The addition of adjuvant chemotherapy to hormonal therapy is recommended for patients with estrogen receptor-positive (ER+), node-positive (N+) early breast cancer (EBC). Some of these patients, however, are not likely to benefit from treatment and may, therefore, be overtreated while also incurring unnecessary treatment-related adverse events and health care costs. The 21-gene Recurrence Score assay has been clinically validated and recommended for use in patients with ER+, node-negative (N0) EBC to assess the 10-year risk of distant disease recurrence and predict the likelihood of response to adjuvant chemotherapy. A growing body of evidence from several large phase III clinical trials reports similar findings in patients with ER+, N+ EBC. A systematic review of published literature from key clinical trials that have used the 21-gene breast cancer assay in patients with ER+, N+ EBC was performed. The Recurrence Score has been shown to be an independent predictor of disease-free survival, overall survival, and distant recurrence-free interval in patients with ER+, N+ EBC. Outcomes from decision impact and health economics studies further indicate that the Recurrence Score affects physician treatment recommendations equally in patients with N+ or N0 disease. It also indicates that a reduction in Recurrence Score-directed chemotherapy is cost-effective. There is a large body of evidence to support the use of the 21-gene assay Recurrence Score in patients with N+ EBC. Use of this assay could help guide treatment decisions for patients who are most likely to receive benefit from chemotherapy.