S349
Clinical - Breast
ESTRO 2026
Purpose/Objective: Adjuvant external beam radiation therapy (EBRT) is an integral component for adequate locoregional control in breast cancer. However, irradiation of surrounding normal tissues raises concerns about toxicities. While the dosimetric advantages of Deep Inspiration Breath Hold (DIBH) are well established for left-sided breast cancers, emerging evidence suggests potential benefits even in right-sided cases, by reducing ipsilateral lung dose and exposure to cardiac substructures. This study evaluates the dosimetric parameters of DIBH and free breathing (FB) techniques in patients receiving adjuvant EBRT for right-sided breast cancer. Material/Methods: We performed a dosimetric analysis in a tertiary cancer institute, in patients with right-sided breast cancer post mastectomy/breast conservation surgery. Two sets of images were acquired during CT simulation for each patient: free breathing and DIBH. In addition to the target volumes for locoregional irradiation (in accordance with ESTRO contouring guidelines), the following structures were delineated as organs at risk (OARs)- heart, right lung, left breast, oesophagus, left anterior descending artery (LAD), individual cardiac chambers (left atrium, right atrium, left ventricle, right ventricle), superior (SVC) and inferior vena cavae (IVC), and aorta. EBRT plans were generated for both FB and DIBH techniques, and dosimetric parameters were subsequently analyzed statistically. Results: A total of 13 patients were included in this study, ranging from stages IIA-IV, wherein 6 patients received EBRT to a dose of 40 Gy in 15 fractions over 3 weeks, and 7 patients received a dose of 26 Gy in 5 fractions over 1 week. Nine patients received regional nodal irradiation (supraclavicular/ axillary/internal mammary nodes).Table-1 enumerates the median values of dosimetric parameters analyzed in this study.
endpoint was distant DFS (dDFS); secondary endpoints included breast cancer-specific survival (BCSS) and acute and late cardiopulmonary toxicities. Survival estimates were calculated using Kaplan-Meier analysis. Results: A total of 68 patients received IMNI. The median age was 51.5 years (range, 33–77). Fifty-four patients (79%) underwent mastectomy, and 14 (21%) underwent BCS. Left-sided disease was present in 36 cases (53%). The majority had invasive ductal carcinoma (81%) and high-grade tumors (G3, 56%). Biological subtypes included 50 luminal-like, 8 triple-negative, 5 HR+/HER2+, and 5 HR-/HER2+ tumors. Twenty-five patients received neoadjuvant chemotherapy with anthracyclines and taxanes; among these, 10 also received neoadjuvant and adjuvant trastuzumab. An additional 42 patients received adjuvant chemotherapy. The median follow-up was 8.6 years. The median dDFS was 9.1 years (range, 0.4–11.3), with 11 patients (16%) developing distant metastases. One patient relapsed at the internal mammary node, and one in the supraclavicular fossa. No local or axillary recurrences were observed. Median BCSS was not reached; 10 patients (15%) died of BC and one from unrelated causes.No acute pulmonary toxicities were reported. Late grade 1 pulmonary toxicity occurred in 5 patients (7%), and two left-sided cases (3%) developed late cardiac events (1 ischemic, 1 atrial
fibrillation). Conclusion:
In this retrospective cohort, IMNI was associated with sustained control of distant disease and minimal cardiopulmonary toxicity. Importantly, no excess cardiac mortality was observed, supporting the safety of IMNI in selected patients. References: 1. Effect of Elective Internal Mammary Node Irradiation on Disease-Free Survival in Women With Node-Positive Breast CancerA Randomized Phase 3 Clinical Trial. Kim Y.B et al. JAMA Oncol. 2022;8;(1):96- 105. doi:10.1001/jamaoncol.2021.6036 Keywords: breast cancer, IMNI
Digital Poster 5166 Comparative Dosimetric Analysis of Deep
Inspiration Breath Hold and Free Breathing for Adjuvant Radiotherapy in Right-sided Breast Cancer Antara Bagchi, Supriya Mallick, Anil Gupta, Adhar Amritt, Abhilash Dagar, Aman Sharma, Karun Kamboj, Vaishali Kataria Radiation Oncology, All India Institute of Medical Sciences, New Delhi, India
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