Fractionation with X rays and neutrons in mice: response of skin and C3H mammary tumours

Publisher Website
Google Scholar
Abstract
The effectiveness of fast neutron therapy was tested where it was unlikely to show any advantage relative to conventional X rays, i.e. on a mouse mammary tumour which contains radioresistant hypoxic cells, but which reoxygenates extensively after a large X-ray dose. The therapeutic effects were estimated by comparing the degree of early skin reaction associated with a standard frequency of local tumour control assessed at 150 days. Five and nine fractions of X rays or fast neutrons were given at the expected optimum spacing for re-oxygenation after X rays. Single doses were also used. Five fractions of X rays given in nine days were indeed found to be as effective as either of the fractionated neutron treatments, which were closely similar to each other, but nine fractions of X rays in 18 days were considerably less effective. These results suggest that X rays can be made as effective as fast neutrons, by a sharply optimal choice of fractionation dose and interval. However, to make this choice requires detailed knowledge of the time course of re-oxygenation in the tumour to be irradiated. The fractionation schedule with fast neutrons appears to be much less critical.
Keywords