Institute of Modern Physics, Fudan University, Shanghai, China.
Department of Radiation Oncology, Shanghai Chest Hospital, Shanghai Jiaotong University, Shanghai, China.
Radiat Oncol. 2021 Jun 27;16(1):119. doi: 10.1186/s13014-021-01848-9.
BACKGROUND/PURPOSE: To establish regression models of physical and equivalent dose in 2 Gy per fraction (EQD) plan parameters of two kinds of hybrid planning for stage III NSCLC.
Two kinds of hybrid plans named conventional fraction radiotherapy & stereotactic body radiotherapy (C&S) and conventional fraction radiotherapy & simultaneous integrated boost (C&SIB) were retrospectively made for 20 patients with stage III NSCLC. Prescription dose of C&S plans was 2 Gy × 30f for planning target volume of lymph node (PTV) and 12.5 Gy × 4f for planning target volume of primary tumor (PTV), while prescription dose of C&SIB plans was 2 Gy × 26f for PTV and sequential 2 Gy × 4f for PTV combined with 12.5 Gy × 4f for PTV. Regression models of physical and EQD plan parameters were established based on anatomical geometry features for two kinds of hybrid plans. The features were mainly characterized by volume ratio, min distance and overlapping slices thickness of two structures. The possibilities of regression models of EQD plan parameters were verified by spearman's correlation coefficients between physical and EQD plan parameters, and the influence on the consistence of fitting goodness between physical and EQD models was investigated by the correlations between physical and EQD plan parameters. Finally, physical and EQD models predictions were compared with plan parameters for two new patients.
Physical and EQD plan parameters of PTV CI have shown strong positive correlations with PTV volume and min distance, and strong negative correlations with PTV volume for two kinds of hybrid plans. PTV CI is not only correlated with above three geometry features, but also negatively correlated with overlapping slices thickness. When neck lymph node metastasis was excluded from PTV volume, physical and EQD total lung V showed a high linear correlation with corrected volume ratio Meanwhile, physical total lung mean dose (MLD) had a high linear correlation with corrected volume ratio, while EQD total lung MLD was not only affected by corrected volume ratio but also volume ratio Heart D, D and mean dose (MHD) would be more susceptible to overlapping structure. Min distance may be an important feature for predicting EQD esophageal max dose for hybrid plans. It's feasible for regression models of EQD plan parameters, and the consistence of the fitting goodness of physical and EQD models had a positive correlation with spearman's correlation coefficients between physical and EQD plan parameters. For total lung V, ipsilateral lung V, and ipsilateral lung MLD, the models could predict that C&SIB plans were higher than C&S plans for two new patients.
The regression models of physical and EQD plan parameters were established with at least moderate fitting goodness in this work, and the models have a potential to predict physical and EQD plan parameters for two kinds of hybrid planning.
背景/目的：为了建立两种 III 期 NSCLC 混合计划的 2Gy 分次（EQD）计划参数的物理和等效剂量的回归模型。
回顾性地为 20 例 III 期 NSCLC 患者制作了两种混合计划，分别为常规分次放疗与立体定向体部放疗（C&S）和常规分次放疗与同期加量放疗（C&SIB）。C&S 计划的处方剂量为淋巴结计划靶区（PTV）的 2Gy×30f 和原发肿瘤计划靶区（PTV）的 12.5Gy×4f，而 C&SIB 计划的处方剂量为 PTV 的 2Gy×26f 和 PTV 联合 12.5Gy×4f 的序贯 2Gy×4f。基于两种混合计划的解剖几何特征，建立了物理和 EQD 计划参数的回归模型。这些特征主要由两个结构的体积比、最小距离和重叠切片厚度来描述。通过物理和 EQD 计划参数之间的 Spearman 相关系数验证了 EQD 计划参数回归模型的可能性，并通过物理和 EQD 计划参数之间的相关性研究了对物理和 EQD 模型拟合优度一致性的影响。最后，将物理和 EQD 模型的预测值与两个新患者的计划参数进行了比较。
两种混合计划的 PTV CI 的物理和 EQD 计划参数与 PTV 体积和最小距离呈强正相关，与 PTV 体积呈强负相关。PTV CI 不仅与上述三个几何特征相关，还与重叠切片厚度呈负相关。当排除颈部淋巴结转移时，物理和 EQD 全肺 V 与校正体积比呈高度线性相关。同时，物理全肺平均剂量（MLD）与校正体积比呈高度线性相关，而 EQD 全肺 MLD 不仅受校正体积比影响，还受体积比心脏 D、D 和平均剂量（MHD）的影响。重叠结构更敏感。最小距离可能是预测混合计划 EQD 食管最大剂量的一个重要特征。EQD 计划参数的回归模型是可行的，物理和 EQD 计划参数之间的 Spearman 相关系数与物理和 EQD 模型拟合优度的一致性呈正相关。对于全肺 V、同侧肺 V 和同侧肺 MLD，模型可以预测对于两个新患者，C&SIB 计划高于 C&S 计划。
本研究中建立了至少具有中等拟合优度的物理和 EQD 计划参数回归模型，该模型有望预测两种混合计划的物理和 EQD 计划参数。
