Analysis of organ motion management and dose optimization in deep inspiration breath hold radiotherapy for breast cancer
10.3760/cma.j.cn113030-20250512-00185
- VernacularTitle:乳腺癌深吸气屏气放疗的器官运动管理与剂量优化分析
- Author:
Hailei LIN
1
;
Hong GAO
1
;
Xiangyan SHA
1
;
Dan WANG
1
;
Rui WANG
1
;
Qinhong WU
1
;
Qiuzi ZHONG
1
;
Yonggang XU
1
;
Gaofeng LI
1
Author Information
1. 北京医院放疗科，国家老年医学中心，中国医学科学院老年医学研究院，北京 100730
- Publication Type:Journal Article
- Keywords:
Breast neoplasms;
Deep inspiration breath hold;
Intra-fraction error;
Gated window;
Radiation dose
- From:
Chinese Journal of Radiation Oncology
2025;34(12):1223-1229
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To compare the treatment time stability, inter- and intra-fraction errors, and clinical target volume (CTV) to planning target volume (PTV) margin expansions under different gated window settings in deep inspiration breath hold (DIBH) radiotherapy for breast cancer, and to analyze the correlation between organ at risk (OAR) dose optimization and changes in lung volume.Methods:A retrospective analysis was conducted on 65 patients with left-sided breast cancer who received DIBH radiotherapy after modified radical mastectomy. CT simulation positioning was performed using 2 mm or 3 mm gated window for DIBH, followed by target delineation, treatment planning, and dose verification. During treatment, setup errors guided by cone beam CT (CBCT), intra-fraction monitoring errors, and treatment times were recorded. The coefficient of variation (CV) of treatment time was calculated for both gated window settings. Based on inter- and intra-fraction error distributions, the expansion distance of the CTV were determined using the van Herk formula. Dosimetric differences between DIBH and free-breathing (FB) plans for the left lung, heart, and left anterior descending coronary artery (LAD) were compared. Spearman correlation analysis was performed between the relative increase in left lung volume and the relative reduction in OAR dose. Paired t-tests were used for inter-group comparisons. Results:The mean CV of the 3 mm gated window group was 0.08±0.03, which was lower than that of the 2 mm group (0.10±0.04; t=-3.91, P<0.001). The setup errors of the 2 mm group in the X, Y, and Z directions were (1.27±1.03), (1.68±0.94), (1.90±1.25) mm, respectively-significantly smaller than those of the 3 mm group [(1.81±1.41), (2.07±1.69), (2.93±1.90) mm; t=-5.80, -2.33, -5.33; P<0.001,=0.014,<0.001). Setup errors for both groups were within the 25%-75% range and all below 5 mm. The intra-fraction deviations of the 2 mm group in the X, Y, and Z directions were (0.54±0.33), (0.79±0.44), (0.70±0.53) mm, respectively, significantly smaller than those of the 3 mm group [(0.62±0.43), (0.93±0.66), (0.87±0.67) mm; t=-3.87, -3.46, -2.71,all P<0.001). The mean intra-fraction errors of both groups were within 1 mm, with greater deviations in the Y and Z directions than those in the X direction. The CTV expansion margins for the 2 mm group in the X, Y, and Z directions were 4.21, 5.35, 5.99 mm, respectively, while those for the 3 mm group were 5.81, 6.89, 9.06 mm. Compared with FB, DIBH significantly reduced the doses to the left lung, heart, and LAD (all P<0.01). The increase in left lung volume was moderately negatively correlated with the reduction in left lung D mean ( r=-0.43, P=0.028), and highly negatively correlated with the dose reductions to the heart and LAD (both P<0.001). Conclusions:The variability in respiratory gated window settings can lead to differences in treatment time stability as well as inter- and intra-fraction errors, consequently affecting CTV-to-PTV margins. The DIBH technique demonstrates significant dosimetric benefits in reducing radiation exposure to the left lung, heart, and LAD. Volumetric expansion of the left lung is strongly and inversely correlated with the reduction in radiation dose to both the heart and LAD.
