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The prognostic and predictive role of 21‐gene recurrence scores in hormone receptor‐positive early‐stage breast cancer

Over the past two decades, gene expression profiling of breast cancer has emerged as an important tool in early‐stage breast cancer management. The approach provides important information on underlying biological mechanisms, breast cancer classification, future risk potential of developing recurrent metastatic disease, and provides beneficial clues for adjuvant chemotherapy in hormone receptor (HR) positive breast cancer. Of the commercially available genomic tests for breast cancer, the prognostic and predictive value of 21‐gene recurrence score tests have been validated using both retrospective data and prospective clinical trials. In this paper, we reviewed the current evidence on 21‐gene expression profiles for HR‐positive HER2‐negative early‐stage breast cancer management. We show that current evidence supports endocrine therapy alone as an appropriate adjuvant systemic therapy for approximately 70% of women with HR‐positive, HER2‐negative, node‐negative breast cancer. Evolving evidence also suggests that 21‐gene recurrence scores have predictive values for node‐positive breast cancer and that chemotherapy can be avoided in more than half of women with nodes 1 to 3 positive HR‐positive breast cancer. Furthermore, retrospective data also supports the predictive role of 21‐gene recurrence scores for adjuvant radiation therapy. A prospective trial in this area is ongoing.