Department of Radiation Oncology, Kumamoto University Hospital, Kumamoto, Japan.
J Radiat Res. 2010;51(6):691-8. doi: 10.1269/jrr.10084. Epub 2010 Oct 6.
This study aimed to identify factors predictive of the benefit of respiratory-gated radiotherapy. Three plans were created for 25 patients with non-small cell lung cancer, simulating the following 3 treatment scenarios. Protocol 1 was non-gated and the lung dose was calculated using 4-s slow CT (PnA), protocol 2 was also non-gated and the lung dose was calculated by CT at the end-expiration phase (PnE), and protocol 3 applied phase-based gating around end-expiration (PgE). We correlated possible predictive factors with the estimated lung dose reduction achieved by respiratory gating. The 3D clinical target volume (CTV) motion, craniocaudal CTV motion, and the craniocaudal CTV position were correlated with the reduction in V20 and the mean lung dose (p < 0.01). CTV was not significantly correlated with the estimated lung dose reduction. The area under the ROC curve (AUC) for 3D- and craniocaudal CTV motion, and craniocaudal CTV position was 1.000, 0.997, and 0.943, respectively, when the threshold for selecting patients was set at a 1% reduction of V20 and at a 0.5 Gy reduction in the mean lung dose. The results of the present study suggest that 3D CTV motion, craniocaudal CTV motion, and the craniocaudal CTV position are useful for predicting the benefit of respiratory-gated radiotherapy in lung cancer patients.
本研究旨在确定预测呼吸门控放疗获益的因素。为 25 名非小细胞肺癌患者创建了三个计划，模拟了以下三种治疗情况。方案 1 是非门控的，使用 4 秒慢 CT（PnA）计算肺剂量；方案 2 也是非门控的，使用呼气末相 CT（PnE）计算肺剂量；方案 3 在呼气末相应用基于相位的门控（PgE）。我们将可能的预测因素与呼吸门控实现的肺剂量降低相关联。3D 临床靶区（CTV）运动、头脚方向 CTV 运动和头脚方向 CTV 位置与 V20 和平均肺剂量的降低呈正相关（p<0.01）。CTV 与估计的肺剂量降低无显著相关性。当选择患者的阈值设定为 V20 降低 1%和平均肺剂量降低 0.5Gy 时，3D-CTV 运动、头脚方向 CTV 运动和头脚方向 CTV 位置的 ROC 曲线下面积（AUC）分别为 1.000、0.997 和 0.943。本研究结果表明，3D CTV 运动、头脚方向 CTV 运动和头脚方向 CTV 位置有助于预测肺癌患者呼吸门控放疗的获益。
