Analysis of the rate of expression of radiation-induced renal damage and the effects of hyperfractionation.
The response of mouse kidneys to multifractionation irradiation using the [51Cr]EDTA clearance method was re-analysed. As previously published, a series of schedules was investigated giving 1,2,4,8,16,32 and 64 equal X-ray doses in an overall treatment time of 3 weeks, using doses per fraction in the range of 0.9 to 17 Gy. The kidney function was assessed from 19 to 55 weeks after irradiation. The decrease of the clearance with time could be characterized by a new, relevant parameter: the relative rate constant for the development of late damage. These rate constants showed well defined dose-response relationships for each fractionation schedule with an estimated maximum rate constant of 0.15 wk-1. Making use of the logistic transformation of the relative rate constant data, the validity of the linear-quadratic (LQ) model was tested directly using proper statistical methods. We showed that only the higher fraction number data (16,32 and 64) could be described by the LQ-model (alpha/beta = 5.0 +/- 0.5 Gy). The deviations from the LQ-model could not be explained by incomplete or slow repair and we concluded that the expression of the clonogenic survival of target cells in the kidney is not sufficiently described by a linear and a quadratic term.
J V
JV
Lebesque
F A
FA
Stewart
A A
AA
Hart
D000818:Animals; D002860:Chromium Radioisotopes; D004307:Dose-Response Relationship, Radiation; D005260:Female; D007668:Kidney / Q000503:physiopathology / Q000528:radiation effects*; D007678:Kidney Glomerulus / Q000503:physiopathology; D008433:Mathematics; D051379:Mice; D008808:Mice, Inbred CBA; D008954:Models, Biological; D008962:Models, Theoretical; D011878:Radiotherapy / Q000009:adverse effects*
D002860:Chromium Radioisotopes