Gram Vanja Remberg, Gram Daniel, Persson Gitte Fredberg, Suppli Morten Hiul, Barrett Sarah
Department of Oncology, Section of Radiotherapy, Rigshospitalet, University Hospital of Copenhagen, Denmark.
Department of Oncology, University Hospital Herlev-Gentofte Hospital, Copenhagen, Denmark.
Tech Innov Patient Support Radiat Oncol. 2022 Jul 16;23:8-14. doi: 10.1016/j.tipsro.2022.07.001. eCollection 2022 Sep.
Palliative radiotherapy for metastatic spinal cord compression (MSCC) is given to halt disease progression and sustain quality of life for patients with advanced cancer. Radiotherapy can however induce toxicity, contradicting treatment intention. Advanced radiotherapy offers possibility of sparing organs at risk (OARs). The purpose of this dosimetric study is to establish the feasibility and potential benefits of dose sparing of the oesophagus.
30 patients receiving radiotherapy of 30 Gy/10# for MSCC were retrospectively included and the oesophagus delineated. Two new dose plans were created for each patient (eso-crop and PTV-crop) with the intention of optimising the oesophageal dose. In the eso-crop plan maintaining full target volume coverage was prioritised, for the PTV-crop plan oesophageal dose was further reduced through cropping the planning target volume (PTV) overlapping oesophageal/PTV-area. Time added for delineation was measured. Plans were compared using Wilcoxon signed rank test with p < 0.05 considered statistically significant. Bivariate associations between dose metrics and patient characteristics were quantified using linear regression models.
Oesophageal delineation took a mean of 8.6 min. There was significant dose reduction for both V7.7 Gy, D2% and mean oesophageal dose, without significant change in CTV coverage. The mean achievable oesophageal dose reduction was 29.1% and 50.4% for the eso-crop and PTV crop plans, respectively. Minor changes in dose distribution to the lungs was observed, with increased mean and V20Gy for the eso-crop plan and decreased V5Gy to the PTV-crop plan.
This study demonstrated the possibility of significant dose sparing of the oesophageal dose using single arc VMAT without impacting on CTV coverage.
转移性脊髓压迫症（MSCC）的姑息性放疗旨在阻止疾病进展并维持晚期癌症患者的生活质量。然而，放疗可能会引发毒性反应，与治疗目的相悖。先进的放疗技术为保护危及器官（OARs）提供了可能。本剂量学研究的目的是确定食管剂量 sparing 的可行性和潜在益处。
回顾性纳入 30 例接受 30 Gy/10 次分割放疗的 MSCC 患者，并勾勒出食管轮廓。为每位患者创建了两个新的剂量计划（食管裁剪和计划靶体积裁剪），旨在优化食管剂量。在食管裁剪计划中，优先保持全靶区覆盖；对于计划靶体积裁剪计划，通过裁剪与食管/计划靶体积区域重叠的计划靶体积（PTV）来进一步降低食管剂量。测量勾勒轮廓所增加的时间。使用 Wilcoxon 符号秩检验比较计划，p < 0.05 被认为具有统计学意义。使用线性回归模型量化剂量指标与患者特征之间的双变量关联。
食管勾勒平均耗时 8.6 分钟。V7.7 Gy、D2%和平均食管剂量均显著降低，而临床靶区（CTV）覆盖无显著变化。食管裁剪计划和计划靶体积裁剪计划的平均可实现食管剂量降低分别为 29.1%和 50.4%。观察到肺部剂量分布有微小变化，食管裁剪计划的平均剂量和 V20Gy 增加，计划靶体积裁剪计划的 V5Gy 降低。
本研究表明，使用单弧容积调强放疗（VMAT）在不影响 CTV 覆盖的情况下，有可能显著降低食管剂量。
