ESTRO 2025 - Abstract Book

S452

Clinical - Breast

ESTRO 2025

Conclusion: This study suggests that TR and NP dichotomy based on tumor histology and topography does not necessarily support the therapeutic consequences for TR. In case of late TR (“TR like”), a 2 nd BCT could be carefully discussed for patients who wish to preserve their breast. New tools are needed to refine 2 nd iBCE definition.

Keywords: Breast cancer recurrence

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Proffered Paper Salvage treatment for HER2+/Triple negative 2nd ipsilateral breast cancer event: A propensity score matched cohort analysis of the GEC-ESTRO database Jean-Michel Hannoun-Levi 1 , Jocelyn Gal 2 , Renaud Schiappa 2 , Viktor Smanyko 3 , Daniela Kauer-Domer 4 , David Pasquier 5 , Claire Lemanski 6 , Séverine Racadot 7 , Gilles Houvenaeghel 8 , Benjamin Guix 9 , Aurélie Belliere-Calandry 10 , Kristina Loessl 11 , Bülent Polat 12 , Cristina Gutierrez 13 , Razvan Galalae 14 , Csaba Polgar 15 , Vratislav Strnad 16 1 Radiation Oncology, Antoine Lacassagne Cancer Centre, University Cote d’Azur, Nice, France. 2 Epidemiology and Biostatistics, Antoine Lacassagne Cancer Centre, University Cote d’Azur, Nice, France. 3 Radiation Oncology, National Institute of Oncology, Budapest, Hungary. 4 Radiation Oncology, Medical University of Vienna, Vienna, Austria. 5 Radiation Oncology, Oscar Lambret Cancer Centre, Lille University, Lille, France. 6 Radiation Oncology, Montpellier Val d'Aurelle Cancer Institute, Montpellier, France. 7 Radiation Oncology, Leon Berard Cancer Centre, Lyon, France. 8 Surgical Oncology, Paoli-Calmettes Institute, CRCM, Aix Marseille University, Marseille, France. 9 Radiation Oncology, Medical Institute for Radiotherapy & Oncology, Barcelona, Spain. 10 Radiation Oncology, Auvergne Jean Perrin Cancer Centre, Clermont-Ferrand, France. 11 Radiation Oncology, Inselspital, Bern University Hospital, Bern, Switzerland. 12 Radiation Oncology, University of Wurzburg, Wurzburg, Germany. 13 Radiation Oncology, Catalan Institute of Oncology, Barcelona, Spain. 14 Radiation Oncology, MedAustron Centre for Ion Therapy and Research, Vienna, Austria. 15 Radiation Oncology, National Institute of Oncology, Budapest, Hungary and Department of Oncology, Semmelweis University, Budapest, Hungary. 16 Radiation Oncology, Erlangen University Hospital, Erlangen, Germany Purpose/Objective: Second breast conserving treatment (2 nd BCT) has emerged as an option for patients with low-risk second ipsilateral breast cancer event (2 nd iBCE) after primary breast conserving treatment (BCT) combining lumpectomy and irradiation. However, over-expression of HER2 (HER2+) or triple negative (TN) molecular subtypes are generally considered bad candidates for 2 nd BCT. We aimed to address the lack of evidence regarding local treatment of