Radiation Treatment Patterns for Breast Cancer Brain Metastases

Purpose: Breast cancer (BC) brain metastases (BM) treatment involves radiotherapy (RT), surgery, and CNS-penetrating systemic therapies. This study evaluated treatment patterns in brain RT and corresponding survival outcomes among patients with BC BM using the National Cancer Database (NCDB). Methods: Patients diagnosed with BC BM between 2010–2020 were identified. RT was categorized as whole brain (WBRT) vs. stereotactic (SRT). We fitted Overlap Propensity Score Weighting (OPSW) Cox models to account for confounders affecting OS. Variables included age, race, ethnicity, Charlson-Deyo score, insurance, molecular subtype, facility type, and systemic therapy. Results: Of 8,909 patients with BC BM, 43.4% received brain RT (74.1% WBRT, 25.9% SRS). Patients receiving RT tended to be younger, privately insured, triple-negative subtype, and received systemic therapy (all p < 0.001). There were no significant associations with race, ethnicity, education, or facility. However, patients that are African American, lower income, urban, triple-negative, or at community facilities were more likely to receive WBRT over SRS (p < 0.05). Median OS was 10.9 months (95% CI: 10.4–11.5). Systemic therapy alone (HR 0.40, 95% CI: 0.36–0.43) or combined with RT (HR 0.38, 95% CI: 0.35–0.42) improved OS, however RT alone did not improve survival on MVA (HR 0.96 (95% CI: 0.91–1.02). Among RT recipients, SRS was associated with improved OS vs. WBRT (HR 0.76, 95% CI: 0.69–0.83). Older age, comorbidities, lack of insurance, community facilities, and aggressive subtypes were associated with worse OS. Conclusions: Treatment patterns, particularly access to SRS, differ among BC BM patients. More prospective trials are needed to establish evidence-based treatment standards.