The Role of Oncotype DX^® Recurrence Score in Predicting Axillary Response After Neoadjuvant Chemotherapy in Breast Cancer

Introduction: Oncotype DX^® recurrence score (RS) is well-recognized for guiding decision making in adjuvant chemotherapy; however, the predictive capability of this genomic assay in determining axillary response to neoadjuvant chemotherapy (NCT) has not been established. Methods: Using the National Cancer Data Base (NCDB), we identified patients diagnosed with T1-T2, clinically N1/N2, estrogen receptor-positive/human epidermal growth factor receptor 2-negative (ER +/HER2 −) invasive ductal carcinoma of the breast between 2010 and 2015. Patients with an Oncotype DX^® RS who received NCT were included. RS was defined as low (< 18), intermediate (18–30), or high (> 30). Unadjusted and adjusted analyses were performed to determine the association between axillary pathologic complete response (pCR) and RS. Results: This study included a total of 158 women. RS was low in 56 (35.4%) patients, intermediate in 62 (39.2%) patients, and high in 40 (25.3%) patients. The majority of patients presented with clinical N1 disease (89.2%). Axillary pCR was achieved in 23 (14.6%) patients. When stratifying patients with axillary pCR by RS, 11 (47.8%) patients had a high RS, 6 (26.1%) patients had an intermediate RS, and 6 (26.1%) patients had a low RS. Comparing cohorts by RS, 27.5% of patients with high RS tumors had an axillary pCR, compared with only 9.7% in the intermediate RS group, and 10.7% in the low RS group (p = 0.0268). Conclusion: Our findings demonstrate that Oncotype DX^® RS is an independent predictor of axillary pCR in patients with ER +/HER2 − breast cancers receiving NCT. A greater proportion of patients with a high RS achieved axillary pCR. These results support Oncotype DX^® as a tool to improve clinical decision making in axillary management.