The Role of the 21-Gene Recurrence Score in Breast Cancer Treatment.

Several multi-gene assays have been developed to predict the risk of recurrence in patients with estrogen receptor-positive early breast cancer and in whom endocrine therapy is planned. The 21-gene assay is widely used and its prognostic value has been retrospectively validated, showing significant differences in the risk of distant recurrence for patients at high versus low risk. Its role in predicting chemotherapy benefit has also been established, showing a clear benefit for high-risk patients and minimal benefit in those at low risk. These findings have been prospectively investigated in TAILORx (Trial Assigning Individualized Options for Treatment), where available data from the low-risk cohort confirms the prognostic value of this diagnostic test. The prognostic utility of the 21-gene assay increases when combined with clinicopathologic variables, and data from integrated models suggest that its use should be limited to patients with tumor characteristics suggestive of potential chemotherapy benefit. Furthermore, the 21-gene assay has been shown to impact clinical decision making in a cost-effective manner, although direct evidence of benefit from modified treatment recommendations is yet to be proven. The prognostic value of this test has also been shown in populations with node-positive or locally advanced disease treated with neoadjuvant chemotherapy, and ongoing trials aim to prospectively validate these findings.