Lavan N A, Smyth G, McQuaid D, Gaze M N, Stacey C, Vaidya S, Saran F H, Oelfke U, Mandeville H C
Department of Radiotherapy, The Royal Marsden NHS Foundation Trust and the Institute of Cancer Research, Sutton, UK.
Joint Department of Physics at the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, Sutton, UK.
Clin Oncol (R Coll Radiol). 2024 Dec;36(12):780-789. doi: 10.1016/j.clon.2024.08.009. Epub 2024 Aug 14.
The magnitude of upper abdominal organ motion in children may be overestimated by current planning target volumes (PTV). A four-dimensional computed tomography (4DCT) - derived internal target volume (ITV) is frequently used in adult radiotherapy to take respiratory-related organ motion into account. In this study, the dosimetric consequences for target coverage and organs at risk from the use of an ITV approach compared to standard PTV margins in children with high-risk neuroblastoma were investigated.
14 patients, median age 4.1 years, range 1.5 - 18.9 years, (9 midline targets, 5 lateralised) each had two dual arc volumetric modulated arc therapy (VMAT) plans (14 ×1.5 Gy) generated. One used an ITV-approach; motion information derived from 4DCT (PTV_itv) with a 5mm ITV to PTV expansion, and the other a PTV margin of 10mm from CTV to PTV (PTV_standard). Differences in absolute PTV volume and organ at risk doses are described.
The ITV approach resulted in a highly significant reduction in PTV size of 38% (p<0.0001). For midline targets, an ITV approach resulted in a small but statistically significant reduction in combined mean kidney dose of 0.8Gy, p 0.01. Mean heart and lung dose were reduced by an average of 1 Gy with an ITV approach. Non-PTV integral dose from 30.4 Gy L to 27.8 Gy L using an ITV approach.
An ITV-approach to respiratory related organ motion management in children can significantly reduce absolute PTV volumes, maintain target coverage and reduce dose delivered to normal tissue in proximity to the target. This is an essential step to maximising the benefits of highly conformal radiotherapy techniques including VMAT for this patient group, and in the future with Proton Therapy.
当前的计划靶区（PTV）可能高估了儿童上腹部器官的运动幅度。在成人放射治疗中，常使用基于四维计算机断层扫描（4DCT）得出的内部靶区（ITV）来考虑与呼吸相关的器官运动。本研究调查了在高危神经母细胞瘤患儿中，与标准PTV边界相比，使用ITV方法对靶区覆盖和危及器官剂量的剂量学影响。
14例患者，中位年龄4.1岁，年龄范围1.5 - 18.9岁，（9个中线靶区，5个侧方靶区），每个患者均生成了两个双弧容积调强弧形放疗（VMAT）计划（14×1.5 Gy）。一个计划采用ITV方法；从4DCT获取运动信息（PTV_itv），ITV到PTV扩展5mm，另一个计划从临床靶区（CTV）到PTV的边界为10mm（PTV_标准）。描述了绝对PTV体积和危及器官剂量的差异。
ITV方法使PTV大小显著减少38%（p<0.0001）。对于中线靶区，ITV方法使双肾平均剂量小幅但有统计学意义地降低了0.8Gy，p = 0.01。采用ITV方法时，心脏和肺的平均剂量平均降低1Gy。采用ITV方法时，非PTV积分剂量从30.4 Gy·L降至27.8 Gy·L。
在儿童中采用ITV方法进行与呼吸相关的器官运动管理，可显著减少绝对PTV体积，维持靶区覆盖，并减少输送到靶区附近正常组织的剂量。这是使包括VMAT在内的高适形放疗技术对该患者群体以及未来质子治疗发挥最大益处的关键一步。
