Keynote address: the scientific basis of the present and future practice of clinical radiotherapy.

At mid-century radiotherapy was more an art than a science, but is presently based on radiobiological parameters and cell kinetics. This close interaction between basic scientific principles and clinical practice has been made possible because one can correlate quantitatively doses of irradiation with observed responses. First, a short historical review will be made because it gives a perspective for the understanding both of progress made and prevailing misconceptions. The important radiobiological parameters and cell kinetics will then be discussed in some detail to demonstrate that they should be thoroughly understood in their relationship to radiotherapy. The overall treatment planning must be based on the clinical applications of the main radiobiological parameters. The combined treatment with surgery, either pre- or postoperatively, and multiple daily fractionations will be used as examples. The teaching of radiobiology should be considerably expanded, not only for its own scientific merit but also to show how it applies to clinical situations. This should be reflected in the expansion of the board examination.