Center for Proton Therapy, Paul Scherrer Institute , Villigen , Switzerland.
Department of Physics, ETH Zurich , Zurich , Switzerland.
Acta Oncol. 2019 Oct;58(10):1423-1428. doi: 10.1080/0284186X.2019.1641217. Epub 2019 Jul 31.
For proton therapy of paranasal tumors, field directions avoiding volumes that might change during therapy are typically used. If the plan is optimized on the daily anatomy using daily adapted proton therapy (DAPT) however, field directions crossing the nasal cavities might be feasible. In this study, we investigated the effectiveness of DAPT for enabling narrow-field treatment approaches. For five paranasal tumor patients, representing a wide patient spectrum, anatomically robust 4-field-star and narrow-field plans were calculated and their robustness to anatomical and setup uncertainties was compared with and without DAPT. Based on the nominal planning CTs, per patient up to 125 simulated CTs (simCTs) with different nasal cavity fillings were created and random translations and rotations due to patient setup uncertainties were further simulated. Plans were recalculated or re-optimized on all error scenarios, representing non-adapted and DAPT fractions, respectively. From these, 100 possible treatments (60 GyRBE, 30 fx) were simulated and changes in integral dose, target and organs at risk (OARs) doses evaluated. In comparison to the 4-field-star approach, the use of narrow-fields reduced integral dose between 29% and 56%. If OARs did not overlap with the target, OAR doses were also reduced. Finally, the significantly reduced target coverage in non-adapted treatments (mean V95 reductions of up to 34%) could be almost fully restored with DAPT in all cases (differences <1%). DAPT was found to be not only an effective way to increase plan robustness to anatomical and positional uncertainties, but also opened the possibility to use improved and more conformal field arrangements.
对于鼻窦肿瘤的质子治疗，通常使用避开治疗过程中可能发生变化的体积的射野方向。然而，如果使用每日自适应质子治疗（DAPT）在每日解剖结构上优化计划，那么穿过鼻腔的射野方向可能是可行的。在这项研究中，我们研究了 DAPT 实现窄野治疗方法的有效性。对于五个代表广泛患者谱的鼻窦肿瘤患者，计算了具有解剖结构稳健性的 4 野星野和窄野计划，并比较了在有和没有 DAPT 的情况下，这些计划对解剖结构和设置不确定性的稳健性。基于名义计划 CT，为每位患者创建了多达 125 个具有不同鼻腔填充的模拟 CT（simCT），并进一步模拟了由于患者设置不确定性导致的随机平移和旋转。分别在没有适应和 DAPT 部分的所有误差场景下重新计算或重新优化计划。从这些计划中，模拟了 100 种可能的治疗（60 GyRBE，30 fx），并评估了整体剂量、靶区和危及器官（OARs）剂量的变化。与 4 野星野方法相比，使用窄野将整体剂量降低了 29%至 56%。如果 OARs 不与靶区重叠，则 OARs 剂量也会降低。最后，在没有适应的治疗中，靶区覆盖率明显降低（最大 V95 降低高达 34%），但在所有情况下，DAPT 几乎可以完全恢复（差异<1%）。DAPT 不仅是增加计划对解剖结构和位置不确定性的稳健性的有效方法，而且还为使用改进的、更符合适形的射野排列提供了可能性。
