ESTRO 2025 - Abstract Book

S545

Clinical - Breast

ESTRO 2025

treatment outcomes based on tumor biology. Further studies are recommended to validate these results in larger, multi-center studies.

Keywords: Breast cancer, Hypofractionation, radiotherapy

References: Demircan NV, Bese N. New approaches in breast cancer radiotherapy. Eur J Breast Health. 2023;20(1):1–7.

[2] Horeweg N, Nout RA, Jürgenliemk-Schulz IM, et al. Molecular classification predicts response to radiotherapy in the randomized PORTEC-1 and PORTEC-2 trials for early-stage endometrioid endometrial cancer. Journal of Clinical Oncology [Internet]. 2023 [cited 2024 Nov 12];41(27):4369–4380.

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Digital Poster Outcome of Extreme Hypofractioned breast radiotherapy in locally advanced breast cancer. LINCOLN PUJARI, Prashanth Giridhar, Satyajit Pradhan, Samapika Bhaumik, Chaturbhuj Rajgopal Khandelwal, Chandrima Mukherji, Ankita Rungta Kapoor, Abhishek Shinghal Dept of Radiation Oncology, HBCH & MPMMCC, Tata Memorial Center, Homi Bhabha National Institute, Varanasi, India Purpose/Objective: To compare the outcome of Extreme Hypofractionated Radiotherapy (Ex-HFRT) and Moderately Hypofractionated radiotherapy (Mo-HFRT) in locally advanced breast cancer requiring nodal irradiation. Material/Methods: It is a retrospective analysis of prospectively maintained database of locally advanced (Stage III AJCC 8th) invasive carcinoma of breast patients who received adjuvant breast radiotherapy either with Ex-HFRT (26Gy/5#s +/- Tumor bed boost) or Mo-HFRT (40Gy/15#s +/- Tumor bed boost) in a tertiary care institute in India from March 2020 to Dec 2021. The demographic, treatment characteristics and survival outcomes were collected and analyzed by SPSS V27. Results: Median age at presentation is 47 Years in total 351 patients. 54.1% patients had left sided breast tumors. 89.2 % (313/351) patients had Grade III tumors. 278/351 (79.2%) patients had T3/T4 lesion and (210/351) 59.9%% patients had N2 or N3 disease with 40% of patient with nodal disease showing extra nodal extension in final histopathology. 289/351 patients (82.3%) received NACT and among them 45 patients (12.8%) had pCR. 299/351 (85.2%) patients underwent MRM. 42.5% patients (149/351) were Hormone positive and 21.9% patients were triple negative. 72.8% (91/125) of eligible patients completed 12 months of anti-Her therapy. 322/351 (91.8%) patients were treated with 3DCRT technique. All the parameters were comparable among both groups except response to NACT which was better in Mo-HFRT. After a Median follow up of 46 months and 92 events, the 4 Year DFS was significantly better in Ex-HFRT arm (80.4% Vs 66.7% (p=0.027)) (Fig. -1) while the difference in OS was insignificant. (86.2% Vs 80.8% (p=0.25)) (Fig. - 2) as compared to Mo-HFRT arm.