Utilization and outcomes of the 21-gene recurrence score in de novo metastatic breast cancer.

Background: Limited data exist regarding the utility and validity of the 21-gene recurrence score (RS) in patients with de novo metastatic breast cancer (dnMBC). This study aimed to investigate the practice patterns as well as associated survival outcomes based on 21-gene RS in dnMBC.
Research Design and Methods: The Surveillance, Epidemiology, and End Results Oncotype database was queried for women with hormone receptor-positive and Her2-negative dnMBC.
Results: A total of 153 patients were identified, including 62.7% and 37.3% of patients who had RS < 26 and ≥ 26, respectively. Patients with RS ≥ 26 were more likely to receive chemotherapy compared to those with RS < 26 (61.4% vs. 28.1%, p  < 0.001). Patients with RS ≥ 26 had an inferior breast cancer-specific survival (BCSS) (2-year BCSS: 84.3% vs. 89.5, p  = 0.067) and overall survival (OS) compared to those with RS < 26 (2-year OS: 76.9% vs. 87.4%, p  = 0.018). The multivariate Cox proportional hazard models showed that those with RS ≥ 26 had a significantly inferior BCSS (hazard ratio [HR] 2.251, 95% confidence interval [CI] 1.056-4.799, p  = 0.036) and OS (HR 2.151, 95%CI 1.123-4.120, p  = 0.021) compared to those with RS < 26.
Conclusions: The 21-gene RS assay is an important prognostic factor in patients with dnMBC.