RADT-11. FACTORS ASSOCIATED WITH LOCAL FAILURE AFTER STEREOTACTIC RADIATION TO THE SURGICAL BED OF BREAST CANCER PATIENTS WITH A SINGLE BRAIN METASTASIS

Abstract BACKGROUND Metastatic breast cancer is the second most common cancer associated with brain metastases (BCBM). In our study we evaluated variables that influence local control in this breast cancer patients with a single BCBM who underwent surgical resection and stereotactic radiation to resection cavity. METHODS After ethics approval, we conducted a retrospective review of the medical records of BCBM patients treated with stereotactic radiation for BCBM between 2011 to 2022. Only breast cancer patients with a single BCBM who underwent surgical resection and stereotactic radiation to the surgical cavity were included. Clinical and dosimetric variables were analyzed to evaluate their impact on local control. Statistical analysis included descriptive analyses. X2 test was used for categorical variables. Total dose, dose per fraction, biologically effective dose (BED), and planning target volumes were analyzed as both continuous and categorical variables at different thresholds. A binary regression model was applied to study variables shown to impact local control. RESULTS A total of 62 patients included local control was 70.9% at 12 months. HER-2 disease, luminal-B, size of BCBM, time from craniotomy, total dose, inclusion of corridor, and non-cystic lesion were significant for local control. CONCLUSION Our data supports previous publications about the importance of tumor bed delineation, dose and fractionation, and time from craniotomy as factors associated with better local control. Our study shows that the role of BCBM subtype and new systemic therapies in contributing to local and intracranial control should be further explored.