Department of Radiotherapy, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, the Netherlands.
Department of Radiation Oncology, Leiden University Medical Center, Leiden, the Netherlands.
Radiother Oncol. 2024 Sep;198:110388. doi: 10.1016/j.radonc.2024.110388. Epub 2024 Jun 17.
In intensity-modulated proton therapy (IMPT), Bragg peaks result in steep distal dose fall-offs, while the lateral IMPT dose fall-off is often less steep than in photon therapy. High-energy pristine transmission ('shoot through') pencil beams have no Bragg peak in the patient, but show a sharp lateral penumbra at the target level. We investigated whether combining Bragg peaks with Transmission pencil beams ('IMPT&TPB') could improve head-and-neck plans by exploiting the steep lateral dose fall-off of transmission pencil beams.
Our system for automated multi-criteria IMPT plan optimisation was extended for combined optimisation of BPs and TPBs. The system generates for each patient a Pareto-optimal plan using a generic 'wish-list' with prioritised planning objectives and hard constraints. For eight nasopharynx cancer patients (NPC) and eight oropharynx cancer (OPC) patients, the IMPT&TPB plan was compared to the competing conventional IMPT plan with only Bragg peaks, which was generated with the same optimiser, but without transmission pencil beams.
Clinical OAR and target constraints were met in all plans. By allowing transmission pencil beams in the optimisation, on average 14 of the 25 investigated OAR plan parameters significantly improved for NPC, and 9 of the 17 for OPC, while only one OPC parameter showed small but significant deterioration. Non-significant differences were found in the remaining parameters. In NPC, cochlea D reduced by up to 17.5 Gy and optic nerve D by up to 11.1 Gy.
Compared to IMPT, IMPT&TPB resulted in comparable target coverage with overall superior OAR sparing, the latter originating from steeper dose fall-offs close to OARs.
在调强质子治疗（IMPT）中，布拉格峰导致陡峭的远端剂量下降，而侧向 IMPT 剂量下降通常不如光子治疗陡峭。高能原始传输（“穿透”）铅笔束在患者体内没有布拉格峰，但在靶区水平显示出明显的锐利侧向半影。我们研究了是否可以通过利用传输铅笔束陡峭的侧向剂量下降来结合布拉格峰与传输铅笔束（“IMPT&TPB”）来改善头颈部计划。
我们用于自动多标准 IMPT 计划优化的系统扩展为 BP 和 TPB 的联合优化。该系统使用具有优先级规划目标和硬约束的通用“愿望清单”为每个患者生成 Pareto 最优计划。对于 8 例鼻咽癌（NPC）和 8 例口咽癌（OPC）患者，将 IMPT&TPB 计划与仅使用布拉格峰的竞争常规 IMPT 计划进行比较，该计划使用相同的优化器生成，但没有传输铅笔束。
所有计划均满足临床 OAR 和靶区限制。通过允许在优化中使用传输铅笔束，平均有 25 个研究的 OAR 计划参数中的 14 个对于 NPC 显著改善，17 个中的 9 个对于 OPC 显著改善，而只有一个 OPC 参数显示出较小但显著的恶化。其余参数无显著差异。在 NPC 中，耳蜗 D 减少了高达 17.5Gy，视神经 D 减少了高达 11.1Gy。
与 IMPT 相比，IMPT&TPB 导致可比的靶区覆盖，同时总体上更好地保护 OAR，后者源自靠近 OAR 的陡峭剂量下降。
