Characterization of treatments and disease course for women with breast cancer brain metastases: Five-year retrospective single institution experience.
Authors: Chew Sonya , Carroll Hailey Kathryn , Darwish Waseem Mohammed Zaid , Higgins Michaela Jane , McCaffrey John , Kelly Catherine Margaret 
Published: June 2021

e13055 Background: Up to 30% of patients (pts) with breast cancer (BC) will develop brain metastases (BM) during the course of their disease. BM can have a devastating effect on independence and quality of life. The incidence of BM and overall survival (OS) differs according to BC subtype. We sought to characterise disease course, treatments and outcomes for our patient cohort with BM over the last 5 years. Methods: We extracted clinicopathological data using electronic records from Jan 2015 to Dec 2020 on BC subtype, time to BM development, type and number of therapies given for BM, and OS from BM diagnosis. Results were generated using SPSS Statistics v27. Results: We identified 99 pts. Median age was 49 (Interquartile range (IQR) 41 to 57). Of the BC subtypes; 41 (41.4%) were hormone receptor (HR)+/HER2-; 28 (28.2%) HR+/HER2+; 15 (15.2%) HR-/HER2+ and 15 (15.2%) were HR-/HER2-. 20% presented with de novo MBC (of which 4 had BM at presentation) and 80% had relapsed MBC. At first presentation with MBC (relapsed and de novo) 74% of pts had no brain metastases, 18% had BM with extracranial disease and 8% had BM only with no extracranial disease (5 had HER2+, 2 had HR-/HER2- and 1 had HR+/HER2-). HR-/HER2- pts had the highest incidence (40%) of presentation of BM at MBC diagnosis. Median time to BM development was 17 months (HR+/Her2-), 11 months (HR+/HER2+), 12 months (HR-/HER2+) and 3 months (HR-/HER2-). Almost half (46%) of pts had systemic treatment after developing BM. HR+Her2+ pts received the most treatment lines post BM development with a median of 2 lines (range 1-6). Almost 70% of pts (n=68) received local therapy for brain metastases with a median of 1 line of treatment (IQR 1-2). Whole brain radiotherapy (WBRT) (n=48, 70%) was the most frequently used modality followed by surgery (n=15, 23%) and stereotactic body radiotherapy (SBRT) (n=5, 7%). Patients with HER2+ BM had the highest incidence of receiving SBRT or surgery in the first line (33%). In pts who received WBRT alone (n=40) the median time to death post WBRT was 2.6 months, while in those who received surgery or SBRT (n=20) the median time to death was 15.5 months. Median OS from BM diagnosis was 4 months (HR+/HER2-), 10 months (HR+/HER2+), 8 months (HR-/HER2+), and 2 months (HR-/HER2-). For the 15 pts with HER2+ BC given TDM-1 after BM development 60% had a progression free survival of 1 year. 3 pts received palbociclib after BM in the first line and all died within 3 months. Conclusions: OS from BM diagnosis in our cohort is similar to international figures, with HR-/HER2- pts having the worst prognosis. Although our cohort is small, OS was >1 year for 60% of HER2+ pts who received TDM1 after BM development which is encouraging for antibody drug conjugates and CNS activity. OS was poor at less than 3 months for pts who received WBRT indicating higher burden of disease in the CNS and highlights an important question about whether it has a role in this setting.