3007 - Radiation Esophagitis in Breast Cancer Patients Undergoing Hypofractionated Regional Nodal Radiotherapy: Voxel-Based Analysis
Presenter(s)
D. Q. Wang1, S. Yuan1, H. Jing2, H. Fang2, Y. W. Song2, Y. Liu2, J. Jin3, S. Qi2, Y. Tang4, N. Lu1, B. Chen2, N. Li5, Y. Zhai2, W. Zhang2, X. Liu2, G. Sun2, X. Zhao1, Y. X. Li2, T. Yu1, J. Dai1, and S. Wang2; 1Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, 2State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, National Cancer Center/ National Clinical Research Center for Cancer/ Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, 31State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing, China, 4Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing, China, 5State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing, China
Purpose/Objective(s): Voxel-based analysis (VBA) allows the full, 3-dimensional, dose distribution to be considered in radiotherapy outcome analysis. This study used VBA to investigate the spatial dose distribution difference in the esophagus between patients with and without = grade 2 radiation esophagitis (RE) in breast cancer, aiming to identify high-risk regions in the esophagus to predict RE and optimize the esophagus contouring.
Materials/Methods: 207 patients, treated between February 5, 2024 and May 8, 2020 and with minimum follow-up >6 months after radiotherapy, were prospectively included. All patients underwent photon radiotherapy to the chest wall, supraclavicular/infraclavicular fossa, level II axilla, and/or internal mammary chain with the prescribed dose of 43.5Gy in 15 fractions delivered with IMRT or VMAT techniques. RE was assessed weekly during RT, 1 week and 2 weeks after RT, as well as at 3 months and 6 months, and graded by the Common Toxicity Criteria for Adverse Events v3.0. There different lengths of esophagus were contoured, from the lower edge of the cricoid cartilage to the lower margin of the aortic arch as Eso1, to the lower edge of the tracheal prominence as Eso2, and to the gastroesophageal junction as Eso3. VBA was performed to identify the significant spatial dose distribution difference in the esophagus between patients with and without = grade 2 RE. The median volume image of the esophagus was selected as the common coordinate system (CCS). Images were registered to the CCS using a hybrid elastic image registration algorithm for global and region of interest implemented in commercially available software. The dose distribution was then propagated to the CCS for spatial normalization. For dose values within the esophagus, spatial dose-response patterns were analyzed using generalized linear models (GLM), and significance p-maps were generated. The False Discovery Rate (FDR) method was applied to adjust for multiple comparisons and control for type I error.
Results: Grade 2 and 3 RE incidence was 30.9% (64/207) and 0.5% (1/207), respectively. No grade 4 or 5 RE was observed.97 (46.9%) patients had left-sided tumors, and 110 (53.1%) had right-sided tumors. The VBA was performed in Eso1, Eso2 and Eso3 to identify p-maps of significant spatial dose distribution difference in the esophagus (high-risk regions) between patients with and without = grade 2 RE. The relationship of high-risk regions with different esophagus contourings showed that the high-risk regions were all located within Eso1, suggesting that Eso1 is an optimal esophagus contouring for predicting RE of breast cancer, and full-length esophagus contouring is not necessary.
Conclusion: Based on VBA, contouring the esophagus from the lower edge of the cricoid cartilage to the lower margin of the aortic arch is optimal for esophagus dose constrains in postmastectomy regional nodal radiotherapy.