Lei Runhong, Zhang Xile, Li Jinna, Sun Haitao, Yang Ruijie
Department of Radiation Oncology, Peking University Third Hospital, Beijing, China.
Front Oncol. 2021 Jul 8;11:702171. doi: 10.3389/fonc.2021.702171. eCollection 2021.
To improve the quality of plan for the radiation treatment of advanced left breast cancer by introducing the auxiliary structures (ASs) which are used to spare the regions with no intact delineated structures adjacent to the target volume.
CT data from 20 patients with left-sided advanced breast cancer were selected. An AS designated as A1 was created to spare the regions of the aorta, pulmonary artery, superior vena ava, and contralateral tissue of the upper chest and neck, and another, designated as A2, was created in the regions of the cardia and fundus of the stomach, left liver lobe, and splenic flexure of the colon. IMRT and VMAT plans were created for cases with and without the use of the AS dose constraints in plan optimization. Dosimetric parameters of the target and organs at risk (OARs) were compared between the separated groups.
With the use of AS dose constraints, both the IMRT and VMAT plans were clinically acceptable and deliverable, even showing a slight improvement in dose distribution of both the target and OARs compared with the AS-unused plans. The ASs significantly realized the dose sparing for the regions and brought a better conformity index ( < 0.05) and homogeneity index ( < 0.05) in VMAT plans. In addition, the volume receiving at least 20 Gy (V) for the heart ( < 0.05), V for the left lung ( < 0.05), and V for the axillary-lateral thoracic vessel juncture region ( < 0.05) were all lower in VMAT plans.
The use of the defined AS dose constraints in plan optimization was effective in sparing the indicated regions, improving the target dose distribution, and sparing OARs for advanced left breast cancer radiotherapy, especially those that utilize VMAT plans.
通过引入辅助结构（ASs）来提高晚期左乳腺癌放射治疗计划的质量，这些辅助结构用于保护靶区周围没有完整勾画结构的区域。
选取20例左侧晚期乳腺癌患者的CT数据。创建一个名为A1的辅助结构以保护主动脉、肺动脉、上腔静脉以及上胸部和颈部的对侧组织区域，另一个名为A2的辅助结构创建于贲门、胃底、左肝叶和结肠脾曲区域。在计划优化过程中，分别为使用和不使用AS剂量约束的病例创建调强放疗（IMRT）和容积调强弧形放疗（VMAT）计划。比较不同分组中靶区和危及器官（OARs）的剂量学参数。
使用AS剂量约束时，IMRT和VMAT计划在临床上均可接受且可实施，与未使用AS的计划相比，靶区和OARs的剂量分布甚至有轻微改善。辅助结构显著实现了对相关区域的剂量 sparing，并在VMAT计划中带来了更好的适形指数（<0.05）和均匀性指数（<0.05）。此外，VMAT计划中心脏接受至少20 Gy（V）的体积（<0.05）、左肺的V（<0.05）以及腋窝-胸外侧血管交界区域的V（<0.05）均更低。
在计划优化中使用定义的AS剂量约束可有效保护指定区域，改善靶区剂量分布，并在晚期左乳腺癌放疗中保护OARs，尤其是那些采用VMAT计划的情况。
