胸段食管癌放疗中降低肺部剂量：VMAT 联合主动呼吸控制用于中度 DIBH。
Reduced lung dose during radiotherapy for thoracic esophageal carcinoma: VMAT combined with active breathing control for moderate DIBH.
机构信息
Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Jinan 250117, China.
出版信息
Radiat Oncol. 2013 Dec 20;8:291. doi: 10.1186/1748-717X-8-291.
BACKGROUND
Lung radiation injury is a critical complication of radiotherapy (RT) for thoracic esophageal carcinoma (EC). Therefore, the goal of this study was to investigate the feasibility and dosimetric effects of reducing the lung tissue irradiation dose during RT for thoracic EC by applying volumetric modulated arc radiotherapy (VMAT) combined with active breathing control (ABC) for moderate deep inspiration breath-hold (mDIBH).
METHODS
Fifteen patients with thoracic EC were randomly selected to undergo two series of computed tomography (CT) simulation scans with ABC used to achieve mDIBH (representing 80% of peak DIBH value) versus free breathing (FB). Gross tumor volumes were contoured on different CT images, and planning target volumes (PTVs) were obtained using different margins. For PTV-FB, intensity-modulated radiotherapy (IMRT) was designed with seven fields, and VMAT included two whole arcs. For PTV-DIBH, VMAT with three 135° arcs was applied, and the corresponding plans were named: IMRT-FB, VMAT-FB, and VMAT-DIBH, respectively. Dosimetric differences between the different plans were compared.
RESULTS
The heart volumes decreased by 19.85%, while total lung volume increased by 52.54% in mDIBH, compared to FB (p < 0.05). The mean conformality index values and homogeneity index values for VMAT-DIBH (0.86, 1.07) were slightly worse than those for IMRT-FB (0.90, 1.05) and VMAT-FB (0.90, 1.06) (p > 0.05). Furthermore, compared to IMRT-FB and VMAT-FB, VMAT-DIBH reduced the mean total lung dose by 18.64% and 17.84%, respectively (p < 0.05); moreover, the V5, V10, V20, and V30 values for IMRT-FB and VMAT-FB were reduced by 10.84% and 10.65% (p > 0.05), 12.5% and 20% (p < 0.05), 30.77% and 33.33% (p < 0.05), and 50.33% and 49.15% (p < 0.05), respectively. However, the heart dose-volume indices were similar between VMAT-DIBH and VMAT-FB which were lower than IMRT-FB without being statistically significant (p > 0.05). The monitor units and treatment time of VMAT-DIBH were also the lowest (p < 0.05).
CONCLUSIONS
VMAT combined with ABC to achieve mDIBH is a feasible approach for RT of thoracic EC. Furthermore, this method has the potential to effectively reduce lung dose in a shorter treatment time and with better targeting accuracy.
背景
肺放射损伤是胸段食管癌（EC）放疗（RT）的一个关键并发症。因此，本研究的目的是通过应用容积旋转调强放疗（VMAT）联合主动呼吸控制（ABC）实现中深度吸气屏气（mDIBH），来探讨在胸段 EC 放疗中降低肺组织照射剂量的可行性和剂量学效果。
方法
随机选择 15 名胸段 EC 患者，分别进行两次 CT 模拟扫描，一次采用 ABC 实现 mDIBH（代表最大 DIBH 值的 80%），一次采用自由呼吸（FB）。在不同的 CT 图像上勾画大体肿瘤体积（GTV），并使用不同的边缘获得计划靶区（PTV）。对于 PTV-FB，设计了七野调强放疗（IMRT），VMAT 包括两个全弧。对于 PTV-DIBH，采用三个 135°的 VMAT 弧，相应的计划分别命名为：IMRT-FB、VMAT-FB 和 VMAT-DIBH。比较不同计划之间的剂量学差异。
结果
与 FB 相比，mDIBH 时心脏体积减少 19.85%，全肺体积增加 52.54%（p<0.05）。VMAT-DIBH 的平均适形指数值和均匀性指数值（0.86，1.07）略低于 IMRT-FB（0.90，1.05）和 VMAT-FB（0.90，1.06）（p>0.05）。此外，与 IMRT-FB 和 VMAT-FB 相比，VMAT-DIBH 分别降低了全肺剂量 18.64%和 17.84%（p<0.05）；而且，IMRT-FB 和 VMAT-FB 的 V5、V10、V20 和 V30 值分别降低了 10.84%和 10.65%（p>0.05），12.5%和 20%（p<0.05），30.77%和 33.33%（p<0.05），50.33%和 49.15%（p<0.05）。然而，VMAT-DIBH 和 VMAT-FB 的心脏剂量体积指数相似，且均低于 IMRT-FB，但差异无统计学意义（p>0.05）。VMAT-DIBH 的监测单位和治疗时间也最低（p<0.05）。
结论
VMAT 联合 ABC 实现 mDIBH 是胸段 EC RT 的一种可行方法。此外，这种方法有可能在更短的治疗时间内，以更高的靶向准确性，有效地降低肺剂量。
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