S316
Clinical - Breast
ESTRO 2026
Purpose/Objective: The use of hypofractionated regimens in breast cancer radiotherapy (RT) has been steadily increasing and is currently recommended as a standard treatment in major guidelines. This study aimed to evaluate the association of two common acute adverse effects (AAEs) -dermatitis and dysphagia- with clinicopathological and dosimetric parameters in patients undergoing hypofractionated RT to the chest wall (CW) or whole breast (WB) combined with regional nodal irradiation (RNI). Material/Methods: Thirty-one breast cancer patients treated between 2022 and 2024 were retrospectively analysed. Computed-tomography (CT) simulation was performed using the deep-inspiration breath-hold (DIBH) technique with 2.5 mm slice thickness. All RT
plans were generated with hybrid intensity- modulated-RT (IMRT). Both CW and WB were
prescribed 40 Gy in 15 fractions, followed by a 10 Gy boost in 5 fractions to the tumor bed. A 0.5 cm bolus was applied to CW cases. AAEs were graded according to the Common Terminology Criteria for Adverse Events v5 (CTCAEv5). Results: The median follow-up was 5 months (range, 1–21). Patient and treatment characteristics are summarized in Table-1. Twenty-four patients (77%) underwent breast-conserving surgery, whereas seven (23%) had modified radical mastectomy. Sentinel lymph node biopsy was performed in 29% of patients (median = 2, range = 1–3). Twenty-five patients (81%) received adjuvant chemotherapy prior to RT, and all HER2- positive patients (n = 9, 29%) received trastuzumab + pertuzumab. Dermatitis was observed in 15 patients— 42% in CW-RT and 50% in WB-RT (p = 0.7)—including grade 1 in 13 (41.9%) and grade 2 in 2 (6.5%); no grade ≥ 3 AAEs occurred. Dysphagia was observed in 5 patients (16.1%), all grade 1. No associations were found between AAEs and comorbidities, smoking status, surgery type, hormone receptor status or tumor size. Dermatitis showed no correlation with Dmean, D2, D50, D98, or V107. In contrast, dysphagia correlated significantly with esophageal Dmean (p < 0.047), V15 (p < 0.031), V20 (p < 0.024), V25 (p < 0.018), V30 (p < 0.021), and V35 (p < 0.03). ROC analysis identified esophageal threshold values summarized in Table-2.
Conclusion: Hypofractionated RT for both CW and WB was well tolerated, with no grade ≥ 3 AAEs. While dermatitis remained mild and unrelated to dosimetric factors, dysphagia exhibited a dose-response relationship with esophageal dose parameters. These findings emphasize the clinical relevance of incorporating
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