Qi X Sharon, Liu Tian X, Liu Arthur K, Newman Francis, Rabinovitch Rachel, Kavanagh Brian, Hu Y Angie
Department of Radiation Oncology, University of California Los Angeles, Los Angeles, CA.
Department of Radiology, Baylor College of Medicine, Houston, TX.
Med Dosim. 2014 Autumn;39(3):227-34. doi: 10.1016/j.meddos.2014.02.005. Epub 2014 May 23.
The 3-dimensional conformal radiotherapy (3DCRT) technique is the standard for breast cancer radiotherapy. During treatment planning, not only the coverage of the planning target volume (PTV) but also the minimization of the dose to critical structures, such as the lung, heart, and contralateral breast tissue, need to be considered. Because of the complexity and variations of patient anatomy, more advanced radiotherapy techniques are sometimes desired to better meet the planning goals. In this study, we evaluated external-beam radiation treatment techniques for left breast cancer using various delivery platforms: fixed-field including TomoDirect (TD), static intensity-modulated radiotherapy (sIMRT), and rotational radiotherapy including Elekta volumetric-modulated arc therapy (VMAT) and tomotherapy helical (TH). A total of 10 patients with left-sided breast cancer who did or did not have positive lymph nodes and were previously treated with 3DCRT/sIMRT to the entire breast were selected, their treatment was planned with Monaco VMAT, TD, and TH. Dosimetric parameters including PTV coverage, organ-at-risk (OAR) sparing, dose-volume histograms, and target minimum/maximum/mean doses were evaluated. It is found that for plans providing comparable PTV coverage, the Elekta VMAT plans were generally more inhomogeneous than the TH and TD plans. For the cases with regional node involvement, the average mean doses administered to the heart were 9.2 (± 5.2) and 8.8 (± 3.0)Gy in the VMAT and TH plans compared with 11.9 (± 6.4) and 11.8 (± 9.2)Gy for the 3DCRT and TD plans, respectively, with slightly higher doses given to the contralateral lung or breast or both. On average, the total monitor units for VMAT plans are 11.6% of those TH plans. Our studies have shown that VMAT and TH plans offer certain dosimetric advantages over fixed-field IMRT plans for advanced breast cancer requiring regional nodal treatment. However, for early-stage breast cancer fixed-field radiotherapy is potentially more beneficial in terms of OAR sparing.
三维适形放疗（3DCRT）技术是乳腺癌放疗的标准方法。在治疗计划制定过程中，不仅要考虑计划靶区（PTV）的覆盖情况，还需要考虑将对关键结构（如肺、心脏和对侧乳腺组织）的剂量降至最低。由于患者解剖结构的复杂性和变异性，有时需要更先进的放疗技术来更好地实现计划目标。在本研究中，我们评估了使用各种放疗设备的左侧乳腺癌外照射治疗技术：包括TomoDirect（TD）的固定野、静态调强放疗（sIMRT）以及包括医科达容积调强弧形放疗（VMAT）和螺旋断层放疗（TH）的旋转放疗。总共选取了10例左侧乳腺癌患者，这些患者有或没有阳性淋巴结，且之前接受过全乳3DCRT/sIMRT治疗，用Monaco VMAT、TD和TH为他们制定治疗计划。评估了包括PTV覆盖、危及器官（OAR）保护、剂量体积直方图以及靶区最小/最大/平均剂量等剂量学参数。结果发现，对于提供可比PTV覆盖的计划，医科达VMAT计划通常比TH和TD计划的剂量分布更不均匀。对于有区域淋巴结受累的病例，VMAT和TH计划中给予心脏 的平均剂量分别为9.2（±5.2）和8.8（±3.0）Gy，而3DCRT和TD计划分别为11.9（±6.4）和11.8（±9.2）Gy，对侧肺或乳腺或两者的剂量略高。平均而言，VMAT计划的总监测单位是TH计划的11.6%。我们的研究表明，对于需要区域淋巴结治疗的晚期乳腺癌，VMAT和TH计划在剂量学方面比固定野调强放疗计划具有一定优势。然而，对于早期乳腺癌，固定野放疗在保护OAR方面可能更有益。
