Department of Radiation Oncology, Erasmus MC Cancer Institute, Rotterdam, The Netherlands.
Department of Radiation Oncology, Erasmus MC Cancer Institute, Rotterdam, The Netherlands.
Phys Med. 2022 Sep;101:20-27. doi: 10.1016/j.ejmp.2022.06.017. Epub 2022 Jul 16.
Complexity in selecting optimal non-coplanar beam setups and prolonged delivery times may hamper the use of non-coplanar treatments for nasopharyngeal carcinoma (NPC). Automated multi-criterial planning with integrated beam angle optimization was used to define non-coplanar VMAT class solutions (CSs), each consisting of a coplanar arc and additional 1 or 2 fixed, non-coplanar partial arcs.
Automated planning was used to generate a coplanar VMAT plan with 5 complementary computer-optimized non-coplanar IMRT beams (VMAT+5) for each of the 20 included patients. Subsequently, the frequency distribution of the 100 patient-specific non-coplanar IMRT beam directions was used to select non-coplanar arcs for supplementing coplanar VMAT. A second investigated CS with only one non-coplanar arc consisted of coplanar VMAT plus a partial arc at 90° couch angle (VMATCS90). Plans generated with the two VMATCSs were compared to coplanar VMAT.
VMAT+5 analysis resulted in VMATCS60: two partial non-coplanar arcs at couch angles 60° and -60° to complement coplanar VMAT. Compared to coplanar VMAT, the non-coplanar VMATCS60 and VMATCS90 yielded substantial average dose reductions in OARs associated with xerostomia and dysphagia, i.e., parotids, submandibular glands, oral cavity and swallowing muscles (p < 0.05) for the same PTV coverage and without violating hard constraints. Impact of non-coplanar treatment and superiority of either VMACS60 and VMATCS90 was highly patient dependent.
Compared to coplanar VMAT, dose to OARs was substantially reduced with a CS with one or two non-coplanar arcs. Preferences for coplanar or one or two additional arcs are highly patient-specific, balancing plan quality and treatment time.
选择最佳非共面射束设置的复杂性和延长的治疗时间可能会阻碍非共面治疗鼻咽癌（NPC）的应用。使用自动化多标准规划和集成射束角度优化来定义非共面 VMAT 类解决方案（CS），每个 CS 由一个共面弧和另外 1 个或 2 个固定的非共面部分弧组成。
为 20 名纳入的患者中的每一位患者，使用自动化规划生成一个具有 5 个互补的计算机优化的非共面调强放疗射束（VMAT+5）的共面 VMAT 计划。随后，使用 100 个患者特定的非共面调强放疗射束方向的频率分布来选择补充共面 VMAT 的非共面弧。第二个研究的 CS 仅包含一个非共面弧，由共面 VMAT 加 90°床角的部分弧组成（VMATCS90）。比较了这两种 VMATCS 生成的计划与共面 VMAT。
VMAT+5 分析得到了 VMATCS60：两个在床角为 60°和-60°的部分非共面弧来补充共面 VMAT。与共面 VMAT 相比，非共面 VMATCS60 和 VMATCS90 使与口干和吞咽困难相关的 OAR 平均剂量显著降低，即腮腺、颌下腺、口腔和吞咽肌肉（p<0.05），同时保持相同的 PTV 覆盖范围，且不违反硬约束。非共面治疗的影响和 VMATCS60 和 VMATCS90 中任何一个的优势高度依赖于患者。
与共面 VMAT 相比，使用一个或两个非共面弧的 CS 可使 OAR 剂量显著降低。对共面或一个或两个附加弧的偏好高度取决于患者，在计划质量和治疗时间之间取得平衡。
