In Brief:
The American College of Surgeons Oncology Group Z0010 trial enrolled women with clinical T1,2N0 breast cancer planned for lumpectomy and sentinel lymph node (SLN) dissection followed by whole breast irradiation. Patients with hematoxylin and eosin–negative SLNs had no axillary-specific treatment. At 8.4 years, median follow-up, local-regional recurrences were rare and were associated with hormone receptor-negative disease and lymphovascular invasion.