QST Hospital, National Institutes for Quantum Science and Technology, Chiba, Japan;
Department of Accelerator and Medical Physics, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, Chiba, Japan.
Anticancer Res. 2024 Sep;44(9):3821-3828. doi: 10.21873/anticanres.17208.
BACKGROUND/AIM: Carbon-ion radiotherapy (CiRT) has been used for the treatment of locally advanced pancreatic cancer (LAPC) with uniform dose plan. The aim of the present study is to investigate the effectiveness of a simultaneous integrated boost (SIB) technique with scanned CiRT against LAPC.
Data of 21 patients with LAPC were used to compare two treatment planning approaches: a conventional uniform dose approach and a SIB approach. A relative biological effectiveness (RBE)-weighted dose (D) of 55.2 Gy (RBE) in 12 fractions was prescribed to the planning target volume (PTV) in the conventional approach. In the SIB approach, D of 67.2 Gy (RBE) and 43.2 Gy (RBE) in 12 fractions were prescribed to a high-risk PTV (HR-PTV) and low-risk PTV (LR-PTV), respectively. The D and dose-averaged linear energy transfer (LET) of targets and gastrointestinal tracts as organs at risk (OARs) were evaluated.
The HR-PTV D and LR-PTV D were 64.4±0.6 and 42.5±0.1 Gy (RBE) in SIB approach compared to the PTV D of 54.1±0.4 Gy (RBE) in the conventional approach. All SIB plans achieved the D lower than 46 Gy (RBE) and V lower than 4 cm within OARs. The SIB approach increased the minimum LET within the GTV to 44 keV/μm or higher for 20 out of 21 patients as compared to 16 out of 21 patients in the conventional approach.
The SIB approach effectively increased the RBE-weighted dose and LET within the HR-PTV and GTV by accumulating the high-LET stopping carbon-ions into the HR-PTV in addition to the decreased RBE-weighted dose to OARs.
背景/目的：碳离子放射疗法（CiRT）已用于局部晚期胰腺癌（LAPC）的治疗，采用统一剂量计划。本研究旨在研究扫描 CiRT 同步整合升压（SIB）技术治疗 LAPC 的效果。
使用 21 例 LAPC 患者的数据比较两种治疗计划方法：常规均匀剂量方法和 SIB 方法。在常规方法中，计划靶区（PTV）规定了 55.2 Gy（RBE）的相对生物有效剂量（D），12 个分次。在 SIB 方法中，高风险 PTV（HR-PTV）和低风险 PTV（LR-PTV）分别规定了 67.2 Gy（RBE）和 43.2 Gy（RBE）的 D。评估了靶区和胃肠道等危及器官（OARs）的 D 和剂量平均线性能量传递（LET）。
SIB 方法中 HR-PTV D 和 LR-PTV D 分别为 64.4±0.6 和 42.5±0.1 Gy（RBE），而常规方法中 PTV D 为 54.1±0.4 Gy（RBE）。所有 SIB 计划均使 OAR 内 D 低于 46 Gy（RBE）和 V 低于 4 cm。与常规方法相比，SIB 方法使 21 例患者中有 20 例 GTV 内的最小 LET 增加到 44 keV/μm 或更高，而常规方法中只有 16 例。
SIB 方法通过将高 LET 停止碳离子累积到 HR-PTV 中，除了降低 OAR 的 RBE 加权剂量外，还有效地增加了 HR-PTV 和 GTV 内的 RBE 加权剂量和 LET。
