Technical Note: Treatment planning system (TPS) approximations matter - comparing intensity-modulated proton therapy (IMPT) plan quality and robustness between a commercial and an in-house developed TPS for nonsmall cell lung cancer (NSCLC)
Technical Note: Treatment planning system (TPS) approximations matter - comparing intensity-modulated proton therapy (IMPT) plan quality and robustness between a commercial and an in-house developed TPS for nonsmall cell lung cancer (NSCLC)
复制标题
DOI：
10.1002/mp.13809
复制
发表时间：
2019-09-21
期刊：
影响因子：
3.8
通讯作者：
Liu, Wei
中科院分区：
文献类型：
--
作者：
Liu, Chenbin;Yu, Nathan Y.;Liu, Wei
目的采用近似剂量计算方法，对商业化质子治疗计划系统（CTPS）中的标称剂量分布和不确定性引起的扰动剂量分布进行优化，以实现调强质子治疗（IMPT）的稳健优化。我们的目的是调查是否近似影响计划的质量，鲁棒性，并产生IMPT计划治疗局部晚期肺癌患者的相互作用的影响。材料与方法选择10例连续治疗的局部晚期非小细胞肺癌（NSCLC）患者。分别使用我们内部开发的TPS（名为“Solo”）和CTPS Eclipse（TM）（Varian Medical Systems，Palo Alto，CA，USA）为每位患者创建两个IMPT计划。这些计划旨在将处方剂量输送到医生在平均四维计算机断层扫描（4D-CT）上绘制的内部靶体积（ITV）。将单独计划导入CTPS，并在CTPS中重新计算以进行公平比较。通过重新计算吸气和呼气阶段的剂量，对每例患者的两个计划进行进一步验证，以确保所有计划均符合临床要求。在最坏情况下，使用剂量体积直方图（DVH）指数对所有阶段的计划稳健性进行量化。使用内部开发的软件评价每个计划的相互作用效应，该软件基于患者的呼吸运动模式和以时间依赖性方式的质子点输送，将每个部分的每个射野的起始阶段和呼气阶段的累积剂量随机化。采用Wilcoxon秩和检验比较DVH指数。结果Solo计划的靶区剂量覆盖率和均匀性明显优于CTPS计划（按处方剂量标准化）在最差情况下[ITV D-95%：98.04% vs 96.28%，Solo vs CTPS，P = 0.020; ITV D-5%-D-95%：7.20% vs 9.03%，P = 0.049]，而所有DVH指数在标称情景下均相当。在吸入阶段，Solo计划在标称情况下具有更好的目标剂量覆盖范围和脐带D-max [ITV D-95%：99.36% vs 98.45%，Solo vs CTPS，P = 0.014;脐带D-max：20.07 vs 23.71戈伊（RBE），P = 0.027]，在最差情况下具有更好的目标覆盖范围和脐带D-max [ITV D-95%：97.89% vs 96.47%，Solo vs CTPS，P = 0.037;脊髓D最大值：24.57 vs 28.14戈伊（RBE），P = 0.037]。在呼气阶段，在标称场景[ITV D-95%：99.63% vs 98.87%，Solo vs CTPS，P = 0.037; cord D-max：19.67 vs 23.66戈伊（RBE），P = 0.039]和最差情况场景[ITV D-95%：98.20% vs 96.74%，Solo vs CTPS，P = 0.027;脊髓D-max：23.47 vs 27.93戈伊（RBE），P = 0.027]。在相互作用效应方面，Solo生成的计划具有显著更好的靶剂量覆盖率和均匀性，热点较少，食管D均值和脊髓D最大值较低[ITV D-95%：101.81% vs 98.68%，Solo vs CTPS，P = 0.002; ITV D-5%-D-95%：2.94% vs 7.51%，P = 0.002;脊髓D最大值：18.87 vs 22.29戈伊（RBE），P = 0.014]。结论与CTPS相比，Solo生成的IMPT计划提供了更好的脊髓保留，在所有考虑的阶段中具有更好的靶稳健性，并减少了相互作用。因此，目前商业TPS程序中使用的近似方法在为局部晚期肺癌患者病例生成最佳IMPT计划方面可能有改进的空间。
Purpose Approximate dose calculation methods were used in the nominal dose distribution and the perturbed dose distributions due to uncertainties in a commercial treatment planning system (CTPS) for robust optimization in intensity-modulated proton therapy (IMPT). We aimed to investigate whether the approximations influence plan quality, robustness, and interplay effect of the resulting IMPT plans for the treatment of locally advanced lung cancer patients. Materials and methods Ten consecutively treated locally advanced nonsmall cell lung cancer (NSCLC) patients were selected. Two IMPT plans were created for each patient using our in-house developed TPS, named "Solo," and also the CTPS, Eclipse(TM) (Varian Medical Systems, Palo Alto, CA, USA), respectively. The plans were designed to deliver prescription doses to internal target volumes (ITV) drawn by a physician on averaged four-dimensional computed tomography (4D-CT). Solo plans were imported back to CTPS, and recalculated in CTPS for fair comparison. Both plans were further verified for each patient by recalculating doses in the inhalation and exhalation phases to ensure that all plans met clinical requirements. Plan robustness was quantified on all phases using dose-volume-histograms (DVH) indices in the worst-case scenario. The interplay effect was evaluated for every plan using an in-house developed software, which randomized starting phases of each field per fraction and accumulated dose in the exhalation phase based on the patient's breathing motion pattern and the proton spot delivery in a time-dependent fashion. DVH indices were compared using Wilcoxon rank-sum test. Results Compared to the plans generated using CTPS on the averaged CT, Solo plans had significantly better target dose coverage and homogeneity (normalized by the prescription dose) in the worst-case scenario [ITV D-95%: 98.04% vs 96.28%, Solo vs CTPS, P = 0.020; ITV D-5%-D-95%: 7.20% vs 9.03%, P = 0.049] while all DVH indices were comparable in the nominal scenario. On the inhalation phase, Solo plans had better target dose coverage and cord D-max in the nominal scenario [ITV D-95%: 99.36% vs 98.45%, Solo vs CTPS, P = 0.014; cord D-max: 20.07 vs 23.71 Gy(RBE), P = 0.027] with better target coverage and cord D-max in the worst-case scenario [ITV D-95%: 97.89% vs 96.47%, Solo vs CTPS, P = 0.037; cord D-max: 24.57 vs 28.14 Gy(RBE), P = 0.037]. On the exhalation phase, similar phenomena were observed in the nominal scenario [ITV D-95%: 99.63% vs 98.87%, Solo vs CTPS, P = 0.037; cord D-max: 19.67 vs 23.66 Gy(RBE), P = 0.039] and in the worst-case scenario [ITV D-95%: 98.20% vs 96.74%, Solo vs CTPS, P = 0.027; cord D-max: 23.47 vs 27.93 Gy(RBE), P = 0.027]. In terms of interplay effect, plans generated by Solo had significantly better target dose coverage and homogeneity, less hot spots, and lower esophageal D-mean, and cord D-max [ITV D-95%: 101.81% vs 98.68%, Solo vs CTPS, P = 0.002; ITV D-5%-D-95%: 2.94% vs 7.51%, P = 0.002; cord D-max: 18.87 vs 22.29 Gy(RBE), P = 0.014].Conclusions Solo-generated IMPT plans provide improved cord sparing, better target robustness in all considered phases, and reduced interplay effect compared with CTPS. Consequently, the approximation methods currently used in commercial TPS programs may have space for improvement in generating optimal IMPT plans for patient cases with locally advanced lung cancer.