Impact of the position of a gap on the response of the R1H-tumor of the rat on fractionated split-course radiotherapy

Background: Gaps are a common feature of clinical radiotherapy. Only little information is available about the influence of the position of a gap on t umor response. Material and Methods: In a rodent tumor model (rhabdomyosarcoma R1H of the rat) three split-course schedules were carried out by inserting a 2-week ga p either after the 1st, the 3rd, or the 5th week into a standard schedule o f 30 fractions in 6 weeks. For comparison a standard and an accelerated tre atment were carried out. Result and Conclusion: The position of the gap was found to have a signific ant influence on the tumor response (p = 0.018).