ESTRO 2025 - Abstract Book

S540

Clinical - Breast

ESTRO 2025

achieving robust systemic control and minimizing adverse outcomes, urging closer collaboration in systemic and local treatment planning. There is a need for further research to reduce the SRN risk in breast cancer patients on targeted therapies.

Keywords: SRS,Targeted therapy ,Radiation necrosis

References: B. Id Said et al. , “Trastuzumab emtansine increases the risk of stereotactic radiosurgery-induced radionecrosis in HER2 + breast cancer,” J Neurooncol , vol. 159, no. 1, pp. 177–183, Aug. 2022, doi: 10.1007/s11060-022-04055-y.

2748

Digital Poster Repeat lumpectomy and external beam radiation therapy for ipsilateral breast cancer recurrence: a systematic review Shirley SW Tse 1,2 , Caroline Hircock 3 , Irene Karam 4 , Hany Soliman 4 , Shing Fung Lee 5,6 , J. Isabelle Choi 7 , Jeffrey Q. Cao 8,9 , Tarek Hijal 10 , Mylin Torres 11 , Gustavo Nader Marta 12 , Adrian W Chan 4 , Danielle Rodin 13,4 , C. Anne Koch 13,4 , Alyssa Wang 4 , Edward Chow 4 , Henry CY Wong 14 1 Department of Clinical Oncology, United Christian Hospital, Hong Kong, Hong Kong. 2 Department of Clinical Oncology, Queen Elizabeth Hospital, Hong Kong, Hong Kong. 3 Department of Medicine, McMaster University, Toronto, Canada. 4 Department of Radiation Oncology, University of Toronto, Toronto, Canada. 5 Department of Radiation Oncology, National University Hospital,, Singapore, Singapore. 6 Department of Medicine, Yong Loo Lin School of Medicine, Singapore, Singapore. 7 Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, USA. 8 Department of Oncology, University of Calgary, Calgary, Canada. 9 Department of Oncology, Arthur Child Comprehensive Cancer Centre, Calgary, Canada. 10 Department of Oncology, McGill University, Montreal, Canada. 11 Department of Radiation Oncology, Emory University, Atlanta, USA. 12 Department of Radiation Oncology, Hospital Sírio-Libanês, São Paulo, Brazil. 13 Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Canada. 14 Department of Clinical Oncology, Princess Margaret Hospital, Hong Kong, Hong Kong Purpose/Objective: Salvage mastectomy is the standard of care for breast cancer patients with ipsilateral breast recurrence (IBR) after breast-conserving surgery (BCS) and post-operative radiotherapy (RT). Emerging data suggests that repeat breast conserving therapy (BCT) could serve as a potential alternative. This systematic review aims to evaluate the effectiveness and safety of external beam RT (EBRT) as an accessible modality for repeat BCT. Material/Methods: A systematic literature search was conducted on MEDLINE, Embase, and Cochrane Central Register of Controlled Trials from database inception until September 22, 2024. Clinical studies that investigated the use of second BCT (repeat BCS + post-operative RT) using EBRT were included. Information on treatment technique, oncological efficacy and toxicities were extracted. Results: Nine articles representing 8 studies (1 prospective and 7 retrospective cohort studies) and 569 patients, were included. Most studies involved patients with recurrent T1 disease (6/8 studies, 75%) who were node-negative (5/8 studies, 63%). Partial breast re-irradiation was employed in a majority of studies (7/8 studies, 86%). The most common dose-fractionation schedule was 45 Gy in 30 twice-daily fractions (3/8 studies, 37%), followed by 50 Gy in 25 daily fractions (2/8 studies, 25%) and 45 Gy in 25 daily fractions (1/8 studies, 13%). Six out of eight studies (75%) treated patients using photons with 3D conformal RT, whereas two out of eight studies (25%) used electron therapy alone. At a median follow-up ranging from 1 to 15 years, the average local recurrence rate was 10%. Grade 3 or worse acute and late skin and soft tissue toxicities were 1% and 3% respectively. Only one study documented the incidence of