Effect of a Single Dose of Radiation on Proportion of Hypoxic Cells in a C3H Mouse Mammary Carcinoma

Abstract

Radiation dose-tumor control response assays were completed on a C3H/He mouse mammary carcinoma irradiated at a volume of 250 mm3. Radiation was administered either as a single dose or as 2 doses with an intertreat-ment interval of 5 days. For single-dose irradiation, the ratio [image] was 1.1, i.e., O2 30 psi was of only minor effect in altering tumor control probability. For the 2nd set of assays, the first dose of radiation was 3000 rads, administered under O2 30 psi, so that the only surviving cells would have been hypoxic at the time of treatment. Five days later the 2nd and variable dose was administered either under hypoxia, air, or O2 30 psi conditions. In this instance, the ratio [image] was 2.7. These results were interpreted as strongly indicating that in the 5-day interval between treatments there was a drastic change in accessibility of oxygen to the tumor all during respiration of oxygen at 30 psi.