Radiotherapy of the rhabdomyosarcoma R1H of the rat: influence of the time interval between two daily fractions during hyperfractionated radiotherapy.

TY - JOUR

T1 - Radiotherapy of the rhabdomyosarcoma R1H of the rat: influence of the time interval between two daily fractions during hyperfractionated radiotherapy.

AU - Kleineidam, M

AU - Pieconka, A

AU - Beck-Bornholdt, Hans-Peter

PY - 1994

Y1 - 1994

N2 - The response of the rhabdomyosarcoma R1H of the rat to hyperfractionated irradiation with different time intervals between the two daily fractions has been investigated. All tumours were exposed to irradiation 5 days per week over 6 weeks. A standard treatment of 30 fractions, i.e. one fraction per day, of 1.83-2.75 Gy (200 kVp X-rays) was compared with a hyperfractionated schedule of 60 fractions, i.e. two fractions per day, of 0.92-1.38 Gy with time intervals of either 1, 2, 3, 5 or 6 h between the two daily fractions. Tumour response has been assessed by (a) net growth delay and (b) local tumour control. Compared with standard treatment (one fraction per day) significant reduction (p <0.005) of net growth delay was observed for the tumours treated with two daily fractions separated by 2 h. However, at a time interval of 5 and 6 h between the two daily fractions net growth delay increased considerably (p <0.0001 and p <0.01) as compared with the standard treatment and an increased rate of local tumour control was observed. The major findings is that tumour response is not as would be predicted by repair if the interval between the two daily fractions exceeds 2 h. The competing or overriding mechanisms cannot be identified ultimately, but the data, though based on small animal numbers and collected over an extended time period, reflect a significant effect.

AB - The response of the rhabdomyosarcoma R1H of the rat to hyperfractionated irradiation with different time intervals between the two daily fractions has been investigated. All tumours were exposed to irradiation 5 days per week over 6 weeks. A standard treatment of 30 fractions, i.e. one fraction per day, of 1.83-2.75 Gy (200 kVp X-rays) was compared with a hyperfractionated schedule of 60 fractions, i.e. two fractions per day, of 0.92-1.38 Gy with time intervals of either 1, 2, 3, 5 or 6 h between the two daily fractions. Tumour response has been assessed by (a) net growth delay and (b) local tumour control. Compared with standard treatment (one fraction per day) significant reduction (p <0.005) of net growth delay was observed for the tumours treated with two daily fractions separated by 2 h. However, at a time interval of 5 and 6 h between the two daily fractions net growth delay increased considerably (p <0.0001 and p <0.01) as compared with the standard treatment and an increased rate of local tumour control was observed. The major findings is that tumour response is not as would be predicted by repair if the interval between the two daily fractions exceeds 2 h. The competing or overriding mechanisms cannot be identified ultimately, but the data, though based on small animal numbers and collected over an extended time period, reflect a significant effect.

M3 - SCORING: Zeitschriftenaufsatz

VL - 30

SP - 128

EP - 132

JO - RADIOTHER ONCOL

JF - RADIOTHER ONCOL

SN - 0167-8140

IS - 2

M1 - 2

ER -