Validation of the 21-Gene Recurrence Score Assay in Patients with Hormone Receptor-Positive, HER2-Negative Breast Cancer and 0 to 3 Positive Lymph Nodes: Risk Pattern and Outcomes on a Community Level.

Introduction: The aim of the present study was to analyze the performance of Oncotype DX® multigene assay (ODX®) in patients with 0-3 lymph nodes in a high-volume community hospital.
Methods: Patients with non-metastatic HR*/HER2- EBC and 0-3 positive lymph nodes, who underwent primary surgery at the Red Cross Hospital Munich, Germany and consecutively had ODX® testing were included in this retrospective study. The distribution of clinicopathologic characteristics, recurrence score (RS) risk, and use of systemic therapy were compared among patients without positive lymph nodes (N0) and patients with micrometastases or 1 to 3 positive lymph nodes (N1). Disease-free survival (DFS) and overall survival (OS) were estimated.
Results: From 2012 to 2017 ODX® was consecutively performed in 575 (16.4%) of 3,492 women with HR*/HER- EBC, of which 553 were eligible for this analysis (N0: 60.8%; N1: 39.2%). Among the patients included, 441 (79.7%) had an RS of 0 to 25 and 112 (20.3%) had an RS of 26 or higher. In patients with RS 0 to 25 the rate of chemotherapy use was low, independent from nodal status (N0: 17.1% and N1: 19.1%) and 5-year DFS was 90.5% and 91.7% for N0 and N1 patients, respectively. There was no significant difference in DFS (90.5% vs. 93.3%; p = 0.101) or OS (97.2% vs. 96.0%; p = 0.737) for patients with an RS of 0 to 25 when treated with chemo-endocrine therapy or endocrine therapy alone, independent from nodal status. Conclusions: The results of the study confirm the observations from randomized studies on the use of the ODX® in a real-world population in terms of risk distribution and patient outcome. Adjuvant chemotherapy could be safely omitted in patients with HR*/HER2- breast cancer with 0-3 positive lymph nodes and RS <25.