Prediction of Distant Recurrence Using EndoPredict Among Women with ER+, HER2- Node-Positive and Node-Negative Breast Cancer Treated with Endocrine Therapy Only

Purpose: Prognostic molecular assays may aid in treatment decisions for women with estrogen receptor (ER)-positive, HER2-negative breast cancer. The prognostic value of a 12-gene expression assay (EndoPredict) was reevaluated in the combined ABCSG-6/8 cohorts with longer clinical follow-up. Experimental Design: EndoPredict (EP; molecular score, EPclin score) was evaluated in women with ER-positive, HER2-negative node-positive and node-negative breast cancer who received 5 years of endocrine therapy only (median follow-up, 9.6 years; N = 1,702). Distant recurrence-free rate (DRFR; 95% confidence interval) was assessed 10 and 15 years after diagnosis. Results: Overall, 62.6% of patients had low-risk EPclin scores with significantly improved DRFR relative to high-risk patients (HR, 4.77; 95% CI, 3.37-6.67; P < 0.0001). Ten-year DRFR (0-10 years) was improved among patients with lowrisk versus high-risk EPclin scores in the full cohort [95.5% (94.1%-97.0%) vs. 80.3% (76.9%-83.9%)] as well as for patients with node-negative disease [95.5% (94.0%-97.1%) vs. 87.0% (82.6%-91.7%)] or with 1 to 3 positive nodes [95.6% (92.2%-99.1%) vs. 80.9% (75.9%-86.1%)]. The molecular and EPclin scores were significant predictors of DRFR after adjusting for clinical variables, regardless of nodal status. Similar results were observed for late recurrence (5-15 years; HR, 4.52; 95% CI, 2.65-7.72; P < 0.0001). The EPclin score significantly added prognostic information to a late metastasis nomogram (CTS5 score; P < 0.001). Conclusions: This study demonstrates that EPclin can identify patients at low risk for early or late recurrence who may safely forgo adjuvant chemotherapy or extended endocrine therapy, respectively, regardless of nodal status.