2973 - Dosimetric Benefits with Anatomical Analysis of Deep Inspiration Breath-Hold Technique in Bilateral Breast Radiotherapy
Presenter(s)
J. Ma1, S. Jiao2, Y. Liang3, K. Ren4, K. Zhang1, J. Shen1, K. Zhao5, X. Meng3, Y. Liu6, B. Yang7, X. Hou8, K. Hu9, J. Qiu3, and F. Zhang10; 1Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, 2Peking Union Medical College Hospital, Beijing 100730, China, China, 3Department of Radiation Oncology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China, 4Department of Radiation Oncology, Peking Union Medical College Hospital, Chinese Academy of medical Sciences & Peking Union Medical College, Beijing 100730, China, China, 5Shanghai United Imaging Healthcare Company, Shanghai, China, 6Shenzhen United Imaging Research Institute of Innovative Medical Equipment, Shenzhen, China, 7Department of Radiation Oncology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, Beijing, China, 8Department of Radiation Oncology, Peking Union Medical College Hospital, Chinese Academy of medical Sciences & Peking Union Medical College, Beijing, China, 9Peking Union Medical College Hospital, Beijing, China, 10Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China
Purpose/Objective(s):
Deep inspiration breath-hold (DIBH) has been widely used after breast cancer conservation therapy to reduce the risk of late cardiotoxicity in radiotherapy for the left breast. However, its application in bilateral breast cancer is rarely reported. Our aim was to explore the dose-sparing benefits of DIBH in bilateral breast radiotherapy and investigate the relationship between anatomical structures and dosimetry variations.Materials/Methods: We simulated the contouring of clinical targets for bilateral breast cancer after breast-conserving surgery radiotherapy using free breathing (FB) and DIBH-positioned CT scans of 17 left breast cancer patients who received DIBH radiotherapy at one institution. Plan simulation was performed using volumetric modulated arc therapy. We compared the organs at risk doses between the FB and DIBH groups, correlated anatomical structures and dosimetry, and determined the super-linear dynamics between anatomical variations in DIBH and FB and their dosimetric impacts using a 3D dose prediction model.
Results: Comparing to the FB group, the DIBH group significantly reduced the Dmax of the heart (p<0.001), the Dmean of the LAD (12.84 Gy vs. 8.13 Gy, p<0.001), and the Dmax of the LAD (36.65 vs. 22.5 Gy, p<0.001). The Dmean and Dmax of the liver and D2cc of the esophagus in the DIBH group were also significantly lower (2.95 Gy vs. 5.85 Gy, p<0.001; 23.98 Gy vs. 37.54 Gy, p<0.001; 5.76 Gy vs. 6.86 Gy, p=0.14). The doses to double lungs were not significantly different between the two groups. Correlation analysis revealed a strong association between the dosimetric benefits of DIBH and the resultant anatomical changes. Notably, a 6.3% decrease in heart volume during DIBH was positively correlated with reduced Dmean of the heart and the Dmax of the LAD, with correlation coefficients of 0.70 and 0.68, respectively. An average increase of 5.68 mm in the minimum distance to the target volume for the LAD was inversely correlated with the Dmax of the heart and LAD, with coefficients of -0.63 and -0.72, respectively. Using a 3D dose prediction model, we identified super-linear relationships between anatomical structures and dose distribution. The predicted dose reductions for the Dmax of the heart, LAD, and liver in the DIBH plans exhibited high correlations with the actual dose reductions in the original plans, with correlation coefficients of 0.94, 0.98, and 0.91, respectively.
Conclusion: For patients with bilateral breast cancer after breast-conserving surgery, applying the DIBH technique can significantly reduce the doses to the heart, LAD, liver, and esophagus, which may help reduce the side effects of radiotherapy. The primary mechanism underpinning the dosimetric benefits of DIBH is the anatomical repositioning of critical structures. The strong correlations observed among various anatomical and dosimetric indicators underscore the pivotal role of these structural changes in conferring the dose-sparing effects of the DIBH technique.