University of Groningen, University Medical Centre Groningen, Department of Radiation Oncology, The Netherlands.
University of Groningen, University Medical Centre Groningen, Department of Radiation Oncology, The Netherlands.
Radiother Oncol. 2022 Mar;168:221-228. doi: 10.1016/j.radonc.2022.01.043. Epub 2022 Feb 5.
To evaluate the dosimetric changes occurring over the treatment course for nasopharyngeal carcinoma (NPC) patients treated with robustly optimised intensity modulated proton therapy (IMPT).
25 NPC patients were treated to two dose levels (CTV1: 70 Gy, CTV2: 54.25 Gy) with robustly optimised IMPT plans. Robustness evaluation was performed over 28 error scenarios using voxel-wise minimum distributions to assess target coverage and voxel-wise maximum distributions to assess possible hotspots and critical organ doses. Daily CBCT was used for positioning and weekly repeat CTs (rCT) were taken, on which the plan dose was recalculated and robustly evaluated. Deformable image registration was used to warp and accumulate the nominal, voxel-wise minimum and maximum rCT dose distributions. Changes to target coverage, critical organ and normal tissue dose between the accumulated and planned doses were investigated.
2 patients required a plan adaptation due to reduced target coverage. The D98% in the accumulated voxel-wise minimum distribution was higher than planned for CTV1 in 24/25 patients and for CTV2 in 20/25 patients. Maximum doses to the critical organs remained acceptable in all patients. Other normal tissue doses showed some variation as a result of soft tissue deformations and weight change. Normal tissue complication probabilities for grade ≥ 2 dysphagia and grade ≥ 2 xerostomia remained similar to planned values.
Robustly optimised IMPT plans, in combination with volumetric verification imaging and adaptive planning, provided robust target coverage and acceptable OAR dose variation in our NPC cohort when accumulated over longitudinal data.
评估接受优化强度调制质子治疗（IMPT）的鼻咽癌（NPC）患者在治疗过程中剂量变化。
25 名 NPC 患者接受了两种剂量水平（CTV1：70Gy，CTV2：54.25Gy）的优化 IMPT 计划治疗。使用体素最小分布进行稳健性评估，评估 28 种误差情况，以评估靶区覆盖，使用体素最大分布评估可能的热点和关键器官剂量。每天进行锥形束 CT（CBCT）定位，每周进行重复 CT（rCT）扫描，在 rCT 上重新计算和稳健评估计划剂量。使用变形图像配准对名义、体素最小和最大 rCT 剂量分布进行配准和累积。研究了目标覆盖、关键器官和正常组织剂量在累积剂量和计划剂量之间的变化。
由于靶区覆盖减少，2 名患者需要进行计划调整。25 名患者中有 24 名，CTV1 累积体素最小分布的 D98%高于计划值，25 名患者中有 20 名，CTV2 累积体素最小分布的 D98%高于计划值。所有患者的关键器官最大剂量仍可接受。由于软组织变形和体重变化，其他正常组织剂量也有一些变化。2 级以上吞咽困难和 2 级以上口干的正常组织并发症概率与计划值相似。
在我们的 NPC 队列中，结合容积验证成像和自适应计划，使用稳健优化的 IMPT 计划，在纵向数据上累积时，为靶区提供了稳健的覆盖，关键器官剂量变化可接受。
