Selection of radiotherapy plans with different arc angles for left-sided breast cancer based on anatomical structures
10.3760/cma.j.cn112271-20250625-00214
- VernacularTitle:解剖结构对左侧乳腺癌根治术后不同拉弧角度放疗计划选择研究
- Author:
Zhipeng ZHU
1
;
Maoying LAN
;
Xue OU
;
Guihua LI
;
Lianrong ZHENG
Author Information
1. 广西医科大学第二附属医院放疗科，南宁 530000
- Publication Type:Journal Article
- Keywords:
Deep inspiration breast hold (DIBH);
Anatomical structure;
Left-sided breast cancer;
Arc
- From:
Chinese Journal of Radiological Medicine and Protection
2025;45(9):884-891
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To compare four postmastectomy radiotherapy plans with different arc angles for left-sided breast cancer prepared using deep inspiration breath hold (DIBH) technique, in order to explore the feasibility of selecting optimal arc angles based on the parameters of patients′ anatomical structures.Methods:A total of 51 patients who underwent postmastectomy radiotherapy for left-sided breast cancer using DIBH at the Second Affiliated Hospital of Guangxi Medical University and the First Affiliated Hospital of Guangzhou Medical University were selected. Among these, 40 patients selected using simple random sampling were treated with four radiotherapy plans with different arc angles, labeled as SV120, SV100, SV80, and SV60, while the remaining 11 patients were treated with only the SV60 plans. The dose parameters of the target volumes (TVs) and organs at risk (the heart, lungs, and contralateral breast), as well as the beam-on times of individual arcs, in these plans were compared. The parameters of the anatomical structures (i.e., the heart, lung, and breast) of the 51 patients, including PHeart, PLungl, and PBreast, were extracted. Taking these parameters as independent variables and the quality of the SV60 plans as the dependent variable, fitting was conducted using P(SV60)—a multivariate logistic regression model—based on a training set (45 patients) and a testing set (six patients). The classification threshold of the plans was set at 0.5. Results:As the arc angle increased, the plans exhibited improved modulation capabilities for TVs and the left lung. However, the V5 of the right lung and the average beam-on time of a single arc also increased. The SV120 plans demonstrated significantly better V107% of planning target volume (PTV; 6.84%), homogeneity index (HI; 0.13), conformity index (CI; 0.81), and mean dose to the left lung (1 330.97 cGy) compared to the other three types of plans, with statistically significant differences ( W = 0-99, P < 0.001). The SV60 plans displayed lower mean doses to the contralateral breast (198.97 cGy) and the heart (440.35 cGy) and lower V5 of the right lung (0.27%) than the other three types of plans, with significant differences in V5 of the right lung and the mean dose to the contralateral breast ( W = 0-157, P < 0.001). In contrast, no significant difference was observed in these parameters (except for V5 of the right lung) among the other three types of plans. The four types of plans exhibited average beam-on times of individual arcs of 22.0, 19.1, 16.1, and 14.4 s, respectively, with statistically significant differences ( χ2= 93.0, P < 0.001). A multivariate logistic regression model revealed that PLungl, PHeart, and PBreast were negatively correlated with the quality of the SV60 plans ( t = -64.84, -28.20, -24.45, P<0.001). This model yielded an accuracy of 93.33% and a precision of 92.86% in the training set, while its accuracy and precision reached 100% in the testing set. Conclusions:For patients treated with postmastectomy radiotherapy for left-sided breast cancer using DIBH, it is feasible to select appropriate arc angles based on patients’ anatomical structures.
