C. Petersen et al., LINEAR-QUADRATIC ANALYSIS OF TUMOR RESPONSE TO FRACTIONATED RADIOTHERAPY - A STUDY ON HUMAN SQUAMOUS-CELL CARCINOMA XENOGRAFTS, International journal of radiation biology, 73(2), 1998, pp. 197-205
Citations number
49
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Radiology,Nuclear Medicine & Medical Imaging","Biology Miscellaneous
Purpose: To compare values for the alpha/beta ratio in experimental ru
mours irradiated either under conditions of clamping and short overall
lime or under more 'clinically realistic' conditions. Materials and m
ethods: Human squamous cell carcinomas, FaDu and GL, were grown in nud
e mice. alpha/beta values were determined from local tumour control da
ta after treatment with single doses and 2, 4, and 8 fractions under c
lamp hypoxia in 3.5 days, using maximum likelihood analysis. Effective
alpha/beta values (alpha/beta(eff)) were determined from treatment wi
th 12, 30, and 60 fractions under ambient conditions in a constant ove
rall treatment lime of 6 weeks. Results: After correction for an oxyge
n enhancement ratio of 2.7 the alpha/beta values were 15 Gy (95% CI 9;
24) for FaDu and 49 Gy (26; 122) for GL. In FaDu the TCD50 values aft
er 12 to 60 fractions were not significantly different, the alpha/beta
(eff) value was infinite (52; inf.). Unexpected from the high alpha/be
ta value, the TCD50 values of GL rumours increased from 37 Gy (28; 47)
after 12 fractions to 59 Gy (52; 67) after 60 fractions: the alpha/be
ta(eff) value was 3 Gy (0.6; 12 Gy). Conclusions: The results support
the view that mechanisms other than recovery from sublethal radiation
damage and repopulation of clonogenic tumour cells may importantly imp
act on treatment outcome when the number of fractions is changed in cl
inical radiotherapy.