Christian Judith A, Bedford James L, Webb Steve, Brada Michael
The Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Sutton, United Kingdom.
Int J Radiat Oncol Biol Phys. 2007 Mar 1;67(3):735-41. doi: 10.1016/j.ijrobp.2006.09.047. Epub 2006 Dec 21.
Lungs are the major dose-limiting organ during radiotherapy (RT) for non-small-cell lung cancer owing to the development of pneumonitis. This study compared intensity-modulated RT (IMRT) with three-dimensional conformal RT (3D-CRT) in reducing the dose to the lungs.
Ten patients with localized non-small-cell lung cancer underwent computed tomography (CT). The planning target volume (PTV) was defined and the organs at risk were outlined. An inverse-planning program, AutoPlan, was used to design the beam angle-optimized six-field noncoplanar 3D-CRT plans. Each 3D-CRT plan was compared with a series of five IMRT plans per patient. The IMRT plans were created using a commercial algorithm and consisted of a series of three, five, seven, and nine equidistant coplanar field arrangements and one six-field noncoplanar plan. The planning objectives were to minimize the lung dose while maintaining the dose to the PTV. The percentage of lung volume receiving >20 Gy (V20) and the percentage of the PTV covered by the 90% isodose (PTV90) were the primary endpoints. The PTV90/V20 ratio was used as the parameter accounting for both the reduction in lung volume treated and the PTV coverage.
All IMRT plans, except for the three-field coplanar plans, improved the PTV90/V20 ratio significantly compared with the optimized 3D-CRT plan. Nine coplanar IMRT beams were significantly better than five or seven coplanar IMRT beams, with an improved PTV90/V20 ratio.
The results of our study have shown that IMRT can reduce the dose to the lungs compared with 3D-CRT by improving the conformity of the plan.
由于放射性肺炎的发生，肺部是非小细胞肺癌放射治疗（RT）期间的主要剂量限制器官。本研究比较了调强放疗（IMRT）与三维适形放疗（3D-CRT）在减少肺部剂量方面的效果。
10例局限性非小细胞肺癌患者接受了计算机断层扫描（CT）检查。定义了计划靶体积（PTV）并勾勒出危及器官。使用逆向计划程序AutoPlan设计束角优化的六野非共面3D-CRT计划。将每个3D-CRT计划与每位患者的一系列五个IMRT计划进行比较。IMRT计划使用商业算法创建，包括一系列三个、五个、七个和九个等距共面野排列以及一个六野非共面计划。计划目标是在保持PTV剂量的同时尽量减少肺部剂量。接受>20 Gy的肺体积百分比（V20）和90%等剂量线覆盖的PTV百分比（PTV90）是主要终点。PTV90/V20比值用作兼顾治疗的肺体积减少和PTV覆盖情况的参数。
除三野共面计划外，所有IMRT计划与优化的3D-CRT计划相比，PTV90/V20比值均有显著改善。九个共面IMRT射束明显优于五个或七个共面IMRT射束，PTV90/V20比值有所提高。
我们的研究结果表明，与3D-CRT相比，IMRT可通过改善计划的适形性来减少肺部剂量。
