Abstract
Purpose. To analyze the possibility of reducing the number of fractions but maintaining the full biological effect of radiotherapy by varying the dose per fraction.
Methods. An arbitrary treatment with a constant dose per fraction is substituted for a fully isoeffective combination of a hyperfractionated and hypofractionated treatment. The number of fractions of the combined treatment is derived. All calculations are based on the linear-quadratic model.
Conclusions. Standard uniform fractionation requires the fewest fractions. Any variation in dose per fraction increases the number of fractions of a fully isoeffective treatment.