Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan, USA.
Int J Radiat Oncol Biol Phys. 2013 Aug 1;86(5):956-63. doi: 10.1016/j.ijrobp.2013.05.003.
This study aimed to compare lung dose-volume histogram (DVH) parameters such as mean lung dose (MLD) and the lung volume receiving ≥20 Gy (V20) of commonly used definitions of normal lung in terms of tumor/target subtraction and to determine to what extent they differ in predicting radiation pneumonitis (RP).
One hundred lung cancer patients treated with definitive radiation therapy were assessed. The gross tumor volume (GTV) and clinical planning target volume (PTVc) were defined by the treating physician and dosimetrist. For this study, the clinical target volume (CTV) was defined as GTV with 8-mm uniform expansion, and the PTV was defined as CTV with an 8-mm uniform expansion. Lung DVHs were generated with exclusion of targets: (1) GTV (DVHG); (2) CTV (DVHC); (3) PTV (DVHP); and (4) PTVc (DVHPc). The lung DVHs, V20s, and MLDs from each of the 4 methods were compared, as was their significance in predicting radiation pneumonitis of grade 2 or greater (RP2).
There are significant differences in dosimetric parameters among the various definition methods (all Ps<.05). The mean and maximum differences in V20 are 4.4% and 12.6% (95% confidence interval 3.6%-5.1%), respectively. The mean and maximum differences in MLD are 3.3 Gy and 7.5 Gy (95% confidence interval, 1.7-4.8 Gy), respectively. MLDs of all methods are highly correlated with each other and significantly correlated with clinical RP2, although V20s are not. For RP2 prediction, on the receiver operating characteristic curve, MLD from DVHG (MLDG) has a greater area under curve of than MLD from DVHC (MLDC) or DVHP (MLDP). Limiting RP2 to 30%, the threshold is 22.4, 20.6, and 18.8 Gy, for MLDG, MLDC, and MLDP, respectively.
The differences in MLD and V20 from various lung definitions are significant. MLD from the GTV exclusion method may be more accurate in predicting clinical significant radiation pneumonitis.
本研究旨在比较常用的正常肺定义（基于肿瘤/靶区减影）中肺剂量-体积直方图（DVH）参数，如平均肺剂量（MLD）和接受 20Gy 及以上剂量的肺体积（V20），并确定它们在预测放射性肺炎（RP）方面的差异程度。
评估了 100 例接受根治性放疗的肺癌患者。GTV 和临床计划靶区（PTVc）由治疗医师和剂量师定义。对于本研究，CTV 定义为 GTV 加 8mm 均匀扩张，PTV 定义为 CTV 加 8mm 均匀扩张。生成排除靶区后的肺 DVH：（1）GTV（DVHG）；（2）CTV（DVHC）；（3）PTV（DVHP）；和（4）PTVc（DVHPc）。比较了这 4 种方法的肺 DVH、V20 和 MLD，并比较了它们在预测 2 级及以上放射性肺炎（RP2）中的意义。
不同定义方法之间的剂量学参数存在显著差异（均 P<.05）。V20 的平均和最大差异分别为 4.4%和 12.6%（95%置信区间 3.6%-5.1%）。MLD 的平均和最大差异分别为 3.3Gy 和 7.5Gy（95%置信区间 1.7-4.8Gy）。所有方法的 MLD 均高度相关，与临床 RP2 显著相关，而 V20 则不相关。对于 RP2 预测，在接收器工作特征曲线中，DVHG 中的 MLD（MLDG）的曲线下面积大于 DVHC 中的 MLD（MLDC）或 DVHP 中的 MLD（MLDP）。将 RP2 限制在 30%，MLDG、MLDC 和 MLDP 的阈值分别为 22.4、20.6 和 18.8Gy。
不同肺定义的 MLD 和 V20 差异显著。基于 GTV 排除法的 MLD 可能更能准确预测临床显著放射性肺炎。
