Sha Xue, Duan Jinghao, Lin Xiutong, Zhu Jian, Zhang Ruohui, Sun Tao, Wang Hui, Meng Xiangjuan, Yin Yong
Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China.
Shandong Provincial Key Laboratory of Digital Medicine and Computer-Assisted Surgery, Qingdao, China.
Front Oncol. 2021 Feb 2;10:611514. doi: 10.3389/fonc.2020.611514. eCollection 2020.
Whole lung irradiation (WLI) plays a crucial role in local control in pediatric patients with lung metastases and improves patient survival. The intention of this research was to explore the advantage of cardiac sparing between photons and protons during WLI. We also propose a new solution for cardiac sparing with proton techniques.
Eleven patients with pediatric tumors and pulmonary metastasis treated with 12 Gy WLI (all received volumetric-modulated arc therapy (VMAT)) in our institute between 2010 and 2019 were retrospectively selected. Each patient was replanned with intensity-modulated radiation therapy (IMRT), helical tomotherapy (HT), and two intensity-modulated proton radiotherapy (IMPT) plans (IMPT-1 and IMPT-2). IMPT-1 considered the whole lung as the planning target volume (PTV), utilizing the anteroposterior technique (0/180°). IMPT-2 was a new proton solution that we proposed in this research. This approach considered the unilateral lung as the PTV, and 3 ipsilateral fields were designed for each lung. Then, IMPT-2 was generated by summing two unilateral lung plans. The primary objective was to obtain adequate coverage (95% of the prescription dose to the PTV) while maximally sparing the dose to the heart. The PTV coverage, conformity index (CI), homogeneity index (HI), and dose-volume statistics of the heart and substructures were assessed by means of the averages of each comparison parameter.
All treatment techniques achieved the target volume coverage required by clinical practice. HT yielded the best coverage and homogeneity for the target structure compared with other techniques. The CI from IMRT was excellent. For photon radiation therapy, the HT plan afforded superior dose sparing for the V, V, V, V, and D of the heart and D of the right ventricle (RV). IMRT displayed the most notable dose reductions in the V, V, V, and V of the heart and D of the right atrium (RA). The VMAT plan was the least effective on the heart and substructures. However, compared with photon radiation therapy, IMPT-1 did not show an advantage for heart protection. Interestingly, IMPT-2 provided significant superiority in cardiac sparing, including maximum dose sparing for the V, V, V, V, V and D of the heart and D of the RA, RV, left atrium (LA) and left ventricle (LV) compared to all other techniques.
Considering the complex anatomical relation between target volumes and organs at risk (OARs), IMPT can provide a dose advantage for organs located outside of the target area rather than within or surrounding the area. It is hoped that advances in proton therapy (PT) plan design will lead to further improvements in radiotherapy approaches and provide the best treatment choice for individual patients.
全肺照射（WLI）在小儿肺转移瘤患者的局部控制中起着关键作用，并能提高患者生存率。本研究旨在探讨WLI期间光子和质子在心脏保护方面的优势。我们还提出了一种利用质子技术进行心脏保护的新方案。
回顾性选取2010年至2019年在我院接受12 Gy WLI治疗（均接受容积调强弧形放疗（VMAT））的11例小儿肿瘤伴肺转移患者。对每位患者分别采用调强放射治疗（IMRT）、螺旋断层放疗（HT）以及两种调强质子放疗（IMPT）计划（IMPT-1和IMPT-2）进行重新计划。IMPT-1将全肺作为计划靶区（PTV），采用前后向技术（0/180°）。IMPT-2是我们在本研究中提出的一种新的质子方案。该方法将单侧肺作为PTV，为每侧肺设计3个同侧野。然后，通过将两个单侧肺计划相加生成IMPT-2。主要目的是在最大程度减少心脏受量的同时获得足够的靶区覆盖（PTV接受95%的处方剂量）。通过各比较参数的平均值评估PTV覆盖情况、适形指数（CI）、均匀性指数（HI）以及心脏和亚结构的剂量体积统计数据。
所有治疗技术均达到了临床实践要求的靶区覆盖。与其他技术相比，HT对靶区结构的覆盖和均匀性最佳。IMRT的CI极佳。对于光子放射治疗，HT计划在心脏的V、V、V、V以及右心室（RV）的D和右心房（RA）的D方面提供了更好的剂量 sparing。IMRT在心脏的V、V、V、V以及右心房的D方面显示出最显著的剂量降低。VMAT计划对心脏和亚结构的效果最差。然而，与光子放射治疗相比，IMPT-1在心脏保护方面未显示出优势。有趣的是，与所有其他技术相比，IMPT-2在心脏保护方面具有显著优势，包括在心脏的V、V、V、V、V以及RA、RV、左心房（LA）和左心室（LV）的D方面实现了最大剂量 sparing。
考虑到靶区与危及器官（OARs）之间复杂的解剖关系，IMPT可为位于靶区外而非靶区内或靶区周围的器官提供剂量优势。希望质子治疗（PT）计划设计的进展将进一步改善放射治疗方法，并为个体患者提供最佳治疗选择。
