The Effect of Oxygen on the Sensitivity of Mammalian Tumour Cells to Neutrons and X-rays

Summary

Telophase abnormalities in Ehrlich ascites-tumour cells were observed 18 hours after the cells had been irradiated either with 1·5 mev x-rays or fast neutrons. The sensitivity of well-oxygenated tumour was greater than that of anoxic tumour by a factor of 2·5 in the case of x-rays, but of only 1·3 in the case of neutrons. After neutron-irradiation the abnormalities showed an exponential relationship to dose, but after x-irradiation the abnormalities increased more rapidly than the first power of the dose. When the proportion of abnormalities was 50 per cent the RBE in O₂ was 3·2, but in N₂ it was 6·5.