ESTRO 2025 - Abstract Book

S513

Clinical - Breast

ESTRO 2025

ipsilateral lung volume by 40% (mean absolute increase of 564 cc, p=0.02). CPAP resulted in an internal and caudal displacement of the heart with a mean increase of distance SC by 1.13 (0.56-1.7) cm and a mean decrease of ContactHeart by 1.42 cm compared with FB (Figure 1). These cardiac-thoracic anatomy changes induced by CPAP breathing, yielded a statistically significant reduction of heart subvolumes within tangential fields, with a decrease by 72% for HeartTg, 77.3% for LVTg and 66% for LADTg, compared to FB (all p=0.00).

Conclusion: CPAP use in left-sided breast cancer radiotherapy showed favourable changes in cardiac-thoracic anatomy, resulting in better heart sparing over FB. These data support the use of CPAP as an efficient and affordable alternative to advanced respiratory motion management RT techniques, especially in resource-limited radiation oncology departments.

Keywords: CPAP, thoracic anatomy, breast radiotherapy

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Mini-Oral Emulated target trial in the CANTO-RT cohort assessing tumor bed boost in post-menopausal breast cancer patients Simon Delaunay 1 , Noémie Simon-Tillaux 2,3 , Youssef Ghannam 1 , Thomas Sarrade 4 , Guillaume Auzac 1 , Youlia Kirova 5 , Séverine Racadot 6 , David Pasquier 7 , Barbara Pistilli 8 , Christelle Jouannaud 9 , Courèche Kaderbhai 10 , Laurence Vanlemmens 11 , Anne Kieffer 12 , Baptiste Sauterey 13 , Olivier Tredan 14 , Paul Cottu 15 , Christelle Levy 16 , Florence Lerebours 17 , Inès Vaz-Luis 8,18 , Fabrice André 8,18 , Catherine Gaudin 19 , Dominique Delmas 19 , Rodrigue Allodji 2,3 , Stefan Michiels 2,3 , Sofia Rivera 1,20 1 Radiotherapy Department, Gustave-Roussy, Villejuif, France. 2 Office of Biostatistics and Epidemiology, Gustave Roussy, Villejuif, France. 3 Oncostat U1018, Inserm, University Paris-Saclay, labeled Ligue Contre le Cancer, Villejuif, France. 4 Radiotherapy Department, Tenon hospital, Paris Sorbonne University, Paris, France. 5 Radiotherapy Department, Institut Curie, Paris, France. 6 Radiotherapy Department, Centre Léon Bérard, Lyon, France. 7 Radiotherapy Department, Centre Oscar Lambret, Lille, France. 8 Oncology Department, Gustave-Roussy, Villejuif, France. 9 Oncology Department, Institut Godinot, Reims, France. 10 Oncology Department, Centre Georges François Leclerc, Dijon, France. 11 Oncology Department, Centre Oscar Lambret, Lille, France. 12 Oncology Department, Institut de Cancérologie de Lorraine, Nancy, France. 13 Oncology Department, Institut de Cancérologie de l'Ouest, Angers, France. 14 Oncology Department, Centre Léon Bérard, Lyon, France. 15 Oncology Department, Institut Curie, Paris, France. 16 Oncology Department, Centre François Baclesse, Caen, France. 17 Oncology Department, Institut Curie, Saint-Cloud, France. 18 U1018, Inserm, University Paris-Saclay, Villejuif, France. 19 Data department, UNICANCER, Paris, France. 20 U1030, Inserm, University Paris-Saclay, Villejuif, France