Studies in Optimum Dosage—The Mackenzie Davidson Memorial Lecture

Abstract

I have chosen as title “Studies in Optimum Dosage” because the general problem of choice of dosage is a subject to which I have been giving some thought recently. I hope that it will stimulate your curiosity enough to persuade you to consider study of like problems. Over the last ten years, and that despite the war, we have made substantial advances in technique—beam direction, rotation therapy, improved X-ray plant, and numerous ingenious devices for use with radium and radioisotopes. The same ten years—perhaps one might even say twenty years—have seen substantial advance in the accuracy of methods of assessing dose, and of giving any predetermined dose. In this field particularly, radiotherapists owe a great debt to the physicists. We have perhaps been so proudly conscious of improvement in these fields as to be blind to the slenderness of the scientific evidence on which we base decisions as to the actual dose to give in any particular case or group of cases. In that aspect of radiotherapy we have still barely left the realms of pure empiricism. If radiotherapists are asked just why they give such and such a dosage they will give quite a variety of replies. Some will say that that is what they have been taught in the London D.M.R.T.; others that it seems to work quite well; and others that they know it is safe.