Outcomes of changing systemic therapy in patients with relapsed breast cancer and 1 to 3 brain metastases.

The development of brain metastases (BMs) in breast cancer (BC) patients remains a challenging complication. Current clinical practice guidelines recommend local treatment of BMs without changing systemic therapy (CST) in patients with stable extracranial disease. We retrospectively investigated the impact of CST (when applicable as per treating physician's discretion) following the diagnosis and management of oligometastatic (1-3) BMs in patients without extracranial metastases on the progression-free survival time (PFS), and overall survival (OS). Hazard ratios (HRs) were calculated using the Cox proportional hazard model. Among the 2645 patients with BC and BMs treated between 2002 and 2015, 74 were included for analysis. 40.5% of patients had HER2 + disease. Median time from diagnosis of BC to BMs was 17.6 months. 54%, 8%, and 38% of BMs were managed by radiation, craniotomy, or combination, respectively. Following the primary management of BMs, we observed that CST occurred in 26 (35.5%) patients, consisting of initiation of therapy in 13.5% and switching of ongoing adjuvant therapy in 22%. Median PFS was 6.6 months among patients who had CST compared to 7.1 months in those who did not (HR = 0.88 [0.52-1.47], p = 0.62). Median OS was 20.1 months among patients who had CST compared to 15.1 months in those who did not (HR = 0.68 [0.40-1.16], p = 0.16). Upon the successful local management of oligometastatic BMs in patients without extracranial disease, we did not find a significant difference in survival between patients who experienced a change in systemic therapy as compared to those who did not.