Klassen Lukas Fabrizio, Hirashima Hideaki, Iramina Hiraku, Iwai Takahiro, Yoshimura Michio, Tanaka Hiroki, Mizowaki Takashi, Nakamura Mitsuhiro
Department of Advanced Medical Physics, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan; Department of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany.
Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan.
Phys Med. 2025 Jun;134:104991. doi: 10.1016/j.ejmp.2025.104991. Epub 2025 May 10.
We investigated whether an ultra-hypofractionated carbon-ion radiotherapy (CIRT) protocol for pancreatic cancer (PC) could produce satisfactory dosimetric results with or without cone-beam CT-guided adaptive replanning and explored the potential dosimetric advantages of the adapted protocol.
Eleven PC patients who underwent CBCT-guided online adaptive photon radiotherapy were selected. Data were imported into a CIRT treatment planning software to develop new plans for an ultra-hypofractionated CIRT protocol. Prescriptions and constraints were recalculated for a five-fraction schedule using a linear quadratic model for organs-at-risk (OARs) and targets, respectively. The biologically effective dose-equivalent prescribed dose was set at 43.2 Gy (relative biological effectiveness [RBE]). Each day, a synthetic CT (SCT) was generated from the planning CT (PCT) with the daily CBCT. A reference plan based on the PCT was compared to an adapted plan based on the SCT. Deformable image registration was used to allow summation of the daily doses.
The adapted plans met the clinical goals, whereas the reference plans exceeded the constraints in 27 % (stomach), 53 % (duodenum), and 31 % (small bowel) of the fractions. The adapted plans notably decreased V for all gastrointestinal OARs, while significantly enhancing the gross tumor volume (GTV) D and planning target volume (PTV) D. The accumulated doses showed significant improvements in the duodenum V, GTV D, and PTV D.
CBCT-guided adaptive CIRT for PC demonstrated favorable dosimetric results, notably enhancing the sparing of OARs and ensuring superior target coverage compared with non-adaptive CIRT protocols.
我们研究了一种用于胰腺癌（PC）的超分割碳离子放疗（CIRT）方案在有或没有锥束CT引导的自适应重新计划的情况下是否能产生令人满意的剂量学结果，并探讨了适应性方案潜在的剂量学优势。
选择11例接受CBCT引导的在线自适应光子放疗的PC患者。将数据导入CIRT治疗计划软件，以制定超分割CIRT方案的新计划。分别使用线性二次模型对危及器官（OARs）和靶区重新计算五分割方案的处方和约束条件。生物等效剂量规定剂量设定为43.2 Gy（相对生物效应[RBE]）。每天，从计划CT（PCT）和每日CBCT生成合成CT（SCT）。将基于PCT的参考计划与基于SCT的适应性计划进行比较。使用可变形图像配准来累加每日剂量。
适应性计划达到了临床目标，而参考计划在27%（胃）、53%（十二指肠）和31%（小肠）的分割中超出了约束条件。适应性计划显著降低了所有胃肠道OARs的V值，同时显著提高了大体肿瘤体积（GTV）的D值和计划靶体积（PTV）的D值。累积剂量在十二指肠V值、GTV D值和PTV D值方面有显著改善。
CBCT引导的PC适应性CIRT显示出良好的剂量学结果，与非适应性CIRT方案相比，显著提高了OARs的保护并确保了更好的靶区覆盖。
