Abstract
The response of an experimental sarcoma to single doses and two fractions of x-rays and fast neutrons has been investigated to test the hypothesis that slowly shrinking sarcomata will reoxygenate poorly and therefore will benefit more from fractionated neutron treatment than from fractionated x-ray treatment, in contrast with rapidly shrinking carcinomata. Neutrons were approximately three times more effective than x-rays, both for single doses and for two fractions given in 48 hours, when regrowth was used as a measure of response. This observation is closely similar to results previously obtained on a rat fibrosarcoma and contrasts with previous results from a mouse mammary carcinoma, and is in agreement with the hypothesis.
Highlights
MOST animal solid tumours have been found to contain hypoxic cells
Single doses of neutrons have been found to be more effective in damaging such tumours, relative to the effect on normal tissues, than single doses of x or y rays (e.g. Field, Jones and Thomlinson, 1967; Barendsen and Broerse, 1969; Fowler et al, 1972)
A natural process of reoxygenation of these hypoxic cells may occur in the intervals between doses if a fractionated course of irradiation is given (Thomlinson, 1968)
Summary
The CBA sarcoma used in the present experiments (Sarcoma F) was obtained from Hewitt, who has previously described its origin and its use in various radiobiological studies involving measurements of cell survival (Hewitt and Wilson, 1961; Hewitt, 1966). Growth curves were constructed to animals breathing oxygen appear signiby plotting the average value for the geometric ficantly less effective than a single dose, mean diameters of the tumours of a group of mice given the same treatment. 3.-Dose response curves obtained by integrating the area between each tumour regrowth curve and an upper size limit of 12 mm mean diameter (arbitrary units) A similar change from positive to negative occurs with increasing doses of neutrons
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