S218
Clinical - Breast
ESTRO 2026
combined use of MH for both breast and axilla is being challenged. The SKAGEN study found no significant differences in locoregional failure, distant metastasis, or mortality between the 40 Gy/15 and 50 Gy/25 regimens, though it did report increased breast cancer mortality in the 40 Gy/15 group. In contrast, our real world results showed an overall survival closer to the conventional fractionation arm of the trial, keeping a low toxicity profile. References: Krug D. et al. (2021). Moderate hypofractionation remains the standard of care for whole-breast radiotherapy in breast cancer: Considerations regarding FAST and FAST-Forward.Strahlenther Onkol, 197(4):269–280. https://doi.org/10.1007/s00066-020- 01744-3Annals of Oncology (2024) 35(suppl_2):S309– S348. https://doi.org/10.1016/annonc/annonc1577Offersen B.V. et al. The SKAGEN Trial 1 protocol: Moderately hypofractionated loco-regional adjuvant radiotherapy of early breast cancer combined with a simultaneous integrated boost (DBCG HYPO II). DBCG, v1.0, 01/02/2015. ClinicalTrials.gov: NCT02384733. Keywords: Locoregional Treatment; Moderate Hypofractionation Adjuvant radiotherapy in early-stage luminal breast cancer: particularly in older patients radiotherapy is more frequently omitted Lotte Bouwman 1 , Erik J Blok 2 , Astrid Scholten 3 , Sabine Siesling 4,5 , Johanneke E.A. Portielje 2 , Gerrit Jan Liefers 1 1 Department of Surgery, Leiden University Medical Center, Leiden, Netherlands. 2 Department of Medical Oncology, Leiden University Medical Center, Leiden, Netherlands. 3 Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, Netherlands. 4 Department of Research and Development, Netherlands Comprehensive Cancer Organisation (IKNL), Utrecht, Netherlands. 5 Department of Health Technology and Services Research, Technical Medical centre, University of Twente, Enschede, Netherlands Purpose/Objective: To evaluate national trends in the administration of adjuvant radiotherapy (RT) after breast-conserving surgery (BCS) in women aged 50 years and older, with early-stage hormone-receptor (HR) positive breast cancer (BC) between 2014 and 2024 in the Netherlands. Material/Methods: This descriptive study included women aged ≥ 50 years old with estrogen receptor-positive, HER2-negative, non-metastatic BC, treated with BCS between 2014 Digital Poster 818
Digital Poster 785 Locoregional Treatment with Moderate Hypofractionation in Breast Cancer – Experience from a Single Center Inês Sá Couto, Filipa Martins, Catarina Van der Elzen, Alice Alves, Fátima Aires, Catarina Dias, João Casalta- Lopes, Pedro Meireles, Lígia Osório Radiotherapy, ULS São João, Oporto, Portugal Purpose/Objective: Adjuvant radiotherapy (RT) plays a key role in breast cancer treatment. Several clinical trials have validated moderate hypofractionation (MH) as an effective adjuvant RT regimen. However, its use in regional nodal irradiation remains limited, with some centers still favoring conventional fractionation due to toxicity concerns. This study aims to provide real world data on the adjuvant locoregional irradiation setting using MH. Material/Methods: A retrospective review was conducted of female breast cancer patients treated with adjuvant locoregional RT using MH between 2015-2019. Data were collected from our centre database. Statistical analysis was performed with IBM SPSS v29. Results: 60 patients were included, with a mean age of 54 years and a median follow-up of 41.7 months. Most had stage I–II disease. Breast-conserving surgery was performed in 73.3%, sentinel lymph node biopsy in 80%, and axillary dissection in 35%. Hormone therapy was administered in 76.7%, neoadjuvant chemotherapy in 40%, adjuvant chemotherapy in 31.7%, and trastuzumab in 25%. All received 40 Gy in 15 fractions, including breast and axilla, with a boost in 41.7%. Five-year overall, local disease-free, regional disease-free, and distant disease-free survival were 92.1%, 98.1%, 98.1%, and 85.1%, respectively. No grade 3 toxicities occurred. Grade 1 arm lymphedema and fibrosis were observed in 6.7% each, grade 2 fibrosis in 1.7%, and grade 1 breast edema in 5%. No brachial plexopathy was detected. Conclusion: Concerns about potential increased toxicity associated with locoregional RT using MH have limited the widespread adoption of this approach in several countries. The results presented demonstrate the efficacy and safety of MH in this patient cohort, highlighting excellent overall survival and disease-free survival (local, regional, and distant) with a median follow-up of 41.7 months. The preliminary results of the SKAGEN Trial 1 showed an increased risk of 5y breast cancer mortality (overall mortality) with 7.2% (9.9%) in the MH group versus 5.1% (7.9%) in the control arm. Our overall mortality approaches the one from the control arm.Scientific evidence on the
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