Abstract PD13-05: Clinical-pathological patterns and prognosis of young women with breast cancer brain metastases: a single-centre retrospective study

Abstract Background: Breast cancer (BC) is the most frequent cancer among women and the second leading cause of central nervous system (CNS) metastases. Given limited data regarding the impact of young age on outcomes of women with metastatic breast cancer (MBC) and CNS metastases, we compared the clinical-pathological features, treatment patterns and outcomes of women ≤40 and those ≥40 years-of-age with CNS metastases in an established single-centre retrospective cohort. Methods: Patients with MBC and CNS metastases who were treated with surgery, whole-brain radiotherapy (WBRT), or stereotactic radiosurgery (SRS) at the Sunnybrook Odette Cancer Centre, Toronto, Canada between 2008 and 2018 were included. Clinical data was abstracted from electronic medical records. Patient characteristics were described with medians and interquartile ranges for continuous variables and percentages for categorical variables. Categorical variables were compared between young (<40 years of age) and older patients (≥40 years of age) using Chi-square tests and continuous variables using Wilcoxon rank-sum tests. Univariable and multivariable Cox proportional hazards models for brain-specific progression-free survival (bs-PFS) and overall survival (OS) were also generated with pre-specified variables of interest. Results: In total, 683 patients were included, of whom 7.5% (n=51) were <40 years of age and 92.5% (n=632) were ≥40 years of age at the time of CNS metastases. Similar characteristics were observed among young and older women with CNS metastases, with no statistically significant difference in BC subtype, tumour histology, and/or median time from MBC diagnosis to development of CNS metastases. Most patients in each age group had neurological symptoms at the time of initial presentation with CNS metastases (<40 years: 67.9% vs. ≥ 40 years: 77.8%, p = 0.24). However, we found that young women were significantly more likely to develop LMD than older women (39.6% vs. 22.3%, p= 0.004). In addition, young women were significantly more likely to be re-treated for CNS metastases (43.4% vs 24.5%, p=0.003). There was no significant difference in median bs-PFS (log-rank p = 0.35) or OS (log-rank p value = 0.52) between young and older women with MBC and CNS metastases (Table). Conclusions: In our study of women with MBC and CNS metastases who were <40 years of age were more likely to develop LMD than women ≥40 years of age. Although young women were also more likely to be re-treated for progression of CNS metastases, their bs-PFS and OS were not inferior that of patients ≥ 40 years-of-age. Citation Format: I. Kojundzic, J. Fritz, B. Id Said, H. Soliman, S. Vuong, M. Ennis, E. Warner, K. J. Jerzak. Clinical-pathological patterns and prognosis of young women with breast cancer brain metastases: a single-centre retrospective study [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PD13-05.