Loebner Hannes A, Bertholet Jenny, Mackeprang Paul-Henry, Volken Werner, Elicin Olgun, Mueller Silvan, Guyer Gian, Aebersold Daniel M, Stampanoni Marco F M, Fix Michael K, Manser Peter
Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern, Bern, Switzerland.
Institute for Biomedical Engineering, ETH Zürich and PSI, Villigen, Switzerland.
Phys Imaging Radiat Oncol. 2024 May 10;30:100586. doi: 10.1016/j.phro.2024.100586. eCollection 2024 Apr.
Dynamic trajectory radiotherapy (DTRT) has been shown to improve healthy tissue sparing compared to volumetric arc therapy (VMAT). This study aimed to assess and compare the robustness of DTRT and VMAT treatment-plans for head and neck (H&N) cancer to patient-setup (PS) and machine-positioning uncertainties.
The robustness of DTRT and VMAT plans previously created for 46 H&N cases, prescribed 50-70 Gy to 95 % of the planning-target-volume, was assessed. For this purpose, dose distributions were recalculated using Monte Carlo, including uncertainties in PS (translation and rotation) and machine-positioning (gantry-, table-, collimator-rotation and multi-leaf collimator (MLC)). Plan robustness was evaluated by the uncertainties' impact on normal tissue complication probabilities (NTCP) for xerostomia and dysphagia and on dose-volume endpoints. Differences between DTRT and VMAT plan robustness were compared using Wilcoxon matched-pair signed-rank test ( = 5 %).
Average NTCP for moderate-to-severe xerostomia and grade ≥ II dysphagia was lower for DTRT than VMAT in the nominal scenario (0.5 %, p = 0.01; 2.1 %, p < 0.01) and for all investigated uncertainties, except MLC positioning, where the difference was not significant. Average differences compared to the nominal scenario were 3.5 Gy for rotational PS ( 3°) and machine-positioning ( 2°) uncertainties, <7 Gy for translational PS uncertainties ( 5 mm) and < 20 Gy for MLC-positioning uncertainties ( 5 mm).
DTRT and VMAT plan robustness to the investigated uncertainties depended on uncertainty direction and location of the structure-of-interest to the target. NTCP remained on average lower for DTRT than VMAT even when considering uncertainties.
与容积弧形调强放疗（VMAT）相比，动态轨迹放疗（DTRT）已被证明可改善对健康组织的保护。本研究旨在评估和比较DTRT与VMAT对头颈部（H&N）癌的治疗计划对患者摆位（PS）和机器定位不确定性的稳健性。
评估了先前为46例H&N病例制定的DTRT和VMAT计划的稳健性，计划靶体积的95%处方剂量为50 - 70 Gy。为此，使用蒙特卡罗方法重新计算剂量分布，包括PS（平移和旋转）和机器定位（机架、治疗床、准直器旋转和多叶准直器（MLC））的不确定性。通过不确定性对口干和吞咽困难的正常组织并发症概率（NTCP）以及剂量体积终点的影响来评估计划的稳健性。使用Wilcoxon配对符号秩检验比较DTRT和VMAT计划稳健性的差异（α = 5%）。
在标称情况下，DTRT的中度至重度口干和≥II级吞咽困难的平均NTCP低于VMAT（0.5%，p = 0.01；2.1%，p < 0.01），并且在所有研究的不确定性情况下均如此，但MLC定位除外，其差异不显著。与标称情况相比，旋转PS（±3°）和机器定位（±2°）不确定性的平均差异为3.5 Gy，平移PS不确定性（±5 mm）<7 Gy，MLC定位不确定性（±5 mm）<20 Gy。
DTRT和VMAT计划对所研究不确定性的稳健性取决于不确定性方向以及感兴趣结构相对于靶区的位置。即使考虑不确定性，DTRT的NTCP平均仍低于VMAT。
