Department of Radiation Medicine, University of Kentucky, Lexington, Kentucky, USA.
J Appl Clin Med Phys. 2023 Sep;24(9):e14047. doi: 10.1002/acm2.14047. Epub 2023 May 23.
The aim of this study was to demonstrate the feasibility and efficacy of an iterative CBCT-guided breast radiotherapy with Fast-Forward trial of 26 Gy in five fractions on a Halcyon Linac. This study quantifies Halcyon plan quality, treatment delivery accuracy and efficacy by comparison with those of clinical TrueBeam plans.
Ten accelerated partial breast irradiation (APBI) patients (four right, six left) who underwent Fast-Forward trial at our institute on TrueBeam (6MV beam) were re-planned on Halcyon (6MV-FFF). Three site-specific partial coplanar VMAT arcs and an Acuros-based dose engine were used. For benchmarking, PTV coverage, organs-at-risk (OAR) doses, beam-on time, and quality assurance (QA) results were compared for both plans.
The average PTV was 806 cc. Compared to TrueBeam plans, Halcyon provided highly conformal and homogeneous plans with similar mean PTVD95 (25.72 vs. 25.73 Gy), both global maximum hotspot < 110% (p = 0.954) and similar mean GTV dose (27.04 vs. 26.80 Gy, p = 0.093). Halcyon provided lower volume of ipsilateral lung receiving 8 Gy (6.34% vs. 8.18%, p = 0.021), similar heart V1.5 Gy (16.75% vs. 16.92%, p = 0.872), V7Gy (0% vs. 0%), mean heart dose (0.96 vs. 0.9 Gy, p = 0.228), lower maximum dose to contralateral breast (3.2 vs. 3.6 Gy, p = 0.174), and nipple (19.6 vs. 20.1 Gy, p = 0.363). Compared to TrueBeam, Halcyon plans provided similar patient-specific QA pass rates and independent in-house Monte Carlo second check results of 99.6% vs. 97.9% (3%/2 mm gamma criteria) and 98.6% versus 99.2%, respectively, suggesting similar treatment delivery accuracy. Halcyon provided shorter beam-on time (1.49 vs. 1.68 min, p = 0.036).
Compared to the SBRT-dedicated TrueBeam, Halcyon VMAT plans provided similar plan quality and treatment delivery accuracy, yet potentially faster treatment via one-step patient setup and verification with no patient collision issues. Rapid delivery of daily APBI on Fast-Forward trial on Halcyon with door-to-door patient time < 10 min, could reduce intrafraction motion errors, and improve patient comfort and compliance. We have started treating APBI on Halcyon. Clinical follow-up results are warranted. We recommend Halcyon users consider implementing the protocol to remote and underserved APBI patients in Halcyon-only clinics.
本研究旨在展示在 Halcyon 直线加速器上进行 26 Gy 五次分割的 Fast-Forward 试验中迭代 CBCT 引导下乳腺癌放射治疗的可行性和疗效。本研究通过与临床 TrueBeam 计划的比较，量化了 Halcyon 计划的质量、治疗交付的准确性和疗效。
在我们机构的 TrueBeam（6MV 射线）上进行 Fast-Forward 试验的 10 名加速部分乳房照射（APBI）患者（4 名右侧，6 名左侧）在 Halcyon（6MV-FFF）上重新进行计划。使用了三个特定部位的部分共面 VMAT 弧形和基于 Acuros 的剂量引擎。为了进行基准测试，比较了两种计划的 PTV 覆盖、危及器官（OAR）剂量、射束开启时间和质量保证（QA）结果。
平均 PTV 为 806 cc。与 TrueBeam 计划相比，Halcyon 提供了高度适形和均匀的计划，具有相似的平均 PTVD95（25.72 与 25.73 Gy），两者的全局最大热点均<110%（p=0.954），且相似的 GTV 剂量均值（27.04 与 26.80 Gy，p=0.093）。Halcyon 使同侧肺接受 8 Gy 的体积更小（6.34%与 8.18%，p=0.021），相似的心脏 V1.5 Gy（16.75%与 16.92%，p=0.872），V7Gy（0%与 0%），平均心脏剂量（0.96 与 0.9 Gy，p=0.228），对对侧乳房的最大剂量更低（3.2 与 3.6 Gy，p=0.174），以及乳头（19.6 与 20.1 Gy，p=0.363）。与 TrueBeam 相比，Halcyon 计划提供了相似的患者特异性 QA 通过率和独立内部蒙特卡罗二次检查结果，分别为 99.6%与 97.9%（3%/2mm 伽马标准）和 98.6%与 99.2%，提示治疗交付的准确性相似。Halcyon 提供的射束开启时间更短（1.49 与 1.68 分钟，p=0.036）。
与专门用于 SBRT 的 TrueBeam 相比，Halcyon VMAT 计划提供了相似的计划质量和治疗交付准确性，但通过一步式患者设置和验证，潜在地更快治疗，且没有患者碰撞问题。在 Halcyon 上快速进行 Fast-Forward 试验的每日 APBI 治疗，门到门患者时间<10 分钟，可减少分次内运动误差，提高患者舒适度和依从性。我们已经开始在 Halcyon 上治疗 APBI。需要临床随访结果。我们建议 Halcyon 用户考虑为仅在 Halcyon 诊所的远程和服务不足的 APBI 患者实施该方案。
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