ESTRO38 Congress Report

2. JACK FOWLER UNIVERSITY OF WISCONSIN AWARD

First clinical real-time motion-including tumour dose reconstruction during radiotherapy delivery (E38-1431) S. Skouboe, T. Ravkilde, J. Bertholet, R. Hansen, E. Worm, C. G. Muurholm, B. Weber, M. Høyer, P.R. Poulsen

Aarhus University Hospital, Denmark

Context of the study Due to respiration, a tumour may move during radiotherapy treatment, which can compromise the tumour dose. My research focuses on calculating the actually delivered dose during treatment delivery while taking tumour motion into account. Overview of abstract Organs and tumours may move during radiotherapy treatment for cancer, e.g. due to respiration. This can compromise tumour dose coverage and may reduce the local control probability, in particular for stereotactic body radiotherapy where high doses are delivered in few fractions. My research focuses on calculating the actual delivered dose during treatment delivery while taking tumour motion into account. Using our in-house developed software program, DoseTracker, we successfully managed to monitor the tumour dose in ongoing treatments of liver cancer. This research can be used for quality assurance or dose-guided decision-making. What were the three main findings of your research? 1. We can calculate the actually delivered tumour dose in the patient in real-time during treatment while taking tumour motion into account. 2. We canmonitor the instantaneous as well as cumulative dose for individual points and the dose distribution for the tumour as a whole. 3. The dose results were benchmarked against a more accurate algorithm, which cannot be applied in real-time during treatment. Our real-time calculated dose errors matched these calculations well. What impact could your research have? Tumours may move during treatment due to respiration, but the dosimetric impact of the motion is often not well known. The motion may compromise tumour and organ at risk doses, and uncertainties in the actual delivered dose complicates the interpretation of dose-response relationships in radiotherapy. The dose reconstruction of DoseTracker gives a more exact knowledge of the actual delivered dose. Since the dose information is available in real time it provides on-the-fly quality assurance (QA) of the treatment being delivered. This could in particular be beneficial for advanced treatments such as MLC tracking, where treatment plan adaptations during treatment delivery is a challenge for conventional pre-treatment QAmethods.

Is this research indicative of a bigger trend in oncology? There is currently a growing interest in motion monitoring during radiotherapy delivery and real-time treatment adaptation to themotion by methods such as MLC tracking. This interest will likely increase further with the clinical introduction of the MR-linac. Our research aligns well with this trend by combining real-time motion monitoring with real-time tumour dose reconstruction during clinical SBRT delivery on a standard linear accelerator. The real-time reconstructed dose may open new possibilities for real- time adaptation based on doses rather than geometry.

AWARDS | Congress report

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