ABSTRACT
Key points 66 Bibliography 66
Clinical radiobiology is concerned with the relationship between a given physical absorbed dose and the resulting biological response and with the factors that influence this relationship. Although the term tolerance is frequently (mis-)used when discussing radiotherapy toxicity, it is important to realize that there is no dose below which the complication rate is zero: there is no clear-cut limit of tolerance. What is seen in clinical practice is a broad range of doses where the risk of a specific radiation reaction increases from 0 per cent towards 100 per cent with increasing dose (i.e. a dose-response relationship).
