Regnery Sebastian, Katsigiannopulos Efthimios, Lau Hin, Hoegen-Saßmannshausen Philipp, Weykamp Fabian, Renkamp Claudia Katharina, Rippke Carolin, Schlüter Fabian, Albert Sophia, Meis Jan, Kirchner Marietta, Balzer Alexandra, Andratschke Nicolaus, Guckenberger Matthias, Debus Jürgen, Klüter Sebastian, Hörner-Rieber Juliane
Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.
NCT Partner Site Heidelberg, A Clinical-Translational Cancer Research Partnership between University Hospital Heidelberg and DKFZ, Germany.
Clin Transl Radiat Oncol. 2024 Dec 7;51:100899. doi: 10.1016/j.ctro.2024.100899. eCollection 2025 Mar.
To use imaging data from stereotactic MR-guided online adaptive radiotherapy (SMART) of ultracentral lung tumors (ULT) for development of a safe non-adaptive approach towards stereotactic body radiotherapy (SBRT) of ULT.
Analysis is based on 19 patients with ULT who received SMART (10 × 5.0-5.5 Gy) on a 0.35 T MR-Linac (MRIdian®) in the prospective MAGELLAN trial. 4D-planning CT data of six patients served to quantify proximal bronchial tree (PBT) breathing motion. Daily fraction MRIs are used to calculate interfractional translations (mediolateral (ML), anterior-posterior (AP), superior-inferior (SI)) and their dosimetric consequences for the PBT. A planning risk volume (PRV) is calculated for an assumed non-adaptive SBRT in deep-inspiration breath hold (DIBH) with surface-guidance (AlignRT®). Finally, non-adaptive volumetric modulated arc (VMAT) SBRT is simulated with and without a PRV for N = 10 patients (10 × 5.5 Gy).
The PBT shows relevant breathing motion, especially in superior-inferior direction (median ML: 2.5 mm, AP: 1.9 mm and SI: 9.2 mm). Furthermore, moderate interfractional translations are observed (mean absolute translation ML: 1.3 mm, AP: 1.3 mm, SI: 1.1 mm), with an estimated 2 mm PRV margin for interfractional changes alone. Simulated non-adaptive SBRT leads to PBT overdoses in 60 % of patients (median overdosed fractions VMAT: 2.5, predicted MR-linac plans 4). Both MR-guided online plan adaptation (SMART) and PRV-based non-adaptive VMAT prevent PBT overdoses, but SMART yields significantly higher planning target volume (PTV) coverage (SMART: median 96 % [IQR 95-96], VMAT: median 89 % [IQR 77-94], p = 0.014).
Both intrafractional breathing motion and interfractional translations may impact doses to the PBT during SBRT of ULT. SMART protects the PBT from overdoses while maintaining high PTV coverage. Non-adaptive SBRT appears safe with advanced breathing motion management and PRV, but yields inferior PTV coverage.
利用超中央型肺癌（ULT）立体定向磁共振引导在线自适应放疗（SMART）的影像数据，开发一种针对ULT立体定向体部放疗（SBRT）的安全非自适应方法。
分析基于19例接受前瞻性麦哲伦试验中0.35T MR直线加速器（MRIdian®）上SMART（10×5.0 - 5.5Gy）治疗的ULT患者。6例患者的4D计划CT数据用于量化近端支气管树（PBT）的呼吸运动。每日分次MRI用于计算分次间平移（内外侧（ML）、前后（AP）、上下（SI））及其对PBT的剂量学影响。计算在深吸气屏气（DIBH）下采用表面引导（AlignRT®）的假定非自适应SBRT的计划风险体积（PRV）。最后，对N = 10例患者（10×5.5Gy）模拟有无PRV的非自适应容积调强弧形放疗（VMAT）SBRT。
PBT显示出明显的呼吸运动，尤其是在上下方向（ML中位数：2.5mm，AP：1.9mm，SI：9.2mm）。此外，观察到适度的分次间平移（平均绝对平移ML：1.3mm，AP：1.3mm，SI：1.1mm），仅分次间变化估计PRV边界为2mm。模拟的非自适应SBRT导致60%的患者PBT过量（VMAT过量分次中位数：2.5，预测的MR直线加速器计划为4次）。磁共振引导的在线计划自适应（SMART）和基于PRV的非自适应VMAT均可防止PBT过量，但SMART产生的计划靶体积（PTV）覆盖率显著更高（SMART：中位数96%[四分位间距95 - 96]，VMAT：中位数89%[四分位间距77 - 94]，p = 0.014）。
在ULT的SBRT期间，分次内呼吸运动和分次间平移均可能影响PBT的剂量。SMART可保护PBT不发生过量，同时保持高PTV覆盖率。采用先进的呼吸运动管理和PRV，非自适应SBRT似乎是安全的，但PTV覆盖率较低。
