Implications of the 21-gene recurrence score assay (Oncotype DX) on adjuvant treatment decisions in ER-positive early-stage breast cancer patients: experience of Kuwait Cancer Control Center

Abstract

Background: The Oncotype DX is a quantitative assay of the expression of 16 tumor-related genes and 5 reference genes that predicts the potential of adjuvant chemotherapy benefit in estrogen receptor (ER)-positive early breast cancer patients. The study aims to evaluate the impact of Oncotype DX as a tool for adjuvant treatment decision of ER-positive, HER2-negative, N0/N1 early-stage breast cancer patients and to determine which clinicopathological criteria derived the greatest advantage. Results: A hundred patients at a median age of 50 years were included. TNM stage distribution was 34, 63, and 3 patients for stages I, II, and IIIA respectively. Fifty-four patients had luminal A and 46 had luminal B tumors. The recurrence score (RS) results were low, intermediate, and high risk in 54, 34, and 12 patients respectively. Before the test results, adjuvant chemoendocrine therapy (CET) was recommended for 46 patients while 54 were advised for endocrine therapy (ET). After getting the test results, 25 patients received CET (1, 12, and12 patients in the low-, intermediate-, and high-risk groups respectively) and 75 received ET. Treatment change was documented in 37 patients (8 patients from ET to CET and 29 from CET to ET; p = 0.001, McNemar test). Treatment change was significant among patients ≤ 50 years, luminal B tumors, stage II and IIIA disease, and node-positive disease. Conclusion: Oncotype DX testing resulted in significant changes in the adjuvant treatment decisions in ER-positive, HER2-negative early breast cancer particularly in the case of young, luminal B, N1, and stage II–IIIA disease.