The findings of this study indicate that, among patients with lymph node–negative, ER-positive/ERBB2-negative breast cancer from the STO-3 randomized clinical trial, tumor size followed by tumor grade were significantly associated with long-term risk of distant recurrence, as patients with larger tumors and higher tumor grades had significantly worse long-term survival compared to patients with smaller tumors and lower tumor grades. This evidence concerns the gene ERBB2 and neoplasm.