Chen Deqi, Yang Xiongtao, Qin Shirui, Li Xiufen, Dai Jianrong, Tang Yuan, Men Kuo
Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China.
Department of Oncology, Beijing Changping Hospital, Beijing 102202, China.
Phys Imaging Radiat Oncol. 2025 Mar 3;33:100747. doi: 10.1016/j.phro.2025.100747. eCollection 2025 Jan.
Adaptive radiotherapy for patients with rectal cancer using a magnetic resonance-guided linear accelerator has limitations in managing bladder shape variations. Conventional couch shifts may result in missing the target while requiring a large margin. Conversely, fully adaptive strategy is time-consuming. Therefore, a more efficient strategy for online adaptive radiotherapy is required.
This retrospective study included 50 fractions from 10 patients with rectal cancer undergoing preoperative radiotherapy. The proposed method involved preparing a library of reference plans (LoRP) based on diverse bladder shapes. For each fraction, a plan from the LoRP was selected based on daily bladder filling. This plan was compared with those generated by conventional couch shift and fully adaptive strategies. The clinical acceptability of the plans (i.e., per protocol, variation-acceptable, or unacceptable) was assessed.
In per protocol criterion, 44 %, 6 %, and 100 % of the plans for LoRP, conventional couch shift, and fully adaptive strategies were achieved, respectively. In variation-acceptable criterion, 92 % of LoRP plans and 74 % of conventional couch shift plans were achieved. LoRP demonstrated 94 % target coverage (100 % prescription dose) in the fully adaptive strategy compared with 91 % in conventional couch shift strategy. The fully adaptive strategy had the best performance in sparing the intestine and colon. LoRP reduced the treatment session duration by more than a third (>20 min) compared with the fully adaptive strategy.
LoRP achieved adequate target coverage with a short treatment session duration, potentially increasing treatment efficiency and improving patient comfort.
使用磁共振引导直线加速器对直肠癌患者进行自适应放疗在处理膀胱形状变化方面存在局限性。传统的治疗床移位可能导致靶区遗漏，同时需要较大的安全边界。相反，完全自适应策略耗时较长。因此，需要一种更有效的在线自适应放疗策略。
这项回顾性研究纳入了10例接受术前放疗的直肠癌患者的50个分次。所提出的方法包括基于不同膀胱形状准备一个参考计划库（LoRP）。对于每个分次，根据每日膀胱充盈情况从LoRP中选择一个计划。将该计划与传统治疗床移位和完全自适应策略生成的计划进行比较。评估计划的临床可接受性（即符合方案、变异可接受或不可接受）。
在符合方案标准下，LoRP、传统治疗床移位和完全自适应策略的计划分别实现了44%、6%和100%。在变异可接受标准下，LoRP计划的92%和传统治疗床移位计划的74%得以实现。与传统治疗床移位策略的91%相比，LoRP在完全自适应策略中显示出94%的靶区覆盖（100%处方剂量）。完全自适应策略在保护小肠和结肠方面表现最佳。与完全自适应策略相比，LoRP将治疗疗程时长缩短了三分之一以上（>20分钟）。
LoRP在较短的治疗疗程时长内实现了足够的靶区覆盖，有可能提高治疗效率并改善患者舒适度。
