Clinicopathologic features and prognostic factors of breast cancer brain metastases patients based on molecular subtypes: A real-world retrospective analysis.

e13077 Background: The incidence of breast cancer brain metastases (BCBM) is increasing. Molecular subtypes of breast cancer are important evidences for the development of follow-up strategies and systemic therapy for patients with BCBM. The study aimed to analyze the clinicopathological characteristics and identify prognostic factors for BCBM based on molecular subtype. Methods: In order to conduct a more detailed study on the clinical characteristics of brain metastases about BC, we divided them into four molecular subtypes. The clinicopathological data from 295 patients were retrospectively evaluated. COX regression analysis was used to identify the independent risk factors affecting survival following brain metastases. Results: There were significant differences in histological grade ( P < 0.001) among the four different molecular subtypes. The pathological inconsistency rate was higher for hormone receptor (HR) postive / human epidermal growth factor receptor 2 (HER2) negative BCBM (30.0%). The molecular subtypes in BCBM patients showed the trend of HR+ transforming into HR- subtypes. When brain metastases occurred, there were statistical differences in extracranial organs metastases among different molecular subtypes of BCBM ( P = 0.017). HR+/HER2- BCBM was often accompanied by bone metastasis (66.7%), while TNBC brain metastases was often accompanied by lung metastasis (61.0%). More patients with HER2+ BC were diagnosed by imaging examination ( P = 0.042). The median disease-free survival (DFS) and brain metastases-free survival (BMFS) in all BCBM patients were 20 and 40 months (both P < 0.001). According to the ranking, BMFS was 65 months (HR+/HER2-), 44.5 months (HR+/HER2+), 31 months (HR-/HER2+), and 28 months (TNBC). The median time from recurrence to brain metastases was 12 months ( P = 0.216). The median SFBM in patients with different BC molecular subtypes was ranked as HR-/HER2+ (33 months), HR+/HER2+ (25 months), HR+/HER2- (13 months), and TNBC (7 months). Molecular subtype of BC, Karnofsky performance status (KPS) score, metastases of extracranial organs, leptomeningeal metastasis, location of brain metastases craniocerebral radiotherapy and systemic therapy were independent prognostic factors of survival following brain metastases (SFBM). Conclusions: The risk of brain metastasis among the four primary tumor subtypes is ranked as follows: HR-/HER2+ (25.4%), TNBC (25.1%), HR+/HER2+ (19.0%), and HR+/HER2+ (19.0%). During disease progression, two factors increase brain metastasis risk: pathological loss of HR expression or acquisition of HER2 expression, and the presence of extracranial organ metastases in different subtypes. Median BMFS and SFBM vary across breast cancer subtypes. Timely imaging screening facilitates early diagnosis of brain metastases, thereby improving patient outcomes.