0 Gy. Misonidazole in doses of 500 mg/kg bodyweight was administered intraperitoneally in the mice 45 minutes before each irradiation. The time necessary for the tumours to regrow to their original sizes was compared with that of tumours treated with four daily fractions of 3.75, 4.50 and 5.25 Gy without sensitizer. The enhancement ratio of misonidazole was found to be 1.05.