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The impact of hypoxia on tumour control probability in the high-dose range used in stereotactic body radiation therapy
Stockholm University, Faculty of Science, Medical Radiation Physics (together with KI).
2012 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The use of stereotactic body radiation therapy employing few large fractions of radiation dose for the treatment of non-small cell lung cancer has been proven very successful, high values of tumour control probability (TCP) being clinically achieved. In spite of the success of the fractionation schedules currently used, there is a tendency towards reducing the number of fractions for economical and practical reasons, and also for maximizing the comfort of the patients. It is therefore the main aim of this thesis to investigate the impact of a severely reduced number of fractions on the tumour control probability for tumours that contain hypoxic areas. The impact on TCP of other factors such as hypoxic fraction, distribution of the oxygen partial pressure and location of the hypoxic volume within the tumour were also investigated. The effect of tumour motion due to breathing was included and evaluated using Cone Beam Computed Tomography (CBCT) data from patients imaged with internal markers in the liver and pancreas. The results clearly showed that in the presence of hypoxia, TCP is seriously compromised if there is not enough time for reoxygenation between fractions. A reduction in the number of fractions of just one fraction may require an increase of several Gy per fraction to obtain a similar TCP. The diaphragmatic tumour motion range showed little influence on TCP provided that the PTV encompassed all tumour positions. The dose delivered to the PTV margin was found not to be the only factor that is significant for local control, the average dose correlated better with TCP. The agreement of the results of this work with clinical results also serve as a strong indicator that inter-fraction reoxygenation is an important process in real-life patients treated with stereotactic body radiotherapy.

Place, publisher, year, edition, pages
2012. , 67 p.
Keyword [en]
Radiobiological modeling, Hypoxia, Stereotactic body radiotherapy, Hypofractionation, SBRT, Non-small cell lung cancer, NSCLC
National Category
Natural Sciences Physical Sciences
URN: urn:nbn:se:su:diva-84518OAI: diva2:580722
2012-06-18, 21:22 (English)
Physics, Chemistry, Mathematics
Available from: 2013-01-28 Created: 2012-12-25 Last updated: 2013-01-28Bibliographically approved

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