Any patient with negative nodes with a central- or inner-quadrant primary was eligible for the French and EORTC trials, whereas only node-negative patients with high-risk features were eligible for the Canadian trial (tumor ≥5 cm, tumor ≥2 cm with ≤10 axillary nodes removed, estrogen receptor (ER) negative, histologic grade 3, or lymphovascular invasion present). The gene discussed is ESR1; the disease is neoplasm.