Multiple fractions per day in retrospect; the L-Q model and the tolerance profile.

Multifractionation was about half a century ago used in radiation therapy. This becomes clear from a review of the literature. One case, reported to have been treated by Coutard with multifractionation is discussed in detail. In order to compare the various treatment modalities the authors have plotted the Extrapolated Tolerance Dose (ETD) against the alpha/beta dose (parameters featuring in the linear-quadratic model, L-Q model), and derived the idea of a "tolerance profile". The case treated by Coutard remains closely within the limits of the present day tolerance profile. It remains unclear why multifractionation has disappeared as a treatment modality for 50 years before returning recently.