Abstract
PURPOSE: We examined distant brain failure (DBF) outcomes among patients treated with SRS for breast cancer brain metastases. METHODS: We completed a retrospective IRB-approved review of 75 breast cancer patients treated with SRS for 271 brain metastases. Median time to DBF was defined as time from initial SRS to MRI revealing a new lesion. Kaplan-Meier and Cox proportional hazards model were used for statistical evaluation. Of the 75 patients, 74 patients were classified with ER status (46 positive vs 28 negative), PR status (31 positive vs. 43 negative), and HER2-Neu status (35 positive vs. 39 negative). 43 patients (57%) had uncontrolled extracranial disease at time of initial SRS. 18 patients (24%) received prior WBRT and 5 patients (7%) received concurrent WBRT. RESULTS: The median time to development of 1 brain metastasis was 7 months, with 7 patients (9%) developing only 1 additional brain metastasis and 40 patients (53%) developing greater than 1 additional brain metastasis. Median time to development of 2–4 brain metastases was 15 months, with 10 patients (13%) developing only 2–4 additional brain metastases and 30 patients (40%) developing greater than 4 additional brain metastases. Median time to development of greater than 4 brain metastases was 22 months. Median time to leptomeningeal disease was not reached, with 19 patients (25%) developing LMD. PR positivity predicted for greater time to development of 1 new brain metastasis (p=0.025). Extracranial disease control was a positive prognostic factor for time to development of 1 new brain metastasis (p=0.046), 2–4 new brain metastases (p=0.004), and greater than 4 new brain metastases (p=0.004). CONCLUSION: Our results suggest nearly 2/3 of breast cancer patients treated with SRS for brain metastases will develop at least one additional metastasis. Prognostic factors for DBF for these patients include PR status and extracranial disease control.