ESTRO 2025 - Abstract Book

S516

Clinical - Breast

ESTRO 2025

Conclusion: This emulated trial based on real-world data did not find any significant effect of tumor bed boost regarding IBCFS in post-menopausal patients. Subgroups and toxicity endpoints will be explored in the future.

Keywords: Boost, emulated trial, breast cancer free survival

References: 1.

Bartelink H et al. Whole-breast irradiation with or without a boost for patients treated with breast-conserving surgery for early breast cancer: 20-year follow-up of a randomised phase 3 trial. The Lancet Oncology. janv 2015;16(1):47-56. 2. Collette S et al. Predictors of the risk of fibrosis at 10 years after breast conserving therapy for early breast cancer: a study based on the EORTC Trial 22881-10882 « boost versus no boost ». Eur J Cancer. nov 2008;44(17):258799. 3. Sarrade T et al. CANTO-RT: One of the Largest Prospective Multicenter Cohort of Early Breast Cancer Patients Treated with Radiotherapy including Full DICOM RT Data. Cancers. 25 janv 2023;15(3):751

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Digital Poster Could thoracic anatomy be used to predict lung irradiation in breast cancer radiotherapy? Zeineb Naimi, Abir Boubaker, Meriem Skouri, Raouia Ben Amor, Awatef Hamdoun, Ghada Bouguerra, Rihab Haddad, Lotfi Kochbati Radiation Oncology Department, Abderrahmen Mami Hospital, Ariana, Tunisia Purpose/Objective: The aim of this study was to identify anatomic predictors of lung radiation exposure in 3D conformal breast cancer radiotherapy. Material/Methods: Data of patients referred for adjuvant breast cancer radiotherapy was analysed. All patients were planned for hypofractionated radiotherapy with a prescription dose of 40Gy/15 fractions +/- an additional boost to the tumor bed. Treatment plans were generated with 3D conformal technique using tangential fields +/-supraclavicular field. All plans aimed to meet target volume coverage objectives and OAR dose constraints. For each patient, metrics related to both CTV (breast/chest wall) and ipsilateral lung anatomy, were measured on the planning CT. The CTV-dependant metrics were the CTV volume (CTVvol) and midplane CTV thickness (CTVTh). The lung-dependant metrics (Figure 1) were: the lung volume (LV), central lung distance (CLD): largest extent of the ipsilateral lung beyond the breast tangent on axial slices and the maximal lung width (MLW): the maximal chord length of breast tangent through the ipsilateral lung on axial slices. Dose distribution to ipsilateral lung was statistically analysed with regards to patient’s specific anatomy metrics using Pearson correlation and linear regression analysis.