Abstract
PURPOSE: We sought to evaluate the use of the Onco type DX Breast Cancer Assay for identifying candidates for adjuvant therapy in patients with estrogen receptor (ER)-positive, node-negative primary Stage I or IIA breast cancer. METHODS: A retrospective case-control study was conducted on 40 patients who underwent surgery between 2000 and 2008. Cases (n = 10) were patients who had metastases after surgery. Controls (n = 30) were patients who did not develop metastases and were individually matched to their case with respect to age. All patients were analyzed with regard to age, tumor size, histological grade, HER2 status, and the values of Recurrence Score (RS), ER score and PgR score generated by Onco type DX. We also divided the patients into low, intermediate or high-risk groups according to individual RS values. RESULTS: RS, risk category and histological grade were associated with metastases in patients with ER-positive, node-negative Stage I or IIA breast cancer. However, ER status, tumor size and PgR status were not associated with metastases. Histological grade was associated with RS value and the distribution pattern of risk category (P < 0.001 for each). CONCLUSIONS: Both histological grade and risk-category classification were effective in identifying women at risk of developing distant metastases after initial therapy for ER-positive, node-negative Stage I or IIA breast cancer. These patients may benefit from the addition of adjuvant therapy at diagnosis.