S306
Clinical - Breast
ESTRO 2026
Varanasi, India. 2 Dept. of Medical Oncology, HBCH & MPMMCC, Tata Memorial Center, Homi Bhabha National Institute, Varanasi, India. 3 Dept. of Surgical Oncology, HBCH & MPMMCC, Tata Memorial Center, Homi Bhabha National Institute, Varanasi, India. 4 Dept. of Nuclear Medicine, HBCH & MPMMCC, Tata Memorial Center, Homi Bhabha National Institute, Varanasi, India. 5 Dept. of Pathology, HBCH & MPMMCC, Tata Memorial Center, Homi Bhabha National Institute, Varanasi, India. 6 Dept. of Radiodiagnosis, HBCH & MPMMCC, Tata Memorial Center, Homi Bhabha National Institute, Varanasi, India Purpose/Objective: Presence of gross internal mammary node (IMN) in breast cancer patients is considered a high-risk feature. [1,2] Outcome data for prophylactic radiotherapy (RT) of IMN and other nodal areas are available. However, data on treatment outcomes in presence of gross IMN and use of hypo-fractionated RT in such scenario is lacking in literature. The present study assessed the real-world outcomes in IMN positive breast cancer patients treated with hypo- fractionated RT. Material/Methods: The study is a retrospective analysis of a prospectively maintained database of IMN positive breast cancer patients treated with hypo-fractionated adjuvant breast RT in a North Indian tertiary cancer centre, between March 2020 to December 2024. These patients had received a dose of 40Gy/15 fractions/3 weeks with or without tumour bed boost to the primary site and regional nodal area, including IMN. The demographic details, disease characteristics, treatment parameters and outcomes (from date of diagnosis) were collected and analysed using SPSS V30. Results: In a total of 147 patients, median age at presentation was 49 years and the median follow up period was 30 months. Eighty six of 147 (58.5%) patients had left sided or bilateral breast cancer with 130 of 147(88.4 %) patients having Grade III tumors. One hundred six (72.2 %) patients had T3 or T4 tumors with 137(93.2%) patients having N3b disease and stage IIIc disease was seen in 140(95.2%) patients. Twenty-one (16%) of 131 (89.1% of the total 147) patients who received neo- adjuvant chemotherapy (NACT) showed pathological complete response. One hundred twenty-six (85.7%) patients underwent modified radical mastectomy. All eligible patients received Her 2 directed and/or hormonal therapy. CDK inhibitors and maintenance Capecitabine were used in only 17.5 % and 60.5 % of eligible patients, respectively. With respect to RT, all patients were treated with Arc Therapy and 32(21.8%) of them were treated with DIBH technique. Disease
Conclusion: Adjuvant radiotherapy for breast cancer, including supraclavicular nodal irradiation, is not associated with an increased risk of thyroid dysfunction at 5 years. These findings support the safety of hypofractionation and current thyroid dosimetric guidelines. While radiotherapy-related factors were not predictive, higher BMI was identified as a significant risk factor for developing thyroid dysfunction. Therefore, while routine thyroid monitoring may not be necessary for all patients, it could be considered for patients with a high BMI. References: 1. Smith GL et al. Risk of hypothyroidism in older breast cancer patients treated with radiation. Cancer. 2008 Mar15;112(6):1371–9.2. Darvish L et al. Evaluation,of thyroid gland as an organ at risk after breast cancer radiotherapy: a systematic review and meta-analysis. Clin Transl Oncol. 2018 Nov;20(11):1430–8.Funding source:The HypoG-01 trial is funded by the French National Institute of cancer (INCA; grant reference: PHRC-K 15-146). The funders were not involved in the study design, in the collection, analysis, or interpretation of date, the writing of the manuscript, or the decision to submit the manuscript for publication.The full trial protocol and trial manual are avaible upon request from the sponsor at: hypog- 01@unicancer.fr. Keywords: Breast Cancer, Thyroid dysfunction, Radiotherapy Real World Outcome in Internal Mammary Node Positive Breast Cancer Patients Treated with Hypo- fractionated Radiotherapy in a Tertiary Center in India Lincoln Pujari 1 , Prashanth Giridhar 1 , Pritam Mondal 1 , Chaturbhaj Rajgopal Khandelwal 1 , Samapika Bhaumik 1 , Jhansi Pattanaik 1 , Subham Dokania 1 , Tanvee Shingla 1 , Ankita Rungta Kapoor 1 , Avradeep Dutta 1 , Abhishek Shinghal 1 , Ashutosh Mukherji 1 , Satyajit Pradhan 1 , Anuj Gupta 2 , Mayank Tripathy 3 , Arvind Suresh 4 , Ipsita Dhal 5 , Shreya Shukla 6 1 Dept. of Radiation Oncology, HBCH & MPMMCC, Tata Memorial Center, Homi Bhabha National Institute, Digital Poster 3582
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