Impact of variable RBE on proton fractionation
2013 (English)In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 40, no 1, 011705Article in journal (Refereed) Published
Purpose: To explore the impact of variable proton 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 LET.
Material and methods: An analytical expression for the LET and α/β dependence of the 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, like the treatment of H&N 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.
Place, publisher, year, edition, pages
2013. Vol. 40, no 1, 011705
proton radiotherapy, fractionation, LQ model, RBE
Cancer and Oncology
Research subject Medical Radiation Physics; Radiation Physics; Oncology
IdentifiersURN: urn:nbn:se:su:diva-82183DOI: 10.1118/1.4769417ISI: 000313033200009OAI: oai:DiVA.org:su-82183DiVA: diva2:566865