Murr Martina, Wegener Daniel, Böke Simon, Gani Cihan, Mönnich David, Niyazi Maximilian, Schneider Moritz, Zips Daniel, Müller Arndt-Christian, Thorwarth Daniela
Section for Biomedical Physics, Department of Radiation Oncology, University of Tübingen, Germany.
Department of Radiation Oncology, University Hospital Tübingen, Tübingen, Germany.
Phys Imaging Radiat Oncol. 2024 Oct 28;32:100662. doi: 10.1016/j.phro.2024.100662. eCollection 2024 Oct.
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).
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.
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.
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.
传统图像引导放射治疗（conv-IGRT）是前列腺癌（PC）的标准治疗方法，但未考虑分次治疗间的解剖结构变化。在线自适应磁共振引导放射治疗（OA-MRgRT）可能会改善危及器官（OARs）的保护和临床靶区（CTV）的覆盖。本研究的目的是分析与治疗前参考计划（refPlan）相比，OA-MRgRT和conv-IGRT治疗PC后累积的OAR和靶区剂量。
纳入10例先前在1.5T MR直线加速器上接受OA-MRgRT治疗（20次，每次3Gy）的PC患者。通过对所有分次的MR图像进行变形配准来确定累积的OA-MRgRT剂量。通过将计划计算机断层扫描与每个分次的MR图像进行刚性配准来模拟conv-IGRT，以进行剂量映射/累积。使用Wilcoxon符号秩检验比较剂量体积参数（DVPs），包括OA-MRgRT、conv-IGRT和refPlan的CTV D50%和D98%、直肠、膀胱、尿道的Dmax以及V56Gy。使用正常组织并发症概率模型分析累积剂量差异的临床相关性。
CTV-DVPs具有可比性，而与conv-IGRT相比，OA-MRgRT产生的OAR-DVPs中位数降低，但膀胱V56Gy除外。与conv-IGRT（59.1/59.9Gy，p = 0.006）和refPlan（60.1Gy，p = 0.012）相比，OA-MRgRT显示直肠Dmax中位数显著更低。同样，与conv-IGRT（60.0/60.4Gy，p = 0.006）和refPlan（61.2Gy，p = 0.002）相比，OA-MRgRT产生的膀胱Dmax中位数降低。总体而言，累积剂量差异较小，未转化为临床相关效应。
在PC中使用20次，每次3Gy进行变形累积的OA-MRgRT与conv-IGRT相比显示出显著但较小的剂量学差异。证明了一种剂量累积方法的可行性，这可能与评估未来的低分割OA-MRgRT方法相关。
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