Comparison of tumour growth delay with cell survival

Publisher Website
Google Scholar
Abstract
The recent article of McNally (1973) comparing two different means of assaying the radiation response of rat tumours—the growth delay technique and direct assay of cell survival—presented conclusions which, if true, have important implications for radiobiological studies. The data obtained by McNally show that the two techniques give different values not only for the oxygen enhancement ratio (3·0 and 2·5 for the growth delay and cell survival techniques respectively), but also for the “effective proportion” of hypoxic cells in the tumours. The author concludes that techniques which involve removal of cells from their natural environment (such as is involved in measurements of tumour cell survival) may lead to erroneous estimates of their true radiosensitivity. Although we agree that immediate removal of cells from an irradiated tumour may, in some cases, result in an incorrect estimate of the effective survival of those cells (for such reasons as preventing their repair of potentially lethal damage, as well as those discussed by McNally), we believe that the problems inherent in the analysis of tumour growth data to obtain basic radiobiological information are more serious than those met in similar extrapolations of cell survival data.