Effects of dose-rate and protraction: a symposium. I. Patterns of response to whole-body irradiation: the effect of dose intensity and exposure time on duration of life and tumour production.

Abstract

There seems to be a basic difference of approach between those who are trying to improve radiotherapy and those who are trying to understand the ways in which unwanted exposure to radiation can lead to harm. The aim of the therapist is often to destroy something selectively, be it a malignant tumour or some other pathological process, and what matters is how completely the pathological lesion can be eradicated. The basic mechanisms which are of fundamental importance are the mechanisms by which radiation kills cells or prevents their further division, whether by interfering with their ability to survive the ordeal of mitosis (Spear, 1953) or by changing their habit of growth in the direction of increasing differentiation (Glücksman, 1952). When considering the harmful effect of unwanted irradiation, however, it is not of primary importance what the mechanisms of cell death or of interference with cell division are, or how many cells are so affected, provided that some cells survive and can multiply to replace those which are missing. The survival and multiplication are the primarily important phenomena and these are basic physiological properties which may not be directly affected by the radiation exposure at all. This is the most striking lesson to be learnt from experimental work with single large doses of radiation where the patterns of response of different organs, such as intestine, bone marrow, testes and ovary, depend so clearly on their intrinsic physiological properties.