Differences in repopulation kinetics in mouse skin during split course multiple fractions per day (MFD) or daily...

The influence of protraction and distribution of irradiation as a function of time on the repopulation kinetics of mouse skin have been evaluated. Twenty fractions have been given either daily for 5 days per week during 4 weeks, or thrice a day to 10 irradiations in 3 days, repeated after a rest period of 19 days, resulting also in an overall time of 4 weeks. The acute skin reaction was scored. It was found that the split course multiple fractions per day (MFD) schedule induced less skin reaction than continuous daily fractionation, which was mainly attributable to recovery of skin damage during the rest period. Therefore, it can be postulated that the repopulation of the surviving clonogenic epidermal cells is less efficient during continuous daily irradiation than during split course MFD schedule given in the same overall treatment time.