The Xpert Breast Cancer Insight Test Predicts Distant Recurrence and Overall Survival in ER-Positive, HER2-Negative Early Breast Cancer

BACKGROUND: The aim of this study was to validate the Xpert Breast Cancer Insight (BC Insight) test. BC Insight is a multigene assay consisting of three target genes and three reference genes. MATERIALS AND METHODS: We studied the BC Insight test in 1278 formalin-fixed, paraffin-embedded surgical specimens from postmenopausal women with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative primary breast cancer with 0-3 involved lymph nodes. Time to distant recurrence (DR) and overall survival (OS) were analyzed using Cox models. RESULTS: The BC Insight test categorized 764 of 1089 (70.2%) evaluable patients as "low risk". The Xpert BC Insight Risk Score (XRS) was prognostic for DR (hazard ratio (HR) 1.93, 95% confidence interval (CI) 1.58 to 2.35, P<0.0001; C-index 0.73) and OS (HR 1.45, 95% CI 1.26 to 1.67, P<0.0001; C-index 0.65). At 10 years, 95.3% of Xpert BC Insight Risk Category (XRC) low-risk patients were metastasis-free and 89.6% were alive, compared with 85.6% and 77.1% of XRC high-risk patients, respectively (absolute DR risk difference 9.7%, P<0.0001; absolute risk of death difference 12.5%, P<0.0001). CONCLUSIONS: XRS and XRC are prognostic for DR in postmenopausal women with ER-positive, HER2-negative primary breast cancer. Furthermore, the BC Insight test accurately predicted OS in these patients, particularly in patients with 1-3 involved lymph nodes.