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Relative clinical effectiveness of carbon ion radiotherapy: theoretical modelling for H&N tumours
Stockholm University, Faculty of Science, Department of Physics.
Linköping University, Sweden.ORCID iD: 0000-0001-8171-2541
National Institute of Radiological Sciences, Japan.ORCID iD: 0000-0003-4213-7331
Stockholm University, Faculty of Science, Department of Physics. Karolinska Institutet, Sweden.ORCID iD: 0000-0002-7101-240X
2015 (English)In: Journal of radiation research, ISSN 0449-3060, E-ISSN 1349-9157, Vol. 56, no 4, 639-645 p.Article in journal (Refereed) Published
Abstract [en]

Comparison of the efficiency of photon and carbon ion radiotherapy (RT) administered with the same number of fractions might be of limited clinical interest, since a wide range of fractionation patterns are used clinically today. Due to advanced photon treatment techniques, hypofractionation is becoming increasingly accepted for prostate and lung tumours, whereas patients with head and neck tumours still benefit from hyperfractionated treatments. In general, the number of fractions is considerably lower in carbon ion RT. A clinically relevant comparison would be between fractionation schedules that are optimal within each treatment modality category. In this in silico study, the relative clinical effectiveness (RCE) of carbon ions was investigated for human salivary gland tumours, assuming various radiation sensitivities related to their oxygenation. The results indicate that, for hypoxic tumours in the absence of reoxygenation, the RCE (defined as the ratio of D50 for photons to carbon ions) ranges from 3.5 to 5.7, corresponding to carbon ion treatments given in 36 and 3 fractions, respectively, and 30 fractions for photons. Assuming that interfraction local oxygenation changes take place, results for RCE are lower than that for an oxic tumour if only a few fractions of carbon ions are used. If the carbon ion treatment is given in more than 12 fractions, the RCE is larger for the hypoxic than for the well-oxygenated tumour. In conclusion, this study showed that in silico modelling enables the study of a wide range of factors in the clinical considerations and could be an important step towards individualisation of RT treatments.

Place, publisher, year, edition, pages
2015. Vol. 56, no 4, 639-645 p.
Keyword [en]
hypoxia, RBE, TCP, carbon ion, fractionation, RCE
National Category
Physical Sciences
URN: urn:nbn:se:su:diva-102720DOI: 10.1093/jrr/rrv016ISI: 000360990700005OAI: diva2:712888
Available from: 2014-04-16 Created: 2014-04-16 Last updated: 2015-11-04Bibliographically approved
In thesis
1. Radiobiological end-points for the theoretical evaluation of the effectiveness of carbon ions and photons in treating tumours with dynamic hypoxia
Open this publication in new window or tab >>Radiobiological end-points for the theoretical evaluation of the effectiveness of carbon ions and photons in treating tumours with dynamic hypoxia
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Tumours are characterised by unorganised vasculature, which often results in hypoxic regions. Hypoxia is a common cause for photon radiotherapy (RT) treatment failure, as hypoxic cells require up to 2-3 times higher doses compared to well-oxygenated cells for the same effect in terms of cell kill. The increase in dose that would be required to treat the tumours of cancer patients is limited by the radiation sensitivity of surrounding normal tissues. Using carbon ions instead of photons, the radiation dose can be conformed to the tumour to a much higher degree, resulting in an improved sparing of normal tissues. In addition, carbon ions have a much higher radiobiological effectiveness near the end of their range, which is positioned in the tumour. Also, the radiation modes of action leading to cell death when carbon ions interact with living tissues, are less sensitive to the oxygen status compared with the action modes of photons.

The focus of this thesis lies in the development of models for the computation of the cell surviving fraction and tumour control probability (TCP) in hypoxic tumours after photon and carbon ion RT. The impact of fractionation was evaluated with regard to possible spatial changes in oxygenation, both for stereotactic body RT and for carbon ion RT. The feasibility of a method to determine and deliver the optimal photon dose for achieving a high TCP according to spatial variations in radiation sensitivity was evaluated in a treatment planning study. The radiobiological models were finally used for the theoretical quantification of the gain in using carbon ions instead of photons.

The results show that there are great possibilities to increase the number of positive outcomes of radiation treatment of tumours if the key influential factors are taken into account, such as level and distribution of hypoxia, radiation quality and choice of fractionation schedule.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2014. 50 p.
OER, hypoxia, LOC, RCR, hypofractionation, SBRT, carbon ion, fractionation, TCP, SF, RCE, RBE
National Category
Other Physics Topics
Research subject
Medical Radiation Physics
urn:nbn:se:su:diva-102731 (URN)978-91-7447-835-8 (ISBN)
Public defence
2014-05-27, CCK Lecture Hall, R8:00, Karolinska Sjukhuset, Solna, 13:00 (English)

At the time of the doctoral defence the following papers were unpublished and had a status as follows; Paper 3: Manuscript; Paper 4: Epubl ahead of print; Paper 5: Manuscript

Available from: 2014-05-05 Created: 2014-04-17 Last updated: 2014-05-05Bibliographically approved

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