The response of a mouse sarcoma to single and divided doses of x-rays and fast neutrons.

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.