Impact of the American College of Surgeons Oncology Group Z0011 Randomized Trial on the Number of Axillary Nodes Removed for Patients with Early-Stage Breast Cancer

BackgroundThe Z0011 trial showed similar outcomes between sentinel node biopsy (SNB) alone and axillary node dissection (ALND) for early-stage breast cancer, but few studies have examined Z0011's impact on practice patterns.Study DesignUsing the National Cancer Data Base, we examined use of SNB alone in patients who did and did not fulfill Z0011 eligibility criteria from 1998 to 2011. Because the National Cancer Data Base does not specifically identify SNB vs ALND, we categorized removal of ≤4 nodes as SNB only and ≥10 nodes as ALND.ResultsOf 74,309 lumpectomy patients who fulfilled Z0011 criteria; 17,630 (23.7%) had a ≤4 nodes removed, 15,619 (21.0%) had 5 to 9 nodes removed, and 41,060 (55.3%) had ≥10 nodes removed. The proportion of lumpectomy patients receiving SNB increased from 6.1% in 1998 to 23.0% in 2009 to 56.0% in 2011 (p < 0.001). Independent predictors of ALND in lumpectomy patients were triple-negative tumors, younger than 50 years old, African-American race, size ≥3.0 cm, ≥2 positive nodes, invasive lobular carcinoma, grade III disease, and lymph node macrometastases. Patients outside of Z0011 criteria also underwent SNB alone: 54% of patients with tumors >5 cm, 52.5% who received no radiation therapy or accelerated partial breast irradiation, 35.9% with clinically positive nodes, 22.3% who underwent mastectomy, and 12.9% who had >3 tumor-positive nodes.ConclusionsThe use of SNB alone for patients fulfilling Z0011 criteria has increased substantially from 2009 to 2011. A considerable proportion of patients falling outside of Z0011 eligibility criteria were also treated with SNB alone.