S204
Clinical - Breast
ESTRO 2026
2025 to 05-05-2025 across our nationwide network of 8 centers. All sites were asked to recontour esophagus based on the paper and share mean dose before and after recontouring. Based on the results the contouring guidelines of esophagus was revised for the network and one site tracked incidence of esophagitis before and after the change. Results: All but one site used auto segmentation generated entire esophagus as denominator. The mean dose and IQR was 6.1 Gy (IQR 4.7–7.9) and after revision as expected it increased to 11.7 Gy (IQR 8.6–15.1). Across 43 plans, SOP contours yielded significantly higher esophageal Mean (median 9.6 Gy vs. 5.7 Gy; p < 0.001, Wilcoxon signed-rank). Dmax was (30.8 vs. 27.4 Gy; p = 0.047), while V20 increased from 5.1% to 9.4% (p = 0.031). Importantly, 16/42 patients (38.1%) had a mean esophageal dose >11 Gy after recontouring. In the 7- patient series from one site, 6/7 pre-change developed Grade 2 esophagitis, compared with 0/7 post-SOP patients (Fisher’s exact test, p = 0.004). Clinical comparison showed that patients with no esophagitis post-SOP had mean esophageal doses around 7–10 Gy, distinctly lower than the 12–13 Gy range observed in patients who developed Grade 2 esophagitis pre- SOP. The mean esophageal dose after SOP modification averaged 10.8 Gy, remaining within the <11 Gy recommended constraint. Conclusion: The audit identified systemic error which led to higher than desired mean dose to esophagus causing Grade 2 esophagitis. Our current network guidelines and clinical goals addresses these with revised guidelines for the network. As the use of VMAT and auto- segmentation has increased, it is important information for institutions to audit and standardize their practices. References: 1. Wang W et al. Radiother Oncol. 2023; 182:109615.2. Yaney A et al. Pract Radiat Oncol. 2024;14(2): e123- e131.3. Offersen BV et al. Radiother Oncol. 2022; 170:30-41. Keywords: PMRT, Esophagus contouring, Dosimetric audit. Digital Poster 282 Recurrence patterns in stage III locally advanced breast cancer after post-mastectomy radiotherapy: a retrospective analysis Solin Onder 1 , Barbaros AYDIN 1 , Ali İ brahim Sevinc 2 , Hulya Ellidokuz 3 , Ilknur Gorken 1 1 Radiation Oncology, Dokuz Eylul University, Izmir, Turkey. 2 General Surgery, Dokuz Eylul University, Izmir, Turkey. 3 Public Health, Dokuz Eylul University, Izmir, Turkey
versus 3 weeks (FAST-Forward): 5-year efficacy and late normal tissue effects results from a multicentre, non-inferiority, randomised, phase 3 trial. The Lancet 2020; 395(10237): 1613–1626.2. Chatterjee S, Chakrabarty S, Santosham R, Saha A, Mallick I, Arunsingh M, Bhattacharya T, Achari R, Agrawal S, Ahmed R, Das J, Mahata A, Mandal S, Ray S. Alleviating Morbidity From Locally Advanced Breast Cancer Using a Practical and Short Radiation Therapy Regimen: Results of the HYPORT Palliative Studies. Int J Radiat Oncol Biol Phys. 2023 Aug 1;116(5):1033-1042. doi: 10.1016/j.ijrobp.2023.02.008. Epub 2023 Mar 2. PMID: 36868522. Keywords: Radiotherapy, ultrahypofractionation, palliative Digital Poster 279 Impact of Standardized Esophagus Contouring and Constraints in VMAT-based Postmastectomy Radiotherapy: A Network Quality Audit Report. MANJINDER SINGH SIDHU 1 , SUSHIL BERIWAL 2 , DEEPAK ABROL 3 , PRACHI KALRA 4 , SUMEET AGGARWAL 4 , SHUBHAM MITTAL 5 , CHANDANI VIJAYKUMAR HOTWANI 6 , MOHAN LAL 7 1 RADIATION ONCOLOGY, DAYANAND MEDICAL COLLEGE & HOSPITAL CANCER CARE CENTER IN COLLABORATION WITH AMERICAN ONCOLOGY INSSTITUTE.CANCER CENTER, LUDHIANA ,PUNJAB, India. 2 RADIATION ONCOLOGY, ALLEGHENY HEALTH NETWORK, PITTSBURGH, India. 3 RADIATION ONCOLOGY, AMERICAN ONCOLOGY INSTITUTE, JAMMU, INDIA, India. 4 RADIATION ONCOLOGY, AMERICAN ONCOLOGY INSTITUTE, HISAR,HARYANA, India. 5 RADIATION ONCOLOGY, AMERICAN ONCOLOGY INSTITUTE, GANGANAGAR, India. 6 RADIATION ONCOLOGY, AMERICAN ONCOLOGY INSTITUTE, NAGPUR, India. 7 RADIATION ONCOLOGY, AMERICAN ONCOLOGY INSTITUTE, HISAR, India Purpose/Objective: PMRT when treated with VMAT compared to 3D technique delivers higher average esophageal doses. There are few recent studies which have defined dosimetric constraints when treating regional node to reduce the unwanted incidence of grade 2 esophagitis. The mean dose is suggested to be less than 11 Gy. The denominator of esophagus in these papers was defined from cricoid to tracheal bifurcation while our network uses autosegmentation software which contours entire esophagus. We discussed these papers in our recent educational forum which led to this quality audit to see the practice of assessing esophagus constraints and its impact on side effects. Material/Methods: The audit analyzed 43 most recent cases from 10-03-
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