Abstract
BACKGROUND: To assess the impact of the 21-gene recurrence score (RS) on chemotherapy decision making and survival outcomes for breast cancer patients with >4 positive lymph nodes. METHODS: Patients with non-metastatic estrogen receptor-positive breast cancer with >4 positive lymph nodes diagnosed between 2004 and 2013 were identified using the Surveillance, Epidemiology, and End Results database. The relationships between the 21-gene RS value and survival outcomes, chemotherapy decision-making, and chemotherapy benefit were analyzed. RESULTS: A total of 410 patients were identified, including 191 (46.6%), 164 (40.0%), and 55 (13.4%) in the low-, intermediate-, and high-risk RS groups, respectively. The 21-gene RS assay results were independently related to chemotherapy receipt. A total of 59.0%, 68.0%, and 78.0% of patients received chemotherapy in the low-, intermediate-, and high-risk RS groups, respectively. The 21-gene RS was an independent indicator of breast cancer specific survival (BCSS) and overall survival (OS). Intermediate-risk [BCSS: hazards ratio (HR), 2.832, 95% confidence interval (CI): 1.160-6.910, P=0.022; OS: HR, 3.704, 95% CI: 1.750-7.836, P=0.001] and high-risk RS (BCSS: HR, 6.440, 95% CI: 2.597-15.974, P<0.001; OS: HR, 5.053, 95% CI: 2.199-11.608, P<0.001) cohorts had significantly lower survival outcomes compared to low-risk RS cohort. The 5-year BCSS were 92.7%, 88.3%, and 70.7% in patients in the low-, intermediate-, and high-risk RS cohorts, respectively (P<0.001), and the 5-year OS were 92.1%, 80.6%, and 66.6%, respectively (P<0.001). CONCLUSIONS: The 21-gene RS is an independent predictor of chemotherapy receipt and survival outcomes for breast cancer patients with > 4 positive lymph nodes.