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

As survival of patients with breast cancer (BC) considerably improved, 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. 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. 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) positive/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). 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). The median time from recurrence to brain metastases was 12 months ( P = 0.216). In this BCBM cohort, the primary tumor subtypes were distributed as follows: HR+/HER2- (30.5%), HR-/HER2+ (25.4%), TNBC (25.1%), 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 survival following brain metastases (SFBM) vary across breast cancer subtypes. Timely imaging screening facilitates early diagnosis of brain metastases, thereby improving patient outcomes. Systemic therapy combined with local treatment based on molecular subtypes represents the optimal current treatment strategy.