Poorvu PD, Gelber SI, Rosenberg SM, et al. - Given the prognostic utility of the 21-gene recurrence score (RS) assay in women with early-stage estrogen receptor–positive (ER+) and human epidermal growth factor receptor 2–negative (HER2−) breast cancer, as well as its use to inform suggestions for chemotherapy, researchers analyzed a prospective cohort (Young Women's Breast Cancer Study) of 1,302 women diagnosed with breast cancer at age ≤ 40 years, given women ≤ 40 years of age signify a minority of patients examined using gene expression profiles. They selected patients with stage I-III ER+/HER2− breast cancer and performed RS assay on banked specimens for patients who had not been examined clinically. They found that prognostication of young women with node-negative and limited node-positive breast cancer was enabled by the RS assay, and it is a valuable tool for risk stratification. Findings revealed very good disease outcomes at a median follow-up of 6 years in young women with N0 disease and an RS of 0-25, a minority of whom were treated with chemotherapy, and node-positive disease with an RS < 11, whereas substantial risk of early distant recurrence was observed in those with N0 disease and an RS ≥ 26 or N1 disease with an RS ≥ 11.