LINEAR-QUADRATIC ANALYSIS OF TUMOR RESPONSE TO FRACTIONATED RADIOTHERAPY - A STUDY ON HUMAN SQUAMOUS-CELL CARCINOMA XENOGRAFTS

Citation
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
ISSN journal
0955-3002
Volume
73
Issue
2
Year of publication
1998
Pages
197 - 205
Database
ISI
SICI code
0955-3002(1998)73:2<197:LAOTRT>2.0.ZU;2-G
Abstract
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.