Prognostic factors for patients with breast cancer brain metastasis after stereotactic radiotherapy.

e13109 Background: Breast cancer (BC) is the most common cancer in females and BC brain metastasis (BCBM) is considered as the second most frequent brain metastasis. Numerous prognostic factors are associated with survival for patients with BCBMs. Here we investigated the clinical factors associated with overall survival (OS) and distant intracranial control (DIC) after stereotactic radiotherapy (SRT) for BCBM. Methods: The records of BCBM patients treated with SRT were collected from electronic database in Cancer Center, Union Hospital, Tongji medical college, Huazhong University of Science and Technology Hospital. Based on the univariate and multivariate Cox regression analysis, the prognostic significance of available variables was assessed. The nomogram was created from Cox models and internally validated by use of bootstrap and cross-validation. Model discrimination was measured by calibration plots and the concordance index, and the clinical benefits were evaluated through clinical decision curve analysis (DCA). Results: 101 BCBM patients receiving SRT were analyzed in this study, and 5 patients were excluded with other primary malignancies or missing data. Median observation time was 15.0 months, and median OS was 22.0 months. OS rate was 71.5% in 1 year, 45.8% in 2 years, and 32.8% in 3 years. DIC was 49.8% in 1 year, 26.6% in 2 years, and 18.3% in 3 years. Multivariable analysis identified prognostic factors for OS including number of the brain metastasis, molecular subtypes type, brain metastasis as the first metastasis site, Karnofsky performance status (KPS), and receiving systemic therapy after SRT. KPS<80, triple-negative subtype, the existence of extracranial metastases, the existence of lung metastases were associated with decreased DIC. Selected by the Akaike information criterion (AIC), the nomogram model contains age, KPS, histological subtype, number of brain metastases, brain metastasis as first metastasis site, PTV size, liver metastases, albumin and neutrophils. The calibration curve for probability of survival showed high consistencies between prediction by nomogram and actual observation. The C-index of the nomogram for predicting survival was 0.823, and the bias-corrected C-index generated by bootstrap validation with 1,000 resamples was 0.772, which was statistically higher than the C-index values of the other systems: Recursive partitioning analysis (RPA) (0.627), Graded prognostic assessment (GPA) (0.637), Breast-specific Graded Prognostic Assessment (breast-GPA) (0.699). BCBM patients receiving SRT were divided into four risk groups: I group (risk score < 150), II group (150≤risk score< 220), III group (220≤risk score<290) and IV group (risk score≥290). The Kaplan‐Meier OS curves showed great discrimination among the four risk groups. Conclusions: The proposed nomogram resulted in a more-accurate prognostic prediction for BCBM patients receiving SRT.