Abstract PS15-10: Survival outcomes and prognosis for patients with triple negative breast cancer who received stereotactic radiosurgery for brain metastases
Authors: An Ran , Wang Yan , Wang Fuchenchu , Gao Chao , Raghavendra Akshara Singareeka , Amaya Diana , Ibrahim Nuhad K , Li Jing 
Published: February 2021

Abstract
Background: Triple-negative breast cancer (TNBC) has a high propensity for brain metastasis (BM) with poor prognosis. Stereotactic radiosurgery (SRS) has emerged as an effective treatment option for BM. However, clinical outcomes after SRS for BM from TNBC have not been well defined. We evaluated survival outcomes and prognostic factors among TNBC patients who received SRS for BMs.Methods: We retrospectively reviewed 99 patients with TNBC and BM who had received SRS at a single large-volume cancer center from May 2008 through April 2018. For the initial treatment of BM, 73 patients received SRS, 25 received whole-brain radiotherapy (WBRT), and 1 patient received surgery. Endpoints were overall survival (OS) from BM diagnosis, BM progression-free survival (BMPFS) from start of BM treatment, and times to intracranial local and distant failure from start of BM treatment. Both intracranial local and distant failure were considered BM progression. Local failure was defined as an increase in size of any treated lesions on imaging or assessment of treating physicians; enlargement attributable to radiation necrosis or post-radiation change was not counted as local failure. Kaplan-Meier analysis and Cox proportional hazard regression models were used to estimate survival curves and identify prognostic factors.Results: The median follow-up time from BM diagnosis was 12.7 months (95% confidence interval [CI] 1.3–52.1). The median age at BM diagnosis was 52 (range 24-82). The median interval between the diagnosis of primary breast cancer and BM was 25.8 months (95% CI 8.7–120.3). Of the 99 patients, 81 (81.8%) had 1-3 BMs and 18 (18.2%) had &gt;3 BMs at diagnosis. The median OS time for all patients was 13.3 months (95% CI 10.3–16.4), and the cumulative survival rates were 55.1% at 1 year and 29.2% at 2 years. Factors independently associated with increased risk of death in multivariate analysis were Karnofsky performance score (KPS) ≤70 (p=0.01) and uncontrolled extracranial metastasis at BM diagnosis (p=0.05). No difference was found in OS according to type of initial treatment for BMs. Of the initial 99 patients, 12 were excluded from the evaluation of BMPFS, local and distant failure for missing follow-up imaging after initial treatment. The median BMPFS time was 7.2 months (95% CI 5.1–9.3). Of the 87 evaluable patients, 23 (26.4%) developed local recurrence after initial treatment, and among these 10 of 61 patients (16.4%) had received SRS and 13 of 25 patients (52%) had received WBRT. Patients initially treated with SRS had longer time to local failure than WBRT (50th percentile not reached vs. median 14.0 months, p=0.001). Multivariate analysis showed higher risk of local failure for patients who initially received WBRT versus SRS (hazard ratio [HR] 3.4, p=0.005). Forty-nine of 87 patients (56.3%) developed distant brain recurrence after initial treatment, and among these 35 of 61 patients (57.4%) had received SRS and 14 of 25 patients (56%) had received WBRT. No difference in risk of distant brain failure was found for patients initially treated with SRS versus WBRT (p=0.24). No difference was found in time to develop distant failure after initial treatment with SRS (median 18.4 months) versus WBRT (median 12.8 months, p=0.24).Conclusion: Patients with BM from TNBC had a median OS time of 13.3 months and a BMPFS time of 7.2 months. KPS≤70 and uncontrolled extracranial disease at the time of BM diagnosis were independent prognostic factors that increase risk of death. Patients initially treated with SRS had a longer time to develop intracranial local failure than those initially given WBRT, and this may be related to patient selection. Further prospective studies of larger numbers of patients with BM from TNBC are needed for a more accurate comparison of treatment modalities.
Citation Format: Ran An, Yan Wang, Fuchenchu Wang, Chao Gao, Akshara Singareeka Raghavendra, Diana Amaya, Nuhad K Ibrahim, Jing Li. Survival outcomes and prognosis for patients with triple negative breast cancer who received stereotactic radiosurgery for brain metastases [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS15-10.