Correspondence

Abstract

Mr. W. E. Liversage was kind enough to show us in advance a copy of his letter which appears in this issue of the journal so that we may make a few comments. We would like to place on record that we think he has quoted our results fairly and accurately, and we would agree with his overall conclusion that in a situation where our experimental findings are applicable, then one would expect to find a lowered O.E.R. for a high dose-rate fractionated regime as well as for a low dose-rate continuous exposure treatment. There are, however, two areas where we disagree: the first is a philosophical point and is a question of how far one should go in applying radiobiological data to radiotherapy, and the second is that we consider the pooling of data in Figs. 1 and 2 of his letter to be misleading. Firstly the whole basis of the reasoning of Liversage is the statement in the first paragraph of his letter that the findings of Hall and Cavanagh (1967) “are of considerable significance to clinical radiotherapists”. This we believe to be an overstatement of the case. Our results were obtained with a simple basic radiobiological test system (seedlings of Vicia faba) in which extreme hypoxia was precisely defined to be the presence of less than 10 p.p.m. of oxygen.