S292
Clinical - Breast
ESTRO 2026
Controlled Trials and CINAHL and was performed in accordance with the PRISMA guidelines (PROSPERO ID: CRD42022298749) [3]. Studies published from 2005 onwards were considered eligible for inclusion, if they reported two or more risk factors for fibrosis or unfavorable cosmetic outcomes as primary outcomes. All studies using 2D-radiotherapy were excluded. Only prospective studies with a minimum sample size of 100 patients and a follow-up period of at least one year were included. A meta-analysis could not be performed due to the clinical and methodological heterogeneity of the studies included. Methodological quality and risk of bias were evaluated using the Quality in Prognosis Studies (QUIPS) tool and the Cochrane Risk of Bias tool. Patient, tumor, and treatment-related predictors were identified. Results: A total of twelve studies investigating 12.118 patients were included. Risk factors for both the development of fibrosis and unfavorable cosmetic outcomes were increasing age, larger tumor size, re-resection, poor early cosmetic outcomes before the start of radiotherapy, high boost dose, boost volume, homogeneity-index, dose whole breast irradiation, and adjuvant chemotherapy (Table 1). This review, however, could not identify specific risk factors in the context of BCT involving complex oncoplastic surgery techniques or following ultra-hypofractionated radiotherapy.
for complex post-reconstruction scenarios. These findings underscore a practical framework for future adaptive workflow development and multicentre standardization in reconstructed-breast radiotherapy. References: [1] Ohri N, Cahlon O, Ho AY, et al. Randomized trial of hypofractionated versus conventional postmastectomy radiotherapy for patients with implant reconstruction: Results of the FABREC trial. J Clin Oncol. 2023;41(15_suppl):506.[2] Wong JS, King TA, Hijal T, et al. Hypofractionated postmastectomy radiation therapy after implant-based breast reconstruction: a multicenter randomized clinical trial. JAMA Oncol. 2024;10(2):213–221. Keywords: POST MASTECTOMY RADIOTHERAPY, BREAST IMPLANTS Risk factors for breast fibrosis and unfavorable cosmetic outcomes after breast-conserving therapy in the contemporary era: a systematic review Marije C.A.W. Notenboom 1,2 , Wilma D. Heemsbergen 1 , Martine Franckena 1 , Linetta B. Koppert 3 , Marc A.M. Mureau 4 , Remi A. Nout 1 , Marian B.E. Menke-Pluijmers 2 , Femke E. Froklage 1 1 Radiotherapy, Erasmus MC Cancer Institute, University Medical Center, Rotterdam, Netherlands. 2 Surgery, Albert Schweitzer Hospital, Dordrecht, Netherlands. 3 Surgery, Erasmus MC Cancer Institute, University Medical Center, Rotterdam, Netherlands. 4 Plastic and Reconstructive Surgery, Erasmus MC Cancer Institute, University Medical Center, Rotterdam, Netherlands Purpose/Objective: Most evidence regarding risk factors for breast fibrosis and unfavorable cosmetic outcomes following breast- conserving therapy (BCT) comes from studies before the widespread introduction of 3D-conformal radiotherapy including Intensity-Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT), simultaneously integrated boost (SIB), and Digital Poster 3054 oncoplastic surgery techniques [1, 2]. It remains unclear whether established risk factors apply to modern 3D-radiotherapy (with or without ultra- hypofractionation) and simple or complex oncoplastic surgery. Therefore, this systematic review aimed to identify risk factors for fibrosis and unfavorable cosmetic outcomes following BCT in the context of current radiotherapy and oncoplastic surgery techniques. Material/Methods: A systematic literature search was conducted across Embase, Ovid Medline, Cochrane Central Register of
Conclusion: This systematic review identified candidate risk factors for breast fibrosis in the era of 3D-conformal radiotherapy. While most risk factors align with those reported in 2D-radiotherapy studies, dose homogeneity was additionally identified as a relevant factor. There was a lack of high-quality data on BCT
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