Upfront stereotactic radiosurgery for brain metastases from triple-negative breast cancer.

e14014 Background: Triple-negative breast cancer (TNBC) is an aggressive subtype with high propensity of brain metastases (BM). Outcomes after upfront stereotactic radiosurgery (SRS) for BM from TNBC patients are not well defined. We evaluated outcomes and identified prognostic factors for such patients. Methods: We reviewed 57 consecutive patients treated with upfront SRS for BM from TNBC in May 2008–April 2018 at a large-volume cancer center. Endpoints were overall survival (OS) from BM diagnosis and freedom from BM progression (FFBMP) after initial SRS. BM progression was defined as local and/or distant brain failure (LBF or DBF) after initial SRS; LBF was radiographic progression of treated lesions, assessed by a neuroradiologist or treating physician excluding post-radiation changes or radiation necrosis. Kaplan-Meier and Cox proportional hazard regression analyses were used to estimate survival outcomes and identify prognostic factors. Results: In this cohort of 57 patients with a median age of 53 y (range 26–82) at BM diagnosis and follow-up time of 12.2 months (mo, range 0.8–97.5), median time to BM development from TNBC diagnosis was 23.7 mo (range 0.7‒271.1). Estimated median OS time from initial BM diagnosis was 13.1 mo (95% CI 8.0‒19.5). In univariate analysis, Karnofsky performance score (KPS) > 70 (p = 0.03), having < 3 BMs (p = 0.016) at BM diagnosis, and BM as first site of metastasis (p = 0.041) were associated with longer OS. On multivariate analysis, KPS ≤70 was associated with higher risk of death (HR 3.0, p = 0.03). Of 46 patients with imaging follow-up for FFBMP assessment, 29 (63%) developed BM progression after initial SRS with an estimated median FFBMP of 7.4 mo (95% CI 5.7–12.7). Median times to LBF and DBF were 10 mo (range 0.3–97) and 5.9 mo (range 0.3–90.8). Estimated cumulative LBF rate was 17.8% (95% CI 2%–31.1%) and DBF 61.1% (95% CI 40.8%–74.4%) at 12 mo. Number of BMs at BM diagnosis (≥3 vs < 3) was not associated with FFBMP (p = 0.7). Of the 29 patients with BM progression, 5 did not receive salvage radiation therapy (RT) and 24 received salvage RT (SRS, whole-brain radiation [WBRT], or both SRS+WBRT). Receipt of salvage RT was associated with longer survival (median 21.7 mo vs. 7.0 mo for no salvage RT, p < 0.0001) and did not differ by type of salvage RT (median OS 18.6 mo for WBRT; 26.2 mo for SRS+WBRT; 35.9 mo for SRS, p = 0.08). Conclusions: We reported a median OS of 13.1 mo and FFBMP of 7.4 mo in TNBC patients with good local control. Good KPS was independent prognostic factor for better OS. FFBMP did not differ by number of SRS-treated brain lesions ( < 3 vs ≥3). Further prospective studies of larger numbers of patients needed for more accurate comparisons of treatment types.