Linear-quadratic analysis of tumour response to fractionated radiotherapy: a study on human squamous cell carcinoma xenografts

Purpose: To compare values for the alpha / beta ratio in experimental tumours irradiated either under conditions of clamping and short overall time or under more 'clinically realistic' conditions. Materials and methods: Human squamous cell carcinomas, FaDu and GL, were grown in nude mice....

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Bibliographic Details
Published in:International journal of radiation biology 1998, Vol.73 (2), p.197-205
Main Authors: PETERSEN, C, BAUMANN, M, DUBBEN, H.-H, ARPS, H, MELENKEIT, A, HELFRICH, J
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Carcinoma, Squamous Cell - radiotherapy
Dose-Response Relationship, Radiation
Female
Head and Neck Neoplasms - radiotherapy
Humans
Male
Medical sciences
Mice
Mice, Nude
Radiation therapy and radiosensitizing agent
Radiotherapy Dosage
Transplantation, Heterologous
Treatment with physical agents
Treatment. General aspects
Tumor Cells, Cultured
Tumors
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Summary:Purpose: To compare values for the alpha / beta ratio in experimental tumours irradiated either under conditions of clamping and short overall time or under more 'clinically realistic' conditions. Materials and methods: Human squamous cell carcinomas, FaDu and GL, were grown in nude mice. alpha / beta values were determined from local tumour control data after treatment with single doses and 2, 4, and 8 fractions under clamp hypoxia in 3.5 days, using maximum likelihood analysis. Effective alpha / beta values (alpha / beta) were determined from treatment with 12, 30, and 60 fractions under ambient conditions in a constant overall treatment time of 6 weeks. Results: After correction for an oxygen 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 TCD values after 12 to 60 50 fractions were not significantly different, the alpha / beta value was eff infinite (52; inf.). Unexpected from the high alpha / beta value, the TCD values of GL tumours increased from 37 Gy (28; 47) after 50 12 fractions to 59 Gy (52; 67) after 60 fractions: the alpha / beta value eff 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 impact on treatment outcome when the number of fractions is changed in clinical radiotherapy. eff
ISSN:0955-3002
1362-3095
DOI:10.1080/095530098142581