Clinicopathological correlates, oncological impact, and validation of Oncotype DX™ in a European Tertiary Referral Centre.

ABSTRACT

Oncotype DX™ (ODX) score estimates prognosis and predicts breast cancer recurrence. It also individualizes patient adjuvant chemotherapy prescription in breast cancer. This assay relies on genetic and molecular markers; the clinicopathological phenotype of which are tested routinely. The aim of this study was determine whether clinicopathological and immunohistochemical information predicts ODX recurrence score (RS). Secondly, to assess the impact on adjuvant chemotherapy (AC) and oncological outcome of ODX testing in patients in a European tertiary referral center. Estrogen receptor positive (ER+), human epidermal growth factor receptor-2 negative (HER2-), lymph node negative (LN-), and female breast cancer patients with ODX testing performed between 2007 and 2015 were categorized into low- (<11), intermediate- (11-25), and high-risk (>25) groups. Clinicopathological and immunohistochemical correlates of RS were determined. Predictors of RS were assessed using binary logistic regression. Oncological outcome was assessed using Kaplan-Meier and Cox regression analyses. ODX was performed in 400 consecutive ER+LN- patients. Median follow-up was 74.1 months (3.0-144.4). Low grade (odds ratio [OR]2.39; 95% confidence interval [CI]1.04-5.51, p = 0.041) independently predicted low ODX, while high grade (OR2.04; 95% CI 1.19-3.49, p = 0.009) and reduced progesterone receptor (PgR) expression (OR 2.57, 95% CI 1.42-4.65, p = 0.002) independently predicted high ODX. Omission of AC in intermediate- (p = 0.159) and high-risk (p = 0.702) groups did not negatively impact survival. In conclusion, tumor grade independently predicts low and high RS, while PgR negativity predicts high RS. ODX reduced AC prescription without compromising oncological outcome.