RADT-06. IMPACT OF STATUS OF TUMOR PROGRESSION PRIOR TO STEREOTACTIC RADIOSURGERY ON LOCAL TUMOR CONTROL IN PATIENTS WITH TRIPLE-NEGATIVE BREAST CANCER BRAIN METASTASES TREATED WITH STEREOTACTIC RADIOSURGERY

Abstract

Abstract INTRODUCTION Prognosis in patients triple-negative breast cancer (TNBC) brain metastases remains poor owing to the lack of treatment targeting pathways. Furthermore, approaches–like surgical resection, stereotactic radiosurgery (SRS), and whole-brain radiation therapy–have variable efficacy depending on the degree of tumor burden. The cohort of patients benefit least to targeted therapy and immunotherapy, therefore, forming ideal candidates to evaluate the local tumor control attributed to SRS. This study aimed to characterize intracranial tumor response and clinical outcomes in the patient cohort. PATIENTS and METHODS This retrospective, single-center study included patients with confirmed TNBC brain metastases treated with SRS at the University of Virginia Health. Tumor response, new intracranial tumor development, and survival were investigated. 24 patients with 169 total treated lesions between 2007 and 2021 were assessed. The median age of patients at the initial treatment was 49.1 years. RESULTS One MRI within one month prior to SRS plus the treatment study MRI were evaluated. Tumor progression at the time of SRS led to worse local tumor control following the first SRS treatment (p < 0.0001). 15.1% of total treated lesions demonstrated a complete response, while 48.5% had a partial response. 25.7% of lesions remained stable and 13.5% progressed. Three patients did not have any follow-up imaging to assess initial tumor response due to mortality. For patients with tumor progression, the progression-free survival was 4.93 months. Additionally, new intracranial metastases developed in ten patients over their treatment course. Median overall survival following the first SRS session was 9.83 months (range 0.9 - 37.7 months), with a 1-year and 2-year survival of 54.5% and 22.7%, respectively. CONCLUSION Tumor control in patients with TNBC treated with SRS is unfavorable. Tumor progression prior to SRS might lead to worse tumor control. Further study is warranted to evaluate this phenomenon in a large cohort of patients.