S2969
Late-Breaking
ESTRO 2026
22 Department of Radiation Oncology, Institut Curie, Paris, France. 23 Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, Netherlands. 24 Department of Radiation Oncology, HMC the Hague, Leidschendam, Netherlands. 25 Department of Radiation Oncology, Iridium Netwerk, Wilrijk-Antwerp, Belgium. 26 Faculty of Medicine and Health Sciences, University of Antwerp, Wilrijk- Antwerp, Belgium Purpose/Objective: The EORTC trial 22922/10925 investigates the impact of the internal mammary and medial supraclavicular (IM-MS) radiation therapy (RT) for stage I-III breast cancer patients (Clinicaltrials.gov NCT00002851). We hereby present the results of the scheduled long-term analysis with 22.2 years median follow-up. Material/Methods: Eligible patients had involved axillary lymph nodes (LN) and/or a centrally/medially located primary tumour. Randomisation was for IM-MS RT. The trial aimed at detecting an OS hazard ratio (HR) of 0.82, corresponding to an increase in 10-year OS rate from 75 to 79% at 5% significance level and 80% power. Secondary endpoints were disease-free survival (DFS), distant metastases-free survival (DMFS), breast cancer mortality (BCM), breast cancer recurrence (BR), and late side-effects. Twenty-years’ effects were analysed using Kaplan-Meier method, cumulative incidence curves and unadjusted Cox and Fine-Gray models, accordingly, at the same 5% significance level. Results: Between 1996 and 2004, 4004 patients were randomised. Median age was 54 years; 55.6% had involved axillary LN. Nearly all LN-positive (99.0%) and 66.3% of LN-negative patients received adjuvant systemic treatment. At a median follow-up of 22.2 years, 1550 (38.7%) patients died, of whom 796 (51.4%) due to breast cancer. At 20 years, OS rate was 61.0% versus 61.8% (HR=1.00; 95%CI: 0.90-1.10; P=0.967); DFS was 48.2% versus 49.0% (HR=0.97; 0.89- 1.06; P=0.515); DMFS was 58.9% versus 59.8% (HR=0.97; 0.88-1.08; P=0.578); and BR was 27.3% versus 30.2% (HR=0.88; 0.78-0.99; p=0.037), with and without IM-MS RT, respectively.While BCM incidence was 18.6% versus 22.4% (HR=0.82; 0.72-0.95; P=0.006), the cumulative incidence of death not due to breast cancer (including cause unknown) was 20.4% versus 15.8% (HR=1.26; 1.09-1.46; p=0.002) with and without IM-MS RT, respectively.No differences were seen for the cumulative incidence of other events, including any second cancer (±23% in both arms) and second breast cancer (±10% in both arms). Lung fibrosis, cardiac fibrosis and cardiac diseases were more frequently reported after IM-MS-RT: 6.3% vs 3.2%, 2.7% vs 1.7% and 15.2% vs 11.7%,
reaffirm the use of 48Gy SIB in this population as standard of care. Keywords: breast, radiotherapy, boost
Proffered Paper 5580
Internal Mammary and Medial Supraclavicular irradiation in stage I-III breast cancer: 20 years results of the randomised EORTC trial 22922/10925. Orit Kaidar-Person 1,2 , Caroline G Weltens 3,4 , Catherine Fortpied 5 , Luc J Scheijmans 6 , Carine Y Kirkove 7 , Volker Budach 8,9 , Karine Peignaux-Casasnovas 10 , Mariacarla Valli 11,12 , Max Peters 13 , Femke van der Leij 14 , Sofia Rivera 15 , Nicola Weidner 16 , Desirée van den Bongard 17 , Claudia Linsenmeier 18 , Roxolyana Abdah-Bortnyak 19 , Shaymaa Hosni 20 , Eveline Koiter 21 , Antoine M Engelen 6 , Adinda Baten 3,4 , Lydia Champezou 5 , Alain Fourquet 22 , Harry G Bartelink 23 , Henk Struikmans 24 , Philip M Poortmans 25,26 1 Breast Radiation Unit, Sheba Medical Center, Ramat Gan, Israel. 2 Gray Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv, Israel. 3 Department of Radiation Oncology, University Hospitals Leuven, Leuven, Belgium. 4 Laboratory of Experimental Radiation Oncology, KU Leuven, Leuven, Belgium. 5 European Organisation for Research and Treatment of Cancer, Headquarters, Brussels, Belgium. 6 Department of Radiation Oncology, Institute Verbeeten, Tilburg, Netherlands. 7 Department of Radiation Oncology, University Hospital Saint Luc, Université Catholique de Louvain, Brussels, Belgium. 8 Department of Radiation Oncology, Comprehensive Cancer Center, Charité – University Medicine Berlin, Berlin, Germany. 9 Radiation Oncology, Vosspalais, Berlin, Germany. 10 Department of Radiation Oncology, Centre Georges François Leclerc, Dijon, France. 11 Department of Radiation Oncology, Sant Anna Hospital, Como, Italy. 12 Department of Radiation Oncology, Ospedale Valduce, Como, Italy. 13 Department of Radiation Oncology, Radiotherapiegroep, Deventer/Arnhem, Netherlands. 14 Department of Radiation Oncology, University Medical Centre Utrecht, Utrecht, Netherlands. 15 Department of Radiation Oncology, Gustave Roussy Cancer Centre, Villejuif, France. 16 Department of Radiation Oncology, University Hospital, Tübingen, Germany. 17 Department of Radiation Oncology, Cancer Center Amsterdam, Amsterdam UMC, Amsterdam, Netherlands. 18 Department of Radiation Oncology, University Hospital Zürich, Zürich, Switzerland. 19 Department of Radiation Oncology, The Joseph Fishman Oncology Center, Rambam Health Care Campus, Haifa, Israel. 20 Clinical Oncology, Nottingham University Hospitals NHS Trust, Nottingham, United Kingdom. 21 Department of Radiation Oncology, Medisch Spectrum Twente, Enschede, Netherlands.
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