Comparison of EndoPredict and EPclin With Oncotype DX Recurrence Score for Prediction of Risk of Distant Recurrence After Endocrine Therapy

BACKGROUND Estimating distant recurrence (DR) risk among women with estrogen receptor-positive (ER+), human epidermal growth factor receptor 2 (HER2)-negative early breast cancer helps decisions on using adjuvant chemotherapy. The 21-gene Oncotype DX recurrence score (RS) is widely used for this. EndoPredict (EPclin) is an alternative test combining prognostic information from an eight-gene signature (EP score) with tumor size and nodal status. We compared the prognostic information provided by RS and EPclin for 10-year DR risk. METHODS We used likelihood ratio χ² and Kaplan-Meier survival analyses to compare prognostic information provided by EP, EPclin, RS, and the clinical treatment score (CTS) of clinicopathologic parameters in 928 patients with ER+ disease treated with five years' anastrozole or tamoxifen. Comparisons were made for early (0-5 years) and late (5-10 years) DR according to nodal status. All statistical tests were two-sided. RESULTS In the overall population, EP and EPclin provided substantially more prognostic information than RS (LRχ(2): EP = 49.3; LRχ(2): EPclin = 139.3; LRχ(2): RS = 29.1), with greater differences in late DR and in node-positive patients. EP and EPclin remained statistically significantly prognostic when adjusted for RS (ΔLRχ(2): EP+RS vs RS = 20.2; ΔLRχ(2): EPclin+RS vs RS = 113.8). Using predefined cut-offs, EPclin and RS identified 58.8% and 61.7% patients as low risk, with hazard ratios for non-low vs low risk of 5.99 (95% confidence interval [CI] = 3.94 to 9.11) and 2.73 (95% CI = 1.91 to 3.89), respectively. CONCLUSIONS EP and EPclin were highly prognostic for DR in endocrine-treated patients with ER+, HER2-negative disease. EPclin provided more prognostic information than RS. This was partly but not entirely because of EPclin integrating molecular data with nodal status and tumor size.