ESTRO 2025 - Abstract Book

S612

Clinical - Breast

ESTRO 2025

Cancers: Long-Term Results of the SABR-COMET Phase II Randomized Trial. J Clin Oncol. 2020 Sep 1;38(25):2830 2838. 2.Plichta JK, Thomas SM, Hayes DF, Chavez-MacGregor M, Allison K, de Los Santos J, Fowler AM, Giuliano AE, Sharma P, Smith BD, van Eycken E, Edge SB, Hortobagyi GN. Novel Prognostic Staging System for Patients With De Novo Metastatic Breast Cancer. J Clin Oncol. 2023 May 10;41(14):2546-2560.

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Digital Poster Can stereotactic radiotherapy successfully treat brain metastases in breast cancer patients without the further need for whole brain radiotherapy? Donata Gräupner 1 , Marcin Kubeczko 2 , Justyna Rembak-Szynkiewicz 3 , Roland Kulik 4 , Elżbieta Nowicka 1 , Dorota Gabryś 5 1 III Department of Radiotherapy and Chemotherapy, Maria Sklodowska - Curie National Research Institute of Oncology, Gliwice Branch, Gliwice, Poland. 2 Breast Cancer Center, Maria Sklodowska - Curie National Research Institute of Oncology, Gliwice Branch, Gliwice, Poland. 3 Radiology and Diagnostic Imaging Department, Maria Sklodowska - Curie National Research Institute of Oncology, Gliwice Branch, Gliwice, Poland. 4 Radiotherapy Planning Department, Maria Sklodowska - Curie National Research Institute of Oncology, Gliwice Branch, Gliwice, Poland. 5 Radiotherapy Department, Radiotherapy Department, Gliwice, Poland Purpose/Objective: In breast cancer patients with brain metastases, we can offer stereotactic radiotherapy (SRT). We assessed the effectiveness of such treatment and the lack of further need for whole brain irradiation (WBRT). Material/Methods: In our retrospective analysis we selected breast cancer patients who were treated in our center between 2015 and 2023 for brain metastases with SRT without WBRT or brain metastasectomy. We selected a group of 49 patients, most of whom were treated for the presence of 1-5 metastatic lesions (84%). Total doses ranged from 12 Gy to 32 Gy delivered in 1-5 fractions. Results: Disease limited to brain was observed in 18% of patients, oligometastatic disease accounted for 22%. The median overall survival (OS) was 22.1 months, 2-year OS was 45.9% [95%CI 30.7-59.8%], while 3-year OS was 43.0% [95%CI 28.0-57.2%]. The median local control of primary irradiated volume (LC) was 18.2 months, 1-year LC was 66.3% [95%CI 46.8-80.1%], 2-year LC was 36.4% [95%CI 18.4-54.7%]. A trend toward longer LC was observed in patients with single metastasis, compared to higher number (p=0.16). The median volume of brain metastastes was 5.0 cm 3 (IQR 2.1-14.0). There was no difference in LC between total volume of metastases up to 5.0 cm 3 vs. larger (p=0.36), but there was an insignificant trend indicating longer LC in patients with a total metastasis volume of ≤1 cm³ compared to those with larger volumes (p=0.20). The median progression free survival within brain (PFS) was 9.6 months, 1-year PFS was 41.1% [95%CI 25.3-56.3%], while 2-year PFS was 11.8% (95%CI 3.3-26.1%). A longer brain PFS was observed in patients with single brain metastasis, compared to higher number of metastases (p=0.016). Breast cancer subtype, oligometastatic disease, metastases limited to brian, and symptomatic disease were not significantly associated with OS, LC, PFS. Majority 65% of patients had disease progression within brain, of these patients 44% received only repeated SRT, 12% required SRT but in longer follow up also WBRT, 28% were treated with WBRT after first SRT, 16% had fast progression within brain and were not retreated. The median time to WBRT was 10.8 months [IQR 5.6-26.8 months]. In 3 patients a total of 4 SRT were performed in the CNS, without the need of WBRT.

Conclusion: The use of stereotactic radiotherapy in the treatment of brain metastases in breast cancer patients allows for