Radiation Resistance and the Dose-Rate Effect: Experimental

Abstract

Prior to 1980 it was widely thought that radiation is a relatively non-specific killing agent, in the sense that it was not possible to attribute success or failure in clinical radiotherapy to differences in the inherent radiosensitivity of tumour cells. For some decades, therefore, radiobiological research has concentrated mainly on hypoxia: it was tacitly believed that failure in treatment is usually related to the presence of hypoxic cells, which are known to be considerably more resistant to low linear energy transfer (LET) radiation than well-oxygenated cells. Reoxygenation of hypoxic cells is known to occur in experimental tumours and one reason for clinical failure could be the failure of a tumour to reoxygenate satisfactorily during a conventional course of radiotherapy.