Adaptation demand in proton beam therapy for head and neck tumour patients

在头颈癌的分割放射治疗过程中，患者的解剖结构往往会发生相当大的变化。由于质子射程会受到组织变化的强烈影响，因此，在没有规律的伴随成像和合理的治疗计划适应的情况下进行质子治疗(PT)似乎是HNC患者的关键。在能够建立适当的适应策略之前，需要估计在标准分割PT期间对治疗计划适应的实际需求。由于仅对常规光子治疗进行了全面的调查，仍然不确定(1)头颈部的逐渐解剖变化如何影响物理质子剂量分布，(2)考虑到整个治疗过程中的实际输送剂量，可以预期哪些生物学后果，以及(3)对于必要的计划适应是否有指示器或甚至特定的时间间隔。因此，产生了以下目标：室内计算机断层扫描图像(CT)的数据池，从HNC患者的放射治疗过程中收集的，需要在整个项目期间进行组装。强度调制PT的治疗计划将在初始的临床勾画的CT图像上创建。解剖学变化及其对非适应PT期间潜在剂量降解的影响将被量化。这些分析将考虑单个分数剂量以及总剂量分布，包括它们在估计的肿瘤控制和毒性概率方面的生物学评估。在这些调查的基础上，应推导出适当的时间点和潜在的一般和/或患者特定的治疗计划指标。预期的工作将通过使用治疗计划平台RayStation(瑞典斯德哥尔摩RaySearch实验室AB)在计算机研究中实现。将特别强调基于脚本的自动化，以使耗时的例行过程更快、更不容易出错。这些脚本也将被要求减少可行的适应PT的时间和精力，这将在未来的研究中被考虑。关于PT中HNC患者的适应需求的分析结果将成为进一步研究的基础，例如，所需的对照CT的数量或强大的治疗计划的必要性和优势。此外，它们是在德累斯顿大学发展适应性PT的可行概念的先决条件。

Considerable changes in patient's anatomy occur often during the course of fractionated radiotherapy of head-and-neck cancer (HNC). Since the range of proton beams can be strongly affected by tissue changes, the delivery of proton therapy (PT) without regular accompanying imaging and reasonable treatment plan adaptation seems to be critical for HNC patients. Before being able to establish appropriate adaptation strategies, the actual demand for treatment plan adaptation during standard-fractionated PT needs to be estimated.Since comprehensive investigations have been mainly performed for conventional photon therapy only, it is still uncertain(1) how the gradual anatomical changes in the head-and-neck region may affect the physical proton dose distribution,(2) which biological consequences can be expected considering the actually delivered dose during the whole treatment course and(3) whether there are indicators or even certain time intervals for a necessary plan adaptation.Consequently, the following objectives arise:A data pool of in-room computed tomography images (CTs), gathered from HNC patients during their radiotherapy treatment course, needs to be assembled throughout the project period. Treatment plans for intensity-modulated PT will be created on the initial, clinically delineated CT images. Anatomical changes and their impact on potential dose degradations during non-adapted PT will be quantified. These analyses will consider single fraction doses as well as the total dose distributions including their biological assessment in terms of estimated tumour control and toxicity probabilities. Based on these investigations, appropriate time points and potential general and/or patient-specific indicators for treatment plan adaptation shall be deduced.The envisaged work will be realized as in silico study using the treatment planning platform RayStation (RaySearch Laboratories AB, Stockholm Sweden). Particular emphasis will be placed on a script-bases automation to make time-consuming routine processes faster and less error-prone. Such scripts will also be required to reduce the time and effort of a practicable adapted PT which will be considered within future studies.The results of the analyses regarding the adaptation demand for HNC patients in PT will be the basis for further investigations concerning e.g. the amount of required control CTs or the necessity and advantage of robust treatment plans. Moreover, they are a prerequisite for the development of practicable concepts for adaptive PT at the UniversitätsProtonenTherapieDresden.