Hirotaki Kouta, Motegi Kana, Moriya Shunsuke, Wakabayashi Masashi, Sakae Takeji, Ito Masashi, Zenda Sadamoto
Doctoral Program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan.
Department of Radiological Technology, National Cancer Center Hospital East, Chiba, Japan.
J Appl Clin Med Phys. 2025 Aug;26(8):e70194. doi: 10.1002/acm2.70194.
Studies suggest that integrating robust planning and noncoplanar volumetric modulated arc therapy (VMAT) may be a useful strategy for maximizing the benefits of dose delivery while maintaining resilience to uncertainty; however, the robustness of target coverage and the dose-sparing performance for organs at risk of techniques that combine dynamic trajectory irradiation and robust planning have not been fully investigated.
We aimed to evaluate the combination of biaxially rotational dynamic radiation therapy (BROAD-RT) with robust planning to improve the dosimetric outcomes and robustness of head and neck cancer (HNC) radiation therapy.
We retrospectively analyzed 10 patients with oropharyngeal and hypopharyngeal cancers who were treated with VMAT. Robust-VMAT, Robust-Non-Coplanar-VMAT (Robust-NC-VMAT), and Robust-BROAD-RT plans were generated using the RayStation treatment planning system, with patient setup uncertainties of 3-5 mm in each of the three axial directions (left-right, anterior-posterior, and superior-inferior) applied to the clinical target volume (CTV) during robust optimization. The prescribed doses were 70 and 56 Gy in 35 fractions for high- and low-risk CTVs, respectively. Dosimetric parameters, including dose coverage for the CTVs and organ at risk (OAR) sparing, were compared between the plans. Robustness was evaluated using eight uncertainty scenarios, each generated by applying ± 1.7 mm translational shifts simultaneously along all three orthogonal axes (left-right, anterior-posterior, and superior-inferior), resulting in a combined vector displacement of approximately 3 mm.
The Robust-BROAD-RT plans significantly reduced the mean doses to the contralateral and ipsilateral parotid glands and the oral cavity by 8.17, 6.20, and 3.03 Gy, respectively, compared to the Robust-VMAT plans (p < 0.001, p < 0.001, and p = 0.002, respectively). Similarly, the Robust-BROAD-RT plans achieved significantly lower doses to the parotid glands and the oral cavity compared to the Robust-NC-VMAT plans (p = 0.004, p = 0.014, and p = 0.014, respectively). No significant differences were observed in the target coverage indices (D98, D50), conformity index (CI), or homogeneity index (HI) among the three techniques. The worst-case scenario analysis showed that the degree of deterioration in these target-related parameters did not differ significantly among the Robust-BROAD-RT, Robust-VMAT, and Robust-NC-VMAT plans.
The Robust-BROAD-RT plan achieved a further reduction in doses to the parotid and oral cavities while maintaining robustness comparable to that of conventional Robust VMAT planning.
研究表明，整合稳健计划与非共面容积调强弧形放疗（VMAT）可能是一种有用的策略，可在保持对不确定性的适应性的同时，最大化剂量递送的益处；然而，结合动态轨迹照射和稳健计划的技术对危及器官的靶区覆盖稳健性和剂量 sparing 性能尚未得到充分研究。
我们旨在评估双轴旋转动态放射治疗（BROAD-RT）与稳健计划相结合，以改善头颈癌（HNC）放射治疗的剂量学结果和稳健性。
我们回顾性分析了 10 例接受 VMAT 治疗的口咽癌和下咽癌患者。使用 RayStation 治疗计划系统生成稳健 VMAT、稳健非共面 VMAT（Robust-NC-VMAT）和稳健 BROAD-RT 计划，在稳健优化期间，将三个轴向方向（左右、前后、上下）各 3 - 5 毫米的患者摆位不确定性应用于临床靶区（CTV）。高风险和低风险 CTV 的处方剂量分别为 70 Gy 和 56 Gy，分 35 次给予。比较各计划之间的剂量学参数，包括 CTV 的剂量覆盖和危及器官（OAR）的剂量 sparing。使用八种不确定性场景评估稳健性，每种场景通过在所有三个正交轴（左右、前后、上下）上同时应用±1.7 毫米的平移位移生成，导致组合矢量位移约为 3 毫米。
与稳健 VMAT 计划相比，稳健 BROAD-RT 计划使对侧和同侧腮腺以及口腔的平均剂量分别显著降低 8.17、6.20 和 3.03 Gy（分别为 p < 0.001、p < 0.001 和 p = 0.002）。同样，与稳健 NC-VMAT 计划相比，稳健 BROAD-RT 计划使腮腺和口腔的剂量显著更低（分别为 p = 0.004、p = 0.014 和 p = 0.014）。三种技术在靶区覆盖指数（D98、D50）、适形指数（CI）或均匀性指数（HI）方面未观察到显著差异。最坏情况分析表明，稳健 BROAD-RT、稳健 VMAT 和稳健 NC-VMAT 计划中这些靶区相关参数的恶化程度没有显著差异。
稳健 BROAD-RT 计划在保持与传统稳健 VMAT 计划相当的稳健性的同时，进一步降低了腮腺和口腔的剂量。
