1061 - Prospective Cohort to Validate Predictive Models for Esophagitis in Breast Cancer Patients Undergoing Hypofractionated Regional Nodal Radiotherapy
Presenter(s)
D. Q. Wang1, N. Zhang2, X. Hou3, L. Yan4, H. F. Wu5, Y. Zhong6, X. Huang7, J. Jin8, Q. Zhong9, H. Jing8, T. Yu1, Y. W. Song10, Y. Liu8, S. Qi8, Y. Tang10, Y. Zhai10, H. Fang11, Y. X. Li12, and S. Wang10; 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, 22. Department of Radiation Oncology, Cancer Hospital of China Medical University, Liaoning Cancer Hospital & Institute, Shenyang, Liaoning, China, 3Department of Radiation Oncology, Peking Union Medical College Hospital, Chinese Academy of medical Sciences & Peking Union Medical College, Beijing, China, 4The First Hospital of Jilin University, Changchun, China, 5Department of Radiation Oncology, Jilin Cancer Hospital, Changchun, China, 6Department of Radiation and Medical Oncology, Zhongnan Hospital, Wuhan University, Wuhan, China, Wuhan, China, 7Department of Radiation Oncology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China, 8State 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, 9Department of Radiation Onoclogy, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China, 10State 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, 11State 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, 12National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
Purpose/Objective(s): Our previous study as training cohort found that the esophageal relative volumes receiving at least 25 Gy (RV25) and absolute volumes receiving at least 35 Gy (AV35) are the dose-volume predictors of =grade 2 radiation esophagitis (RE) with RV25 <20% and AV35 <0.27mL can serving as dose constraint for esophagus. Combination of right-side tumor and internal mammary nodal irradiation (IMNI) with either RV25 <20% or AV35 <0.27mL can each construct an effective predictive model (RV25 model, AV35 model) for =grade 2 RE. This prospective study as validation cohort enrolled similar group of breast cancer patients treated with a strict restriction on the esophagus RV25 and AV35, aimed to validate the performance of the previous predictive models.
Materials/Methods: 465 patients treated between January 11, 2022 and February 5, 2024 (minimum post-RT follow-up: 6 months) were included. All patients received chest wall, supraclavicular/infraclavicular fossa, level II axilla, and/or the internal mammary chain irradiation with IMRT or VMAT techniques after mastectomy. The prescribed dose was 43.5 Gy in 15 fractions. RE was evaluated weekly during RT and at 1 and 2 weeks, followed by 3 and 6 months after RT, and was graded according to the Common Toxicity Criteria for Adverse Events v3.0. The esophagus was contoured from the lower border level of the cricoid cartilage to the lower margin of the aortic arch. Esophageal total volume, mean dose, maximum dose, RV5–RV45 and AV5–AV45 by 5 Gy increments were evaluated. Area under curve (AUC) values were calculated to evaluate discrimination, and calibration curve with Hosmer-Lemeshow goodness-of-fit test (H-L) for calibration. Risk stratification was conducted using a decision tree analysis based on the number of risk factors.
Results: The grade 2 RE incidence was declined to 23.7% (110/465) as compared with 40.9% in the training cohort, and no grade 3 or higher RE was observed. RV25 in the validation cohort decreased from 10.9% in the training set to 4.6%, and the AV35 decreased from 0.1mL to 0mL. Predictive models both showed good discrimination and calibration. In RV25 model, AUC and H-L were 0.686 and 0.832 for training cohort, 0.688 and 0.974 for validation cohort. In AV35 model, AUC and H-L were 0.688 and 0.913 for training cohort, 0.651 and 0.776 for validation cohort. Risk factors included right side tumor, IMNI, RV25 <20% or AV35 <0.27mL. Patients with 0, 1 and 2-3 risk factors were assigned to the low-, intermediate-, and high-risk group. The incidence of =grade 2 RE in three risk groups were significantly distinct from each other (RV25 model: 14.8% vs. 24.7% vs. 48.3%; AV35 model: 14.7% vs. 23.7% vs. 45.4%).
Conclusion: External validation indicates that RV25 model and AV35 model perform well in predicting =grade 2 RE. Avoidance of unnecessary IMNI and maintaining the upper esophageal V25 at <20% and V35 at <0.27 mL may decrease the risk of RE.