title: Influence of the timing of a concomitant boost during fractionated irradiation of rat rhabdomyosarcoma R1H.
abstract: Rhabdomyosarcomas R1H of the rat (WAG/Rij) were treated using fractionation schedules including a boost. The total dose was 60 Gy. Overall treatment time was 6 weeks. Four different boost schedules were applied: a single dose boost (12.15 Gy) at the last day of treatment, a single dose boost (12.15 Gy) at the first day of treatment, a schedule including the boost in 7 fractions during the first week, and a schedule including the boost in 10 fractions during the first week of treatment. A standard schedule with 30 fractions of 2 Gy without a boost was used for comparison. Initially accelerated schedules, i.e. those with a boost at start of treatment, revealed higher effect on tumour parenchyma as monitored by local control rate and net growth delay. This could be due to a decrease of radio-sensitivity, that is, an increase of the hypoxic fraction of clonogenic tumour cells during fractionated irradiation.
authors: Institute of Biophysics and Radiobiology, University of Hamburg, Germany.
authors: H H
authors: HH
authors: Dubben
authors: H P
authors: HP
authors: Beck-Bornholdt
mesh_terms: D000818:Animals; D008297:Male; D009368:Neoplasm Transplantation; D011879:Radiotherapy Dosage; D051381:Rats; D012208:Rhabdomyosarcoma / Q000473:pathology / Q000532:radiotherapy*; D013997:Time Factors