Radiation fractionation sensitivity of epiphyseal cartilage in a weanling rat model.
Tibial growth at 100 days of age was measured in Sprague-Dawley rats treated at 21 days to the proximal tibia with various courses of fractionated radiation. In split-dose and multiple-fraction experiments, a minimum interval of 5-6 hr was required to achieve maximal sparing of growth arrest. Total doses required to reduce growth to 80% of untreated controls were computed from dose-response curves for fractionated radiation (dose/fraction 1.0-10 Gy). When fitted to a linear-quadratic model of radiation response the data described an estimated alpha/beta of 4.47 (95% C.I. (3.71, 5.23) Gy). This value suggests that the fractionation sensitivity of the epiphyseal plate is substantially greater than that of most neoplasms, predicting a favorable therapeutic gain with the use of hyperfractionated radiation therapy.
Eifel
P J
PJ
University of Texas M. D. Anderson Cancer Center, Houston 77030.
Sampson
C M
CM
Tucker
S L
SL
D000818:Animals; D006132:Growth Plate / Q000528:radiation effects*; D008297:Male; D011829:Radiation Dosage; D011836:Radiation Tolerance; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors