ESTRO 2025 - Abstract Book

S625

Clinical - Breast

ESTRO 2025

4337

Digital Poster Mind the Gap: Examining Disparities in Adherence to the Danish Breast Cancer Group Radiotherapy Guidelines for Breast Cancer patients Bjarke Godske Baisner 1,2 , Louise Wichmann Matthiessen 3 , Maja V. Maraldo 4,5 , Else Maae 6 , Mette H. Nielsen 7 , Mette Møller 8 , Sami Al-Rawi 9 , Susanne Oksbjerg Dalton 10,11,12 , Cai Grau 13,14 , Birgitte Vrou Offersen 15,13,16 1 Department of Experimental Clinical Oncology, Aarhus University Hospital,, Aarhus, Denmark. 2 Department of clinical medicine, Aarhus University, Aarhus, Denmark. 3 Department of Oncology, Copenhagen University Hospital Herlev and Gentofte, Copenhagen, Denmark. 4 Department of Oncology, Copenhagen University Hospital, Copenhagen, Denmark. 5 Department of clinical medicin, University of clinical medicine, Copenhagen, Denmark. 6 Department of Oncology, Vejle Hospital, University of southern Denmark, Vejle, Denmark. 7 Department of Oncology, Odense University Hospital, Odense, Denmark. 8 Department of Oncology, Aalborg University Hospital, Aalborg, Denmark. 9 Department of oncology, Næstved Hospital, Næstved, Denmark. 10 The Danish Cancer Institute, The Danish Cancer Institute, Copenhagen, Denmark. 11 : Institute of Clinical Medicine, Faculty of Health, Copenhagen University, Copenhagen, Denmark. 12 Department of Clinical Oncology and Palliative Care, Zealand University Hospital, Næstved, Denmark. 13 Department of Clinical Medicine, Aarhus University, Aarhus, Denmark. 14 Danish Center for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark. 15 Department of Experimental Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark. 16 Department of Oncology, Aarhus University Hospital, Aarhus, Denmark Objectives : Breast cancer is the most common cancer among Danish women, with approximately 5000 cases annually (1). Advances in screening, surgery, systemic therapy, and radiotherapy have improved 5-year survival rates to around 85% for high-risk patients (2-4). Adjuvant radiotherapy, standard for patients following breast-conservation or with large tumours and/or nodal involvement, reduces local, regional, and distant recurrence, enhancing survival (2-7). Radiotherapy for breast cancer patients adheres to Danish Breast Cancer Group (DBCG) guidelines developed by the DBCG Radiotherapy Committee based on clinical research (8-10). The DBCG Quality Indicator (QI) report attracts substantial political attention when comparing cancer therapy across Denmark. The report reveals substantial deviations in radiotherapy provision, with some departments treating nearly all eligible patients, while others treat around 85%. This study seeks to understand why radiotherapy is not uniformly provided to all eligible patients across Denmark. The hypothesis is that reasons for deviations can be systematically categorised by the DBCG Radiotherapy Committee to refine future guideline adherence reporting. Methods : Using DBCG QI reports from 2020–2022 individual non-irradiated cases, where the patient had an indication for radiotherapy, were evaluated. Patient records were reviewed to document individual reasons for non-adherence to DBCG radiotherapy guidelines, comparing them with reasons reported to the DBCG database. Results: Overall, during the study period, 8624 patients were recommended radiotherapy according to DBCG guidelines, and 7682 patients (89%) had radiotherapy. The rates of non-irradiation varied (85%-93%) between the six radiotherapy departments. A key reason for omitting radiotherapy was mostly patient preferences (33%). A large group did not receive radiotherapy as part of the DBCG Natural trial (testing omission of radiotherapy) (27%), or the patient did have radiotherapy, but it was not correctly registered in the DBCG database (11%). Some patients had repeated surgery ending with mastectomy and thereby no need for radiotherapy, but it was registered in the DBCG database as breast conservation with need for radiation (7%). Remaining reasons were comorbidity (6%), shared decision making (3%), the physician’s decision (4%), intraoperative radiotherapy (2%), other reasons (2%) and disseminated disease prior to radiotherapy (1%). Importantly, all patients being eligible for radiotherapy but not treated with radiation had discussed the omission of therapy in at least one meeting with a physician. No patient was identified, where the omission of radiotherapy was due to a mistake.