The effect of Oncotype DX® on adjuvant chemotherapy treatment decisions in early breast cancer

Introduction The aim of this study was to objectively establish the value of the Oncotype DX® (ODX) gene assay in adjuvant treatment decisions for intermediate risk patients with early, oestrogen receptor positive, human epidermal growth factor receptor 2 negative, lymph node negative breast cancer at a district general hospital. Methods All patients who underwent surgery for breast cancer between January 2015 and December 2017 at Queen Elizabeth Hospital in King’s Lynn were considered for inclusion in the study. Those who did not meet the criteria for ODX referral were excluded. Patients were divided into two cohorts based on whether they were treated before or after the introduction of ODX testing in this hospital (June 2016): the pre-ODX and post-ODX groups. The primary outcome was the percentage of patients for whom adjuvant chemotherapy (AC) was recommended in each group. Results Of the 462 patients who underwent surgery during the study period, 43 met the eligibility criteria for ODX testing: 18 in the pre-ODX group and 25 in the post-ODX group. AC was recommended and given to 11 (61%) of the patients in the pre-ODX group. In the post-ODX group, AC was recommended for seven patients with an ODX Recurrence Score® (RS) of >25; this was given to six patients (24%). One patient (with a RS of 26) declined AC. ODX testing led to a significant reduction in the proportion of patients who received AC (p=0.015). Conclusions In intermediate risk patients with breast cancer, the results of the ODX gene assay may change the decision for adjuvant treatment. It represents a valuable tool to assist patients’ and clinicians’ decision making regarding adjuvant chemotherapy.