Zhang Zhe, Li Daming, Peng Feng, Tan Zhibo, Yang Pengfei, Peng Zhaoming, Li Xin, Qi Xinyue, Sun Weixiao, Liu Yajie, Wang Yuenan
Department of Radiation Oncology, Peking University Shenzhen Hospital, Shenzhen, China.
Hong Kong University of Science and Technology Medical Center, Shenzhen-Peking University, Shenzhen, China.
Front Oncol. 2022 Jul 22;12:907181. doi: 10.3389/fonc.2022.907181. eCollection 2022.
Setup error is a key factor affecting postmastectomy radiotherapy (PMRT) and irradiation of the internal mammary lymph nodes is the most investigated aspect for PMRT patients. In this study, we evaluated the robustness, radiobiological, and dosimetric benefits of the hybrid volumetric modulated arc therapy (H-VMAT) planning technique based on the setup error in dose accumulation using a surface-guided system for radiation therapy.
We retrospectively selected 32 patients treated by a radiation oncologist and evaluated the clinical target volume (CTV), including internal lymph node irradiation (IMNIs), and considered the planning target volume (PTV) margin to be 5 mm. Three different planning techniques were evaluated: tangential-VMAT (T-VMAT), intensity-modulated radiation therapy (IMRT), and H-VMAT. The interfraction and intrafraction setup errors were analyzed in each field and the accumulated dose was evaluated as the patients underwent daily surface-guided monitoring. These parameters were included while evaluating CTV coverage, the dose required for the left anterior descending artery (LAD) and the left ventricle (LV), the normal tissue complication probability (NTCP) for the heart and lungs, and the second cancer complication probability (SCCP) for contralateral breast (CB).
When the setup error was accounted for dose accumulation, T-VMAT (95.51%) and H-VMAT (95.48%) had a higher CTV coverage than IMRT (91.25%). In the NTCP for the heart, H-VMAT (0.04%) was higher than T-VMAT (0.01%) and lower than IMRT (0.2%). However, the SCCP (1.05%) of CB using H-VMAT was lower than that using T-VMAT (2%) as well as delivery efficiency. And T-VMAT (3.72) and IMRT (10.5).had higher plan complexity than H-VMAT (3.71).
In this study, based on the dose accumulation of setup error for patients with left-sided PMRT with IMNI, we found that the H-VMAT technique was superior for achieving an optimum balance between target coverage, OAR dose, complication probability, plan robustness, and complexity.
摆位误差是影响乳腺癌改良根治术后放疗（PMRT）的关键因素，而内乳淋巴结照射是PMRT患者研究最多的方面。在本研究中，我们基于使用表面引导放疗系统进行剂量累积时的摆位误差，评估了混合容积调强弧形放疗（H-VMAT）计划技术的稳健性、放射生物学和剂量学优势。
我们回顾性选择了32例由放射肿瘤学家治疗的患者，评估临床靶区（CTV），包括内乳淋巴结照射（IMNIs），并将计划靶区（PTV）边界设定为5毫米。评估了三种不同的计划技术：切线VMAT（T-VMAT）、调强放疗（IMRT）和H-VMAT。分析每个射野的分次间和分次内摆位误差，并在患者接受每日表面引导监测时评估累积剂量。在评估CTV覆盖、左前降支动脉（LAD）和左心室（LV）所需剂量、心脏和肺部的正常组织并发症概率（NTCP）以及对侧乳腺（CB）的二次癌症并发症概率（SCCP）时纳入了这些参数。
当考虑摆位误差进行剂量累积时，T-VMAT（95.51%）和H-VMAT（95.48%）的CTV覆盖率高于IMRT（91.25%）。在心脏的NTCP方面，H-VMAT（0.04%）高于T-VMAT（0.01%）且低于IMRT（0.2%）。然而，使用H-VMAT时CB的SCCP（1.05%）低于使用T-VMAT时（2%）以及照射效率。并且T-VMAT（3.72）和IMRT（10.5）的计划复杂度高于H-VMAT（3.71）。
在本研究中，基于有IMNI的左侧PMRT患者摆位误差的剂量累积，我们发现H-VMAT技术在实现靶区覆盖、危及器官剂量、并发症概率、计划稳健性和复杂度之间的最佳平衡方面更具优势。
