Abstract P5-10-27: Incidence, risk factors and survival outcomes of Breast Cancer Brain Metastasis: a population-level SEER analysis

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Abstract Introduction: Metastasis is the leading cause of mortality in breast cancer (BC), and brain metastasis (BM) carries the most unfavorable prognosis. BMs are typically diagnosed based on symptoms, and the clinical outcomes varies depending on the number, location, and size. The aim of our study was to characterize the incidence of BM at the time of diagnosis and to identify the risk factors that are associated with a higher incidence of Breast Cancer Brain Metastasis (BCBM). Method: Patients diagnosed with BC from 2010 to 2020 were identified using the Surveillance, Epidemiology, and End Results (SEER) database. We summarized clinicodemographic data by BM status to identify potential risk factors for developing BM. Multivariate logistic regression was performed to determine the risk factors associated with BM at diagnosis. Survival outcomes by BM status were analyzed by using cox-proportional hazard regression for the overall population and adjusted for gender, age (18-40 years old (y), 41- 61 y, 61-80 y, and 81+ y), race, marital status, residential area, and treatment modalities. The analysis was done using R version 4.4.1 and statistical significance was defined at P< 0.05. Results: Of the 673,638 patients diagnosed with BC, 2,924 (0.4%) had BCBM. The majority were females (99%, n=2,891) and aged 41 y or older (93%, n=1429). 61% were White (n= 1,772), 16% Black (n= 459), 15% Hispanic (n= 447), 7.2% Asian (n=211) and 0.9% Native American (n=27). BC subtypes among BCBM were: 38% hormone receptor (HR) +/HER2 -, 15% HR+/HER2+, 11% HR-/HER2+, and 18% triple negative BC (TNBC). Other metastases sites included 64% bone, 44% lung and 31% liver. Several factors were found to be significantly associated with higher risks of developing BCBM on multivariate logistic regression analysis. The following factors were associated with increased risk of brain metastases: ages 41-61 y (OR 1.2, 95% CI: 1.1-1.4, P <0.01), Hispanic ethnicity (OR 1.2, 95% CI: 1.1-1.3, P<0.004), being single, widowed, or separated (OR 1.2, 95% CI: 1.1-1.3, P<0.001), AJCC stage T4 (OR 4.4, 95% CI: 3.7-5.1, P<0.001) and nodal status N1/2/3 (OR 2.1, 95% CI: 1.9-2.3, P<0.001), presence of bone metastases (OR 20.6, 95% CI: 18.8-22.6, P<0.001), and HR-/HER2+ (OR 3.1, 95% CI: 2.7-3.5, P<0.001) and TNBC subtypes (OR 3.0, 95% CI: 2.7-3.4, P< 0.001). Patients with BCBM had a shorter median disease specific survival (DSS) compared to patients without BM (13 months (mo) vs. not reached (NR) (HR=22.5, 95% CI: 21.5-23.5, P <0.001). Moreover, they had shorter median overall survival (OS) compared to patients without BM (9 mo vs. NR) (HR=15.0, 95% CI: 14.4-15.7, P <0.001). TNBC patients with BMs have the worst OS (5 mo vs NR) (HR= 2.10 95% CI: 2.07-2.14, P<0.001) and DSS (7mo vs NR) (HR =2.71, CI 2.65-2.77 P<0.001). OS and DSS are also shorter among Black patients, with a median of 8 mo vs NR (HR=1.26, 95% CI: 1.24-1.28, P < 0.001) and (10mo vs NR) (HR =1.27, CI 1.25-1.30 P<0.001) respectively. Conclusion: Our study shows that patients with HER2-positive and TNBC, Hispanic ethnicity, older age, higher stage T4, living without a partner, nodal and bone metastases are at higher risk of developing BCBM at the time of diagnosis. Prompt screening and higher care should be provided to the patients with these high-risk factors to identify brain metastases. More studies are required to establish risk criteria for brain MRI screening and even preventive intervention on high-risk patients to delay the development of brain metastases. Citation Format: Zunairah Shah, Malak Alharbi, Jayasree Krishnan, Kriti Ahuja, Guangwei Yuan, Kristopher Attwood, Arya Mariam Roy, Shipra Gandhi. Incidence, risk factors and survival outcomes of Breast Cancer Brain Metastasis: a population-level SEER analysis [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P5-10-27.

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