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Impact of variable RBE on proton fractionation.
MedLine Citation:
PMID:  23298075     Owner:  NLM     Status:  In-Data-Review    
Purpose: To explore the impact of variable proton relative biological effectiveness (RBE) on dose fractionation for clinically relevant situations. A generic RBE = 1.1 is generally used for isoeffect calculations, while experimental studies showed that proton RBE varies with tissue type, dose, and linear energy transfer (LET).Methods: An analytical expression for the LET and α∕β dependence of the linear-quadratic (LQ) model has been used for proton simulations in parallel with the assumption of a generic RBE = 1.1. Calculations have been performed for ranges of LET values and fractionation sensitivities to describe clinically relevant cases, such as the treatment of head and neck and prostate tumors. Isoeffect calculations were compared with predictions from a generic RBE value and reported clinical results.Results: The generic RBE = 1.1 appears to be a reasonable estimate for the proton RBE of rapidly growing tissues irradiated with low LET radiation. However, the use of a variable RBE predicts larger differences for tissues with low α∕β (both tumor and normal) and at low doses per fraction. In some situations these differences may appear in contrast to the findings from photon studies highlighting the importance of accurate accounting for the radiobiological effectiveness of protons. Furthermore, the use of variable RBE leads to closer predictions to clinical results.Conclusions: The LET dependence of the RBE has a strong impact on the predicted effectiveness of fractionated proton radiotherapy. The magnitude of the effect is modulated by the fractionation sensitivity and the fractional dose indicating the need for accurate analyses both in the target and around it. Care should therefore be employed for changing clinical fractionation patterns or when analyzing results from clinical studies for this type of radiation.
Alexandru Dasu; Iuliana Toma-Dasu
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Medical physics     Volume:  40     ISSN:  0094-2405     ISO Abbreviation:  Med Phys     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-01-09     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0425746     Medline TA:  Med Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  011705     Citation Subset:  IM    
Department of Radiation Physics UHL, County Council of Östergötland, 581 85 Linköping, Sweden and Radiation Physics, Department of Medical and Health Sciences, Faculty of Health Sciences, Linköping University, 581 83 Linköping, Sweden.
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