TRLS-13 CLINICAL CHARACTERISTICS AND OVERALL SURVIVAL OF PATIENTS WITH METASTATIC BREAST CANCER AND BRAIN METASTASES: A SINGLE CENTER RETROSPECTIVE COHORT STUDY

Abstract PURPOSE Approximately 30% of patients with metastatic breast cancer (MBC) develop brain metastases (BM). It is critical to better understand risk factors and survival outcomes. METHODS We identified patients with MBC and BM diagnosed between 1997-2024 at our institution. Review of medical records were completed to identify key demographic, clinical, and survival characteristics. RESULTS We identified 513 patients with MBC and BMs with the following subtypes: HR+/HER2- (n=184, 35.9%), HER2+ (n=197, 38.4%), and triple negative breast cancer (TNBC; n=126, 24.6%). Median real world overall survival (rwOS) from first BM to death was 21.6 months (interquartile range 9.3-45.1) with the longest median rwOS in patients with HER2+ disease (31.0 months) vs. patients with HR+/HER2- (21.6 months) or TNBC (12.8 months) (p<0.001). By date of BM diagnosis 1997-2014 vs. 2015-2024 (~50% of patients in each time period), patients with HER2+ and TNBC lived longer in the more modern cohort compared to prior years (HER2+: 41.2 vs. 26.2 months, p<0.001; TNBC: 14.9 vs. 7.0 months, p=0.02); there was no statistically significant difference for patients with HR+/HER2- disease (16.5 vs. 21.6, p=0.09). In multivariable analysis, HER2+ disease (HR 0.64 95% CI 0.51-0.82, p<0.001), BM surgical resection (HR 0.67, 95% CI 0.52-0.87, p=0.003), and BM diagnosis after 2015 (HR 0.78, CI 0.63-0.95, p=0.015) were associated with longer rwOS. TNBC (HR 1.46, CI 1.12-1.89, p=0.005), having 6-10 brain metastases at baseline (HR 1.64, CI 1.13-2.39, p=0.01), and development of LMD (HR 1.40 CI 1.11-1.79, p=0.006) were associated with shorter rwOS. CONCLUSION In a cohort of >500 patients with MBC and BM, median rwOS from the diagnosis of first BM to death was almost two years. Patients with HER2+ and TNBC MBC with BM had improved rwOS in a more modern cohort; this was not seen for HR+/HER2- patients, representing an area of ongoing unmet clinical need.