Quantitative evaluation of the radiosensitivity of cells of a transplantable rhabdomyosarcoma in the rat
article
Using an improved cell dispersion technique, survival curves have been obtained for X-irradiated cells of a transplantable solid rat tumour (rhabdomyosarcoma). Variable doses of irradiated or non-irradiated tumour cells were inoculated into isologous recipients. The non-irradiated (control) ED50 calculated according to the method of Litchfield and Wilcoxon varied from 32 cells to 13·5 cells for the different experiments. The results show that the D37 of the anoxic cell survival curve (irradiation in the dead animal with doses from 480-3840 rad) is about 380 rad, the extrapolation number N is approximately 10. An oxygen enhancement ratio of 3 was found. Comparison of these figures with results obtained by others with a murine leukaemia suggests that the D37 of the survival curves for cells from radiosensitive and radioresistant tumours are similar, the extrapolation number probably being different. By delivering doses between 480-3840 rad to small tumours with an average weight of 0·4 g (containing 2 × 108 cells) in the living non-anaesthetized animals, the survival curve of the in vivo tumour was estimated. From the shape of the various curves it was deduced that 15 per cent of the cells of these small tumours has probably been in an anoxic state at the time of irradiation. This proportion of anoxic cells, together with a rather high extrapolation number, provide a satisfactory explanation for the radioresistance of this type of tumour. © 1966.
Topics
TNO Identifier
226916
ISSN
00142964
Source
European Journal of Cancer, 2(1), pp. 33-34,IN7,35-42.
Pages
33-34,IN7,35-42
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