Dept. Of Radiation Oncology, Amsterdam University Medical Centers, the Netherlands.
Dept. Of Radiation Oncology, Amsterdam University Medical Centers, the Netherlands.
Radiother Oncol. 2019 Mar;132:16-22. doi: 10.1016/j.radonc.2018.11.019. Epub 2018 Dec 20.
MR-guided radiation therapy (MRgRT) with daily plan adaptation is a novel but time- and resource-intensive treatment for locally advanced pancreatic cancer (LAPC). We analyzed the benefit in target coverage and organ-at-risk (OAR) sparing of daily plan adaptation in 36 consecutive LAPC patients treated with MRgRT to 40 Gy in 5 fractions.
Adaptive planning was assessed for 180 fractions by comparing non-adapted plans with re-optimized plans using (a) GTV coverage and OAR high-doses, and (b) compliance with institutional objectives for GTV coverage and high-dose OAR constraints. Using these criteria, plan adaptation for each fraction was characterized as "not needed", "beneficial", or "no benefit". Decision-tree analysis was performed to identify subgroups most likely or not to benefit from routine plan adaptation.
The percentage of plans fulfilling institutional constraints increased from 43.9% (non-adapted plans) to 83.3% after online plan adaptation, with significant improvements in GTV coverage and lower V OAR doses. Adaptive re-optimization was found to be "not needed" in 80 fractions (44.4%), "beneficial" in 95 fractions (52.8%) and of "no benefit" in 5 fractions (2.8%). Decision-tree analysis identified a grouping based on distance from tumor to OAR of ≤3 mm and GTV size, respectively, to be the major determinants for the benefit of daily plan adaptation.
MRgRT with daily plan adaptation for LAPC was of benefit in approximately half of fractions, improving target coverage and OAR sparing. Plan adaptation appeared to be relevant mainly in cases where the GTV to adjacent OAR distance was ≤3 mm.
MR 引导的放射治疗（MRgRT）结合每日计划适应性调整是一种治疗局部晚期胰腺癌（LAPC）的新方法，但耗时且资源密集。我们分析了 36 例连续接受 MRgRT 治疗 40Gy 分 5 次的 LAPC 患者中，每日计划适应性调整在靶区覆盖和危及器官（OAR）保护方面的获益。
通过比较非适应性计划和重新优化计划，评估了 180 个分次的适应性计划，使用（a）GTV 覆盖和 OAR 高剂量，以及（b）GTV 覆盖和 OAR 高剂量限制的机构目标符合情况。使用这些标准，对每个分次的计划适应性调整进行了“不需要”、“有益”或“无益”的特征描述。采用决策树分析来确定最有可能或不可能从常规计划适应性调整中获益的亚组。
与非适应性计划相比，机构限制的满足率从 43.9%（非适应性计划）增加到 83.3%（在线计划适应性调整后），GTV 覆盖和 OAR 低剂量体积明显改善。适应性重新优化在 80 个分次中被认为“不需要”（44.4%），在 95 个分次中被认为“有益”（52.8%），在 5 个分次中被认为“无益”（2.8%）。决策树分析确定了基于肿瘤到 OAR 的距离≤3mm 和 GTV 大小的分组，是每日计划适应性调整获益的主要决定因素。
LAPC 的 MRgRT 结合每日计划适应性调整在大约一半的分次中获益，改善了靶区覆盖和 OAR 保护。计划适应性调整主要与 GTV 到相邻 OAR 的距离≤3mm 相关。
