Fang Yingtao, Yu Wenliang, Qiao Jian, Yang Yanju, Mi Jing, Yu Lei, Guo Ying, Wang Jiazhou, Hu Weigang
Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.
Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China.
Technol Cancer Res Treat. 2025 Jan-Dec;24:15330338251363288. doi: 10.1177/15330338251363288. Epub 2025 Jul 25.
IntroductionLeft-sided breast cancer radiotherapy requires precise dose modulation to balance target coverage and organ-at-risk (OAR) sparing. This study evaluates a novel Organ and Arc-based Directional Block (OABD Block) in helical tomotherapy planning to address this challenge.MethodsIn this single-institutional retrospective study, 10 post-mastectomy patients with left-sided breast cancer receiving adjuvant radiotherapy were studied. Target volumes included chest wall, internal mammary, axillary, and supraclavicular lymph nodes, with a dose of 50 Gy over 25 fractions. Using a tomotherapy planning system, an OABD Block was configured to incorporate arc structures and protect organs-at-risk. For each patient, helical tomotherapy plans were prepared with and without the OABD Block, keeping field width, pitch, and modulation factors identical. Additionally, static intensity-modulated radiotherapy (IMRT) plans were created on a United Imaging system. Treatment plans were evaluated by dose-volume parameters, conformity and homogeneity indices, and mean doses to targets and normal tissues.ResultsHelical tomotherapy with the OABD Block provided a mean conformity Index of 0.79 for the Planning Target Volume, higher than plans without the block (0.73) but below IMRT plans (0.88). The homogeneity Index averaged 0.14 with the block, 0.18 without, and 0.11 in IMRT. For the internal mammary lymph node region, D95% reached 5007.7 cGy with the block, compared to 5001.1 cGy without and 4897.9 cGy in IMRT. The OABD Block reduced the mean heart dose to 478.7 cGy, compared to 533.5 cGy without and 638.9 cGy in IMRT. Left lung V5 was 48.0% with the block, 52.7% without, and 53.2% in IMRT; V20 was also lowest with the block (17.5%) versus without (20.3%) and IMRT (24.3%).ConclusionAdding the OABD Block to helical tomotherapy improved internal mammary lymph node dose coverage and reduced exposure to organs at risk.
引言
左侧乳腺癌放疗需要精确的剂量调制，以平衡靶区覆盖和危及器官（OAR）的保护。本研究评估了螺旋断层放疗计划中一种新型的基于器官和弧的定向挡块（OABD挡块），以应对这一挑战。
方法
在这项单机构回顾性研究中，对10例接受辅助放疗的左侧乳腺癌乳房切除术后患者进行了研究。靶区包括胸壁、内乳、腋窝和锁骨上淋巴结，剂量为50 Gy，分25次照射。使用断层放疗计划系统，配置一个OABD挡块以纳入弧形结构并保护危及器官。对于每位患者，分别制备有和没有OABD挡块的螺旋断层放疗计划，保持射野宽度、螺距和调制因子相同。此外，在联影系统上创建静态调强放疗（IMRT）计划。通过剂量体积参数、适形度和均匀性指数以及靶区和正常组织的平均剂量来评估治疗计划。
结果
使用OABD挡块的螺旋断层放疗为计划靶区提供的平均适形指数为0.79，高于没有该挡块的计划（0.73），但低于IMRT计划（0.88）。有挡块时均匀性指数平均为0.14，无挡块时为0.18，IMRT为0.11。对于内乳淋巴结区域，有挡块时D95%达到5007.7 cGy，无挡块时为5001.1 cGy，IMRT为4897.9 cGy。OABD挡块将心脏平均剂量降低至478.7 cGy，无挡块时为533.5 cGy，IMRT为638.9 cGy。有挡块时左肺V5为48.0%，无挡块时为52.7%，IMRT为53.2%；有挡块时V20也最低（17.5%），无挡块时为（20.3%），IMRT为（24.3%）。
结论
在螺旋断层放疗中添加OABD挡块可改善内乳淋巴结剂量覆盖，并减少对危及器官的照射。
