[Minimal effective dose of perfluorochemical emulsion as a radiosensitizer]

Perfluorochemical emulsion can dissolve large amount of oxygen, carry it into tissues, and consequently enhance the response of hypoxic tumor cells to radiation. Previously we reported on the radiosensitizing effect of perfluorochemical emulsion. In the present study, the minimal effective dose of Fluosol-DA Saline 20% (FDAS), one of preparations of perfluorochemical emulsion, was determined. Mice bearing Lewis lung carcinoma in their thighs were injected in single i.v. of FDAS (1.25-20 ml/kg) and were allowed to breath carbogen (95% O2 + 5% CO2) for 30 min. before and during irradiation (15 Gy). The effect of FDAS was measured by the growth delay of the treated tumor. Administration of FDAS at over 5 ml/kg together with carbogen breathing significantly (p less than 0.01) enhanced the tumor growth delay as compared with treatment of carbogen breathing without FDAS. There was a significant difference (p less than 0.05) in the radiosensitizing effect between injection of FDAS at 5 ml/kg and 20 ml/kg, while there were not significant differences between injection of FDAS at 5 ml/kg and 10 ml/kg, or 10 ml/kg and 20 ml/kg, respectively. These results indicate that the minimal effective dose of FDAS is 5 ml/kg, which could be applied to clinical fractionated irradiation therapy as a standard FDAS-dose.