Management of the axilla has arguably evolved more rapidly than any other area of breast surgery over the past 20 years. Sentinel lymph node (SLN) biopsy superseded axillary lymph node dissection (ALND) for staging the clinically negative axilla and was adopted as the standard of care in the early 2000s after several single-institution and multicenter trials demonstrated test equivalence of SLN biopsy to ALND for axillary staging among patients with early-stage disease.
Skepticism endured that patients with node-positive, clinically negative axillae could safely undergo SLN biopsy alone, recalling the outcome of the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-04 randomized trial from the 1970s in which half of the women with node-positive tumors who did not undergo ALND or axillary irradiation developed axillary recurrences at a median of 15 months after surgery. So when the American College of Surgeons Oncology Group Z0011 trial was published in 2011, showing that women with clinical T1-2N0 breast cancer undergoing breast-conserving therapy (BCT) with 1 to 2 positive SLNs could forego ALND without detriment to survival or locoregional recurrence risk, this initial report received criticism for inadequate follow-up (6 years).