A transplantation assay method has been developed for studies of cell survival in solid adenocarcinomas of mice irradiated in vivo. The assay depends on the inverse relationship between the time from grafting until tumors are first palpable and the logarithm of the volume of viable tumor cells inoculated. In the current experiments, sources of variation in the procedure were examined, and D37 values were determined for Adenocarcinoma 755 and Adenocarcinoma MTG-B irradiated in vivo with 137Cs-γ-rays. The D37 of MTG-B tumor cells irradiated in situ indead mice was also determined. The data suggest that D37 values for such tumor cells irradiated in vivo reflect the sensitivity of a relatively resistant, anoxic fraction which comprises a minority of the tumor cell population. Radiation damage to the larger fraction of cells that were more sensitive and presumably beHer oxygenated was not reflected in the observed Da7 values, but was interpreted as affecting the lower extrapolation number of the mixed cell population. These studies demonstrate that the lcinetics of the acute cytolethal response of solid carcinoma cells irradiated in vivo are similar to those of free cell tumor and culture systems.
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Clifton et al. (1966) studied this question.