S333
Clinical - Breast
ESTRO 2026
Amamoo 2 , Montserrat Pazos 3 , Stefanie Corradini 4 , Stephanie E. Combs 1 , Kai Borm 1 1 Department of Radiation Oncology, School of Medicine and Klinikum rechts der Isar, Technical University of Munich, Munich, Germany. 2 R. Ken Coit College of Pharmacy, University of Arizona, Tucson, USA. 3 Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany. 4 Department of Radiation Oncology, University Hospital, Erlangen, Germany Purpose/Objective: Optimal locoregional management of breast cancer recurrences after prior radiotherapy remains a clinical challenge. Given the increased risk of local failure in these cases, a second course of radiotherapy may be considered, including for those undergoing repeat breast-conserving surgery (BCS), to avoid mastectomy. Prospective evidence supporting re-irradiation (reRT) is largely lacking, and retrospective data are most robust for reRT with brachytherapy. However, external beam reRT represents the most applied treatment technique due to its wide availability. This systematic review synthesizes the current evidence on the feasibility, efficacy, toxicity, and patient-reported quality of life outcomes associated with external beam re-irradiation for locoregional breast cancer Material/Methods: Following PRISMA guidelines (PROSPERO CRD420251003760), seven databases were searched through February 18, 2025. Eligible studies investigated adjuvant external beam reRT for ipsilateral breast or chest-wall recurrence after surgery, reporting on disease control, survival, toxicity, or patient-reported outcomes. Data were extracted and summarized descriptively. Results:
Twenty-two studies comprising 1,239 patients ( ≈ 1,184 unique) were included. Most of them were retrospective, single-institution analyses; one was a prospective Phase II trial. Median re-irradiation doses ranged from 40–55 Gy, with curative-intent partial- breast regimens achieving 2–5 year local control rates of 80–100% and overall survival up to 95%. Across all studies, 2,604 toxicity events were reported, predominantly mild (Grade 1–2 in >90%). Grade ≥ 3 toxicity occurred in about 8% of all reported adverse events, 4.9% acute and 3.3% late, most commonly presenting as fibrosis, breast induration, or ulceration. Higher cumulative EQD ₂ values were associated with an increased likelihood of developing severe (Grade ≥ 3) toxicity. Patient-reported outcomes and quality of life data were scarce. Conclusion: External beam reRT following repeat BCS or chest-wall surgery is feasible and yields durable local control with acceptable toxicity in appropriately selected patients. Modern conformal techniques, careful dose selection, and limited treatment volumes improve safety while maintaining oncologic efficacy. However, heterogeneity in reporting, absence of randomized comparisons, and limited inclusion of patient-reported endpoints underline the need for standardized, prospective, multicenter studies to define optimal dose regimens, cumulative dose constraints, and selection criteria. Funding: This study was funded by the Else Kröner-Fresenius Foundation. Keywords: breast cancer, recurrence, re-irradiation Evaluation of Setup Margins in Breast Cancer Treated with Volumetric Modulated Arc Therapy Nejla Fourati, Rim Trigui, Fatma Missaoui, Leila Farhat, Wafa Mnejja, Jamel Daoud Radiation Oncology, Habib Bourguiba teaching hospital, Sfax, Tunisia Purpose/Objective: Three-dimensional conformal radiotherapy (3D-CRT) remains the reference technique in the treatment of breast cancer. Volumetric Modulated Arc Therapy (VMAT) may be indicated in complex cases. However, Digital Poster 4687
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