467 Predictors of Treatment Response and Overall Survival in Patients With Breast Cancer Brain Metastases Treated With Stereotactic Radiosurgery: A Prospective Study Using the NeuroPoint Alliance SRS Registry

INTRODUCTION: The role of stereotactic radiosurgery (SRS) in the management of breast cancer brain metastases is primarily supported by single-institution studies and interventional trials. METHODS: The Stereotactic Radiosurgery Quality Registry of the NeuroPoint Alliance (NPA) was employed for this study. The SRS NPA registry conducts prospective enrollment of patients undergoing SRS at 16 participating sites from 2017–2023. RESULTS: A total of 138 patients were identified, with a mean age of 59.8 years and a female proportion of 92.0%. The median overall survival was 17.9 months, and independent predictors of all-cause mortality included KPS = 90(HR = 6.25) and diabetes mellitus(HR = 7.23). The median time-to-local progression was 19.8 months. More than two lesions at baseline(HR = 9.27) and margin dose = 17.6 Gy(HR = 19.0) were predictive of local recurrence. The median out-of-field progression was not reached. Statistically significant predictors of out-of-field progression included margin dose = 17.6 Gy(HR = 14.6) and = 5 lesions at baseline(HR = 6.8). Intracranial progression-free survival was driven by local progression, with a median of 8.9 months, and predictors included =5 lesions at the time of SRS(HR = 6.0) and a margin dose =17.6 Gy(HR = 5.35). At final follow-up 17.1% of the patients experienced no change in EQ-5D, 34.3% demonstrated improvement, 11.4% displayed mixed results, and the remaining 37.1% worsened. On linear regression, pre-SRS surgical resection(r = 1.29) and baseline EQ-5D(r = 1.92) were statistically significant predictors of EQ-5D at final follow-up. CONCLUSIONS: Real-world data from the SRS NPA Registry demonstrated that the number of lesions at the time of SRS and margin dose were independent risk factors for local recurrence, out-of-field progression, and overall intracranial progression. Pre-SRS resection and baseline EQ-5D were independent predictors of quality-of-life following SRS.