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Due to advancements in systemic treatment, the survival of breast cancer (BC) patients (pts) has improved, resulting in an increased incidence of brain metastases (BM). Treatment options for BM are limited and primarily consist of palliative surgery and/or radiotherapy (RT)
Our aim is to analyze survival time for BC pts treated with RT either alone or in combination with surgery, after first event of BM. Secondly, to evaluate prognostic impact of predefined factors.

Pts were identified retrospectively at a single institution and included if they were treated with RT for their first event of BM between Jan 2015 and June 2020.
Statistics included Kaplan-Meier analysis and Log-rank test to evaluate survival, and Chi-square tests to analyze impact of eventual prognostic factors. The study was approved by the institutional research board.

In total, 144 pts were identified, of whom 106 (73.6%) and 27 (18.8%) received whole brain RT (WBRT) and stereotactic radiosurgery (SRS), respectively. Eleven pts (7.6%) underwent surgery followed by WBRT or SRS. A total of 129 pts (89.6%) had extracranial metastatic disease at BM debut. Median overall survival (OS) was 6.1 months (mth). OS was shorter in the WBRT group (4.7 mth) than in the SRS (9.5 mth) and surgery group (20.1 mth). Meningeal carcinomatosis (MC) led to short OS (3.5 mth vs 7 mth for those without). OS depending on performance status (PS) 0, 1, 2 and 3-4 was 20.1, 7.2, 3.8 and 1.6 mth, respectively. OS for pts with 1, 2-3 or >3 brain metastases was 12.7, 6.3, and 5 mth, respectively. Three molecular subgroups were defined (ER+/HER2-, triple-negative, and HER2+ regardless ER) with corresponding OS 4.8, 7.4, and 12.7 mth. Pts in the ER+/HER2- group were older, had metastatic disease for a longer time at BM, poorer PS, and were more likely to develop MC. Pts with BM as first metastatic event had an OS of 20.1 mth, while pts who had received 1, 2-3 or >3 preceding treatment lines at BM debut had an OS of 4.9, 5.4, and 5.2 mth respectively.

Despite advancements in the treatment of metastatic breast cancer, BM is associated with a poor prognosis. PS, MC, metastatic burden, BC subtype, and number of systemic treatment lines before BM influenced survival. These factors should be considered when deciding treatment for pts with BM.