OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany.
Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
Radiat Oncol. 2017 Nov 28;12(1):190. doi: 10.1186/s13014-017-0931-8.
Proton beam therapy is promising for the treatment of head and neck cancer (HNC), but it is sensitive to uncertainties in patient positioning and particle range. Studies have shown that the planning target volume (PTV) concept may not be sufficient to ensure robustness of the target coverage. A few planning studies have considered irradiation of unilateral HNC targets with protons, but they have only taken into account the dose on the nominal plan, without considering anatomy changes occurring during the treatment course.
Four pencil beam scanning (PBS) proton therapy plans were calculated for 8 HNC patients with unilateral target volumes: single-field (SFO) and multi-field optimized (MFO) plans, either using the PTV concept or clinical target volume (CTV)-based robust optimization. The dose was recalculated on computed tomography (CT) scans acquired during the treatment course. Doses to target volumes and organs at risk (OARs) were compared for the nominal plans, cumulative doses considering anatomical changes, and additional setup and range errors in each fraction. If required, the treatment plan was adapted, and the dose was compared with the non-adapted plan.
All nominal plans fulfilled the clinical specifications for target coverage, but significantly higher doses on the ipsilateral parotid gland were found for both SFO approaches. MFO PTV-based plans had the lowest robustness against range and setup errors. During the treatment course, the influence of the anatomical variation on the dose has shown to be patient specific, mostly independent of the chosen planning approach. Nine plans in four patients required adaptation, which led to a significant improvement of the target coverage and a slight reduction in the OAR dose in comparison to the cumulative dose without adaptation.
The use of robust MFO optimization is recommended for ensuring plan robustness and reduced doses in the ipsilateral parotid gland. Anatomical changes occurring during the treatment course might degrade the target coverage and increase the dose in the OARs, independent of the chosen planning approach. For some patients, a plan adaptation may be required.
质子束疗法在治疗头颈部癌症（HNC）方面具有很大的前景，但对患者定位和粒子射程的不确定性很敏感。研究表明，计划靶区（PTV）概念可能不足以确保靶区覆盖的稳健性。一些规划研究已经考虑了用质子照射单侧 HNC 靶区，但它们只考虑了名义计划的剂量，而没有考虑治疗过程中发生的解剖结构变化。
为 8 名单侧靶区的 HNC 患者计算了 4 个铅笔束扫描（PBS）质子治疗计划：单野（SFO）和多野优化（MFO）计划，分别使用 PTV 概念或基于临床靶区（CTV）的稳健优化。在治疗过程中获取的计算机断层扫描（CT）扫描上重新计算剂量。比较了名义计划、考虑解剖变化的累积剂量以及每个分次的额外设置和射程误差的靶区和危及器官（OAR）剂量。如果需要，会调整治疗计划，并将剂量与未调整的计划进行比较。
所有名义计划都满足了靶区覆盖的临床要求，但对于两种 SFO 方法，同侧腮腺的剂量明显更高。MFO PTV 基于的计划对射程和设置误差的稳健性最低。在治疗过程中，解剖变异对剂量的影响显示出患者特异性，主要与所选规划方法无关。四名患者中有九份计划需要调整，与不调整累积剂量相比，这导致靶区覆盖的显著改善和 OAR 剂量的轻微降低。
推荐使用稳健的 MFO 优化来确保计划的稳健性和同侧腮腺的剂量降低。治疗过程中发生的解剖变化可能会降低靶区的覆盖范围，并增加 OAR 的剂量，而与所选的规划方法无关。对于一些患者，可能需要调整计划。
