Tison Thaïs, Dechambre David, Pierrard Julien, Everard Louise, Geets Xavier
Radiation Oncology, Cliniques Universitaires Saint-Luc, Brussels, BEL.
Medical Physics, Cliniques Universitaires Saint-Luc, Brussels, BEL.
Cureus. 2024 Sep 8;16(9):e68919. doi: 10.7759/cureus.68919. eCollection 2024 Sep.
Online adaptive radiotherapy (oART) uses daily imaging to identify changes in the patient's anatomy and generate a new treatment plan adapted to these changes, and it can be used for treating gastric mucosa-associated lymphoid tissue (MALT) lymphomas. This study aimed to determine the intrafraction motion and planning target volume (PTV) margins required for an oART workflow on a cone beam computed tomography (CBCT)-based dedicated system (Ethos®, Varian Medical Systems, Palo Alto, California, United States) and investigate the potential benefits for patients compared with a non-adaptive workflow. Involving three patients treated for gastric MALT lymphoma with the oART under breath-hold (BH) technique, the study determined a PTV margin for adaptive treatment using CBCT scans performed at the beginning and just before treating the patients for 34 fractions. Different PTVs were made by isotropically extending the clinical target volume (CTV) contoured on the first CBCT (CTV1) at intervals of 1 mm to evaluate intrafraction gastric motion, with the expansion covering the contoured CTV on the second CBCT (CTV2) quantifying the intrafraction motion (adaptive treatment) and the expansion from the CTV delineated on the planning scanner (CTVplanning) that could cover both CTV1 and CTV2 defining the interfraction motion (non-adaptive treatment). PTV margins were then determined as the extension of the CTV allowing coverage of 95% of its volume in 90% of fractions, and the dosimetric impact on dose constraints between an adaptive plan and a non-adaptive plan based on the predetermined margins was evaluated. A total of 68 CBCTs were analyzed, revealing that the PTV margin for oART was 4 mm, while for non-adaptive treatment it was 12 mm, with an average time elapsed between CBCT1 and CBCT2 of 11.62 minutes and no correlation between inter-CBCT timing and PTV margins (Pearson R-coefficient=0.10). All dosimetric constraints were met in both adaptive and non-adaptive plans, but the adaptive plan allowed for reduced organ-at-risk (OAR) doses in each patient. The study concluded that oART could reduce PTV margins in the treatment of gastric MALT lymphoma, especially with a BH strategy, impacting OAR dosimetry, though more prospective studies are required to validate these findings and determine their clinical impact on patients.
在线自适应放疗（oART）利用每日成像来识别患者解剖结构的变化，并生成适应这些变化的新治疗计划，它可用于治疗胃黏膜相关淋巴组织（MALT）淋巴瘤。本研究旨在确定基于锥形束计算机断层扫描（CBCT）的专用系统（Ethos®，瓦里安医疗系统公司，美国加利福尼亚州帕洛阿尔托）上oART工作流程所需的分次内运动和计划靶区（PTV）边界，并研究与非自适应工作流程相比对患者的潜在益处。该研究纳入了3例采用oART屏气（BH）技术治疗胃MALT淋巴瘤的患者，通过在开始治疗前及治疗34次时对患者进行CBCT扫描，确定自适应治疗的PTV边界。通过以1mm间隔各向同性扩展在首次CBCT上勾画的临床靶区（CTV）（CTV1）来制作不同的PTV，以评估分次内胃部运动，扩展范围覆盖第二次CBCT上勾画的CTV（CTV2）以量化分次内运动（自适应治疗），以及从计划扫描器上勾画的CTV（CTVplanning）扩展以覆盖CTV1和CTV2来定义分次间运动（非自适应治疗）。然后将PTV边界确定为CTV的扩展，以允许在90%的分次中覆盖其95%的体积，并评估基于预定边界的自适应计划和非自适应计划之间对剂量限制的剂量学影响。共分析了68次CBCT，结果显示oART的PTV边界为4mm，而非自适应治疗为12mm，CBCT1和CBCT2之间的平均时间间隔为11.62分钟，且CBCT间时间与PTV边界之间无相关性（Pearson R系数=0.10）。自适应计划和非自适应计划均满足所有剂量学限制，但自适应计划可降低每位患者的危及器官（OAR）剂量。该研究得出结论，oART可降低胃MALT淋巴瘤治疗中的PTV边界，尤其是采用BH策略时，对OAR剂量学有影响，不过需要更多前瞻性研究来验证这些发现并确定其对患者的临床影响。
