Gorgisyan Jenny, Munck Af Rosenschold Per, Perrin Rosalind, Persson Gitte F, Josipovic Mirjana, Belosi Maria Francesca, Engelholm Svend Aage, Weber Damien C, Lomax Antony J
Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland; Department of Oncology, Rigshospitalet Copenhagen University Hospital, Copenhagen, Denmark; Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
Department of Oncology, Rigshospitalet Copenhagen University Hospital, Copenhagen, Denmark; Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
Int J Radiat Oncol Biol Phys. 2017 Dec 1;99(5):1121-1128. doi: 10.1016/j.ijrobp.2017.08.023. Epub 2017 Aug 24.
We evaluated the feasibility of treating patients with locally advanced non-small cell lung cancer (NSCLC) with pencil beam scanned intensity modulated proton therapy (IMPT) in breath-hold.
Fifteen NSCLC patients who had previously received 66 Gy in 33 fractions with image guided photon radiation therapy were included in the present simulation study. In addition to a planning breath-hold computed tomography (CT) scan before the treatment start, a median of 6 (range 3-9) breath-hold CT scans per patient were acquired prospectively throughout the radiation therapy course. Three-field IMPT plans were constructed using the planning breath-hold CT scan, and the four-dimensional dose distributions were simulated, with consideration of both patient intra- and interfraction motion, in addition to dynamic treatment delivery.
The median clinical target volume receiving 95% of the prescribed dose was 99.8% and 99.7% for the planned and simulated dose distributions, respectively. For 3 patients (20%), the dose degradation was >5%, and plan adjustment was needed. Dose degradation correlated significantly with the change in water-equivalent path lengths (P<.01) in terms of the percentage of voxels with 3-mm or more undershoot on repeat CT scans. The dose to the organs at risk was similar for the planned and simulated dose distributions. Three or fewer breath-holds per field would be required for 12 of the 15 patients, which was clinically feasible.
For 9 of 15 NSCLC patients, IMPT in breath-hold was both dosimetrically robust and feasible to deliver regarding the treatment time. Three patients would have required plan adaption to meet the dosimetric criteria. The change in water-equivalent path length is an indicator of plan robustness and should be considered for the selection of patients for whom the plan would require adaptation.
我们评估了采用笔形束扫描调强质子治疗（IMPT）在屏气状态下治疗局部晚期非小细胞肺癌（NSCLC）患者的可行性。
本模拟研究纳入了15例先前接受过图像引导光子放射治疗、33次分割给予66 Gy剂量的NSCLC患者。除了在治疗开始前进行一次计划屏气计算机断层扫描（CT）外，在整个放射治疗过程中，每位患者前瞻性地获取了中位数为6次（范围3 - 9次）的屏气CT扫描。使用计划屏气CT扫描构建三野IMPT计划，并模拟四维剂量分布，同时考虑患者的分次内和分次间运动以及动态治疗实施。
对于计划和模拟剂量分布，接受95%处方剂量的临床靶体积中位数分别为99.8%和99.7%。3例患者（20%）的剂量下降>5%，需要调整计划。就重复CT扫描上3毫米或更大剂量不足的体素百分比而言，剂量下降与水等效路径长度的变化显著相关（P<0.01）。计划和模拟剂量分布对危及器官的剂量相似。15例患者中有12例每个野所需屏气次数为3次或更少，这在临床上是可行的。
对于15例NSCLC患者中的9例，屏气状态下的IMPT在剂量学上是稳健的，并且在治疗时间方面是可行的。3例患者需要调整计划以满足剂量学标准。水等效路径长度的变化是计划稳健性的一个指标，在选择需要调整计划的患者时应予以考虑。
