Radiotherapeutic implications of genetic instability of tumor cells

A mathematical model was used to explore the radiotherapeutic implications of genetic instability. The model included two populations whose different radiosensitivity was represented by different values of alpha parameter of linear quadratic model. It was shown that the presence of a small fraction of mutants may profoundly affect an optimal treatment schedule structure, especially for radiosensitive tumors currently deemed suitable for treatment by hyperfractionation. In some cases, the analysis favors hypofractionation or hybrid schedules composed of hyperfractionated and hypofractionated phases

Application and limitations of the linear-quadratic survival curve alpha/Beta ratio in selection of radiotherapeutic treatment schedules

This paper dealt with special situations in which limited information may suffice to select between alternative treatment schedules. It was shown that selection between any two schedules might be made on the basis of no more than knowledge of the linear-quadratic model alpha/beta ratio for tumors cells and critical normal tissue in the following circumstances. 1] When the schedules, being compared, are given in the same overall time. 2] When the schedules, being compared, are given in the same overall time, but the schedule of shorter duration has a smaller fraction size. These are shown to be the only circumstances in which knowledge of the alpha/beta ratio alone is sufficient to allow schedule selection. In all other circumstances, some knowledge will be required of the absolute values of alpha and beta as well as kinetic parameters relating to tumor repopulation