D. Zhao1,2, V. M. Khatri1,2, J. Y. Nakashima1,2, D. E. Oliver1, H. H. M. Yu1, M. Vogelbaum3, A. Etame3, H. S. Han4, H. Soliman4, M. N. Mills1, A. Soyano4, and K. A. Ahmed5; 1H. Lee Moffitt Cancer Center and Research Institute, Department of Radiation Oncology, Tampa, FL, 2University of South Florida, Tampa, FL, 3H. Lee Moffitt Cancer Center and Research Institute, Department of Neuro-Oncology, Tampa, FL, 4H. Lee Moffitt Cancer Center and Research Institute, Department of Breast Oncology, Tampa, FL, 5Department of Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL
Purpose/Objective(s): We investigated the clinical outcomes of breast cancer brain metastases (BCBMs) treated with stereotactic radiosurgery (SRS) with or without systemic metastasis. Materials/
Methods: We retrospectively reviewed patients who underwent SRS to BCBMs from 2005-2020 from a prospectively maintained database. Patients were stratified by BCBMs with or without systemic metastasis on the date of SRS. The Kaplan-Meier method was used to calculate overall survival (OS), central nervous system progression free survival (CNS-PFS), and distant intracranial control (DIC) from the date of SRS. Prognostic variables were assessed using the Cox proportional hazards model. Results: We identified 223 patients who underwent SRS to 819 BCBMs. Of the 223 patients, 179 (80%) had systemic metastasis with 722 BCBMs, while 44 (20%) had no systemic metastasis with 97 BCBMs on the date of SRS. No differences were noted in patients with or without systemic metastases with regards to histology (p=0.93), subtype (p=0.48), age (p=0.32), or Karnofsky Performance Status (KPS) (p=0.66). There was a trend towards patients without systemic metastases having fewer brain metastases (p=0.07) and undergoing surgical resection of brain metastases (p<0.0001). Median follow-up from the date of SRS was 76.4 months (range 1.3-131.0). In patients with or without systemic metastasis on the date of SRS, the median OS was 22 months (95% CI 18.3-25.66) and 38.1 months (95% CI 24.77-46.73) (p=0.01), respectively. The median CNS-PFS was 8.6 months (95% CI 7.83-10.37) and 13.0 months (95% CI 6.93-19.1) (p=0.078), respectively. The median DIC was 10.0 months (range 8.4-11.7) and 13.7 months (range 8.9-31.2) (p=0.03), respectively. On univariate analysis, absence of systemic metastasis on the date of SRS was associated with improved survival (HR 0.60, 95% CI 0.41-0.89, p=0.01). On multivariate analysis, the HER2 positive subtype was associated with improved survival (adjusted HR 1.9, 95% CI 1.04-3.29, p=0.04). Of the 44 patients who had no systemic metastasis on the date of SRS, 29 patients (66%) received systemic treatment after SRS including CDK 4/6 inhibitors (n=2; 7%), anti-PD-1 therapy (n=4; 14%), chemotherapy (n=7; 29%), HER2 targeted therapy (n=12; 41%), and endocrine therapy (n=8; 28%). A total of 14 of these 44 patients (31.8%) eventually developed systemic metastasis after SRS, most commonly to the bone (33%), liver (33%) and lung (27%). Conclusion: BCBMs without systemic metastasis is a rare presentation but after SRS these patients were noted to have improved OS and DIC. Further investigation into the biology of patients with brain only breast metastatic disease is warranted.
