S271
Clinical - Breast
ESTRO 2026
illustrate temporal treatment trends since 2016. A subgroup including women with left-sided tumours treated in January 2023 to September 2024 was selected to illustrate details in volumes and in doses. The latter was divided into three groups: ≤ 40 years, 41-50 years, and >50 years with age-group-specific fractionation schedules as recommended by the national care programme for breast cancer. Descriptive statistics, including number of patients, target and heart volumes and mean absorbed doses, are given with mean±standard deviation (SD) and median with inter quartile range (IQR). Results: By 2025, there were 12355 breast tumour cases reported into SKvaRT. Over time, the most common fractionation schedule changed from 50Gy@2Gy/fx and 42.6Gy@2.67Gy/fx in 2016 (delivered to 39% and 52% of patients, respectively) to the favouring of 40Gy@2.67Gy/fx peaking in 2021 (delivered to 83% of patients; Figure 1). Since 2022, 26Gy@5.2Gy/fx became increasingly common and is today delivered to 62% of patients. In the selected subgroup of left-sided tumours, there were 73 women ≤ 40 years, 109 women aged 41-50 years, and 1867 women >50 years (Table 1). VOI:s were in general numerically smaller for women ≤ 50 years. Dose variations within each fractionation schedule were small, indicated by structure SD<3.7 Gy and IQR<5.0 Gy.
after RT. As illustrated in Table 2, intra-fraction displacement of PTV was minimal. Coherently, duty cycle of treatment delivery through CMM gating was high (>90% in 97% of fractions).
Conclusion: to the best of our knowledge, this is the first report of APBI delivered as adaptive RT adopting a daily ATS workflow and gating through CMM. Treatment was feasible, with acceptable time on the table and a fair toxicity profile. Intra-fraction displacement of PTV was minimal, suggesting the potential to reduce CTV-PTV margins. Keywords: MR-linac, APBI, adaptive Poster Discussion 2300 Breast cancer research potential of the new Swedish national quality registry for radiotherapy Caroline E Olsson 1,2 , Magnus G Karlsson 3 , David B Norman 4 , Josef A Lundman 3 , Dan Lundstedt 5 1 Medical Radiation Science, Clinical Sciences/Sahlgrenska Academy/Gothenburg University, Gothenburg, Sweden. 2 Regional Cancer Center West, Västra Götalandsregionen, Gothenburg, Sweden. 3 Diagnostics and Intervention, Umeå University, Umeå, Sweden. 4 Regional Cancer Center North, Region Västerbotten, Umeå, Sweden. 5 Oncology, Clinical Sciences/Sahlgrenska Academy/Gothenburg University, Gothenburg, Sweden Purpose/Objective: The Swedish national quality registry for radiotherapy (RT; In Swedish:Svenska Kvalitetsregistret för RadioTerapi [SKvaRT]) was launched in 2023 and stores information on delivered treatments for all cancer diagnoses since 2026. Its primary purpose is to highlight temporal variations in RT, improve adherence to national treatment guidelines, and provide data for healthcare development, quality monitoring, clinical audit, and research. The aim of this study is to investigate to what extent SKvaRT data reflects temporal treatment trends for breast cancer. Other objectives are to compare volumes of interest (VOI) and related RT doses for selected breast cancer subgroups. Material/Methods: All patients with breast tumours (ICD codes C50 and D05) with curative treatment intent reported into SKvaRT by August 15th 2025 were identified to
Conclusion: This study demonstrates promising results for SKvaRT breast cancer data both in illustrating temporal treatment trends and variations in structure data. The
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