Systemic therapy for patients with breast cancer and one to three brain metastases (BM).

1090 Background: Despite advances in systemic therapies and improved overall survival of metastatic breast cancer (MBC) patients, the development of brain metastases (BMs) remains a challenging complication that affects quality of life and increases morbidity and mortality. Current clinical practice guidelines recommend local treatment of BMs without changing systemic therapy (CST) in patients with stable systemic disease. Methods: We retrospectively investigated the impact of CST (when applicable as per treating physician’s discretion) after diagnosis of the initial 1-3 BMs on the patient’s progression-free survival time (PFS), defined as time to death, to a second BMs or to extracranial metastases. All MBC patients with 1 to 3 BMs only (without extracranial disease) treated at our institution between 2002 and 2017 were identified. For each patient, full information on follow-up and administered therapies were mandatory for inclusion. Hazard ratios (HR) were calculated using the Cox proportional hazard model. We also computed the restricted mean survival time (RMST) up to 5 years of follow-up. Results: Among the 2645 patient with BM treated at our institution, 80 were included for analysis. In regards to primary BMs management in patients, 46 of 80 (57%) were treated by radiation therapy, 6 of 80 (7.5%) underwent surgical resection, and 28 of 80 (35%) were managed by a combination of surgery and radiation therapy. All patients had staging imaging documenting lack of extracranial metastases at the time of local therapy of BMs. Following the primary management of BM, we observed that providers changed systemic therapy in 32 of 80 (40%), defined as the CST group. CST included both initiation of therapy in 16 of 80 (20%) and switching of adjuvant therapy in 16 of 80 (20%). Median PFS among CST was 7.7 months vs. 7.2 months among no CST (HR = 0.855, 95% confidence interval (CI) 0.53-1.38, p = 0.52). 5-year RMST for the CST group was 16.6 months vs. 12.8 months in no CST group. The difference of 3.8 months (95% CI 4.3-11.8) was not statistically significant. Conclusions: Patients with 1-3 BMs without extracranial disease had a median PFS close to 7.5 months after local therapy. Consistent with current standard of care of maintaining the same systemic therapy approach upon developing isolated BMs, our findings did not demonstrate a significant difference in PFS between patients who experienced a change in systemic therapy compared to those who did not.