Comparison of online adaptive and non-adaptive magnetic resonance image-guided radiation therapy in prostate cancer using dose accumulation

Martina Murr; Daniel Wegener; Simon Böke; Cihan Gani; David Mönnich; Maximilian Niyazi; Moritz Schneider; Daniel Zips; Arndt-Christian Müller; Daniela Thorwarth

doi:10.1016/j.phro.2024.100662

Comparison of online adaptive and non-adaptive magnetic resonance image-guided radiation therapy in prostate cancer using dose accumulation

Phys Imaging Radiat Oncol. 2024 Oct 28:32:100662. doi: 10.1016/j.phro.2024.100662. eCollection 2024 Oct.

Authors

Martina Murr¹, Daniel Wegener^{2

3}, Simon Böke², Cihan Gani², David Mönnich¹, Maximilian Niyazi², Moritz Schneider¹, Daniel Zips^{2

4

5}, Arndt-Christian Müller^{2

6}, Daniela Thorwarth¹

Affiliations

¹ Section for Biomedical Physics, Department of Radiation Oncology, University of Tübingen, Germany.
² Department of Radiation Oncology, University Hospital Tübingen, Tübingen, Germany.
³ Department of Radiation Oncology, Alb-Fils Kliniken GmbH, Goeppingen, Germany.
⁴ Department of Radiation Oncology, Berlin Institute of Health, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin, Germany.
⁵ German Cancer Consortium (DKTK), partner site Tübingen, and German Cancer Research Center (DKFZ), Heidelberg, Germany.
⁶ Department of Radiation Oncology and Radiotherapy, RKH-Kliniken Ludwigsburg, Ludwigsburg, Germany.

Abstract

Background and purpose: Conventional image-guided radiotherapy (conv-IGRT) is standard in prostate cancer (PC) but does not account for inter-fraction anatomical changes. Online-adaptive magnetic resonance-guided RT (OA-MRgRT) may improve organ-at-risk (OARs) sparing and clinical target volume (CTV) coverage. The aim of this study was to analyze accumulated OAR and target doses in PC after OA-MRgRT and conv-IGRT in comparison to pre-treatment reference planning (refPlan).

Material and methods: Ten patients with PC, previously treated with OA-MRgRT at the 1.5 T MR-Linac (20x3Gy), were included. Accumulated OA-MRgRT doses were determined by deformably registering all fraction's MR-images. Conv-IGRT was simulated through rigid registration of the planning computed tomography with each fraction's MR-image for dose mapping/accumulation. Dose-volume parameters (DVPs), including CTV D50% and D98%, rectum, bladder, urethra, Dmax and V56Gy for OA-MRgRT, conv-IGRT and refPlan were compared using the Wilcoxon signed-rank test. Clinical relevance of accumulated dose differences was analyzed using a normal-tissue complication-probability model.

Results: CTV-DVPs were comparable, whereas OA-MRgRT yielded decreased median OAR-DVPs compared to conv-IGRT, except for bladder V56Gy. OA-MRgRT demonstrated significantly lower median rectum Dmax over conv-IGRT (59.1/59.9 Gy, p = 0.006) and refPlan (60.1 Gy, p = 0.012). Similarly, OA-MRgRT yielded reduced median bladder Dmax compared to conv-IGRT (60.0/60.4 Gy, p = 0.006), and refPlan (61.2 Gy, p = 0.002). Overall, accumulated dose differences were small and did not translate into clinically relevant effects.

Conclusion: Deformably accumulated OA-MRgRT using 20x3Gy in PC showed significant but small dosimetric differences comparted to conv-IGRT. Feasibility of a dose accumulation methodology was demonstrated, which may be relevant for evaluating future hypo-fractionated OA-MRgRT approaches.

Keywords: Deformable image registration; Dose accumulation; MR-Linac; MR-guided Radiotherapy; Prostate Cancer.