Aims

So far, the impact of intra-thoracic anatomical changes (ITACs) on patients treated with stereotactic ablative radiotherapy (SABR) for early-stage non-small cell lung cancer is unknown. Studying these is important, as ITACs have the potential to impact the workflow and reduce treatment quality. The aim of this study was to assess and categorise ITACs, as detected on cone beam computed tomography scans (CBCT), and their subsequent impact upon treatment in lung cancer patients treated with SABR.

Materials and methods

CBCTs from 100 patients treated with SABR for early non-small cell lung cancer were retrospectively reviewed. The presence of the following ITACs was assessed: atelectasis, infiltrative change, pleural effusion, baseline shift and gross tumour volume (GTV) increase and decrease. ITACs were graded using a traffic light protocol. This was adapted from a tool previously developed to assesses potential target undercoverage or organ at risk overdose. The frequency of physics or clinician review was noted. A linear mixed effects model was used to assess the relationship between ITAC grade and set-up time (time from first CBCT to beam delivery).

Results

ITACs were observed in 22% of patients. Twenty-one per cent of these were categorised as ‘red’, implying a risk of underdosage to the GTV. Most were ‘yellow’ (51%), indicating little impact upon planning target volume coverage of the GTV. Physics or clinician review was required in 10% of all treatment fractions overall. Three patients needed their treatment replanned. The mixed effect model analysis showed that ITACs cause a significant prolongation of set-up time (Χ²(3) = 9.22, P = 0.02).

Conclusion

Most ITACs were minor, but associated with unplanned physics or clinician review, representing a potentially significant resource burden. ITACs also had a significant impact upon set-up time, with consequences for the wider workflow and intra-fraction motion. Detailed guidance on the management of ITACs is needed to provide support for therapeutic radiographers delivering lung SABR.

中文翻译：

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胸腔内解剖变化对肺部立体定向消融放射治疗的影响

 目标

迄今为止，胸腔内解剖变化（ITAC）对接受立体定向消融放疗（SABR）治疗早期非小细胞肺癌患者的影响尚不清楚。研究这些很重要，因为 ITAC 有可能影响工作流程并降低治疗质量。本研究的目的是对锥形束计算机断层扫描 (CBCT) 检测到的 ITAC 进行评估和分类，以及它们对接受 SABR 治疗的肺癌患者的后续治疗影响。

 材料和方法

回顾性审查了 100 名接受 SABR 治疗的早期非小细胞肺癌患者的 CBCT。评估以下 ITAC 的存在：肺不张、浸润性改变、胸腔积液、基线偏移和总肿瘤体积 (GTV) 增加和减少。 ITAC 使用交通灯协议进行分级。这是根据先前开发的工具改编的，用于评估潜在目标覆盖不足或器官过量风险。记录了物理或临床医生审查的频率。使用线性混合效应模型来评估 ITAC 等级和设置时间（从第一次 CBCT 到光束传输的时间）之间的关系。

 结果

22% 的患者观察到 ITAC。其中 21% 被归类为“红色”，这意味着 GTV 存在剂量不足的风险。大多数是“黄色”（51%），表明对 GTV 的规划目标量覆盖影响不大。总共 10% 的治疗部分需要物理或临床医生审查。三名患者需要重新计划治疗。混合效应模型分析表明，ITAC 导致设置时间显着延长（ Χ ² (3) = 9.22， P = 0.02）。

 结论

大多数 ITAC 都很小，但与计划外的物理或临床医生审查相关，代表着潜在的重大资源负担。 ITAC 还对设置时间产生重大影响，从而影响更广泛的工作流程和分数内运动。需要关于 ITAC 管理的详细指导，为实施肺 SABR 的治疗放射技师提供支持。