MULTIPLE DAILY FRACTIONATION IN RADIOTHERAPY - BIOLOGICAL RATIONALE AND PRELIMINARY CLINICAL-EXPERIENCES

The biological bases of radiation dose fractionation are reviewed and discussed with special emphasis on reassortment. Experimental data on animal model systems are presented to clarify that reassortment has to be added to sublethal damage repair and reoxygenation in establishing the rationale for an optimized radiotherapy course according to tumor cell kinetics. Clinical results on several human tumors treated with twice or thrice daily fractions are described. These results show that some clinically radioresistant" tumors (especially if not characterized by a relatively long clinical doubling time) can be satisfactorily dealt with multiple daily fractionation. Our clinical observations indicate that a relatively high cumulative daily dose (200 + 150 + 150 rad) can be safely administered. © 1979."