Surgical Management of the Axilla in Clinically Node-Positive Patients Receiving Neoadjuvant Chemotherapy: A National Cancer Database Analysis.

BACKGROUND: The feasibility of sentinel lymph node biopsy (SLNB) in patients with clinically node-positive (cN+) disease who convert to clinically node-negative (cN0) disease following neoadjuvant chemotherapy (NAC) has been evaluated in several large clinical trials, but it remains unclear whether the approach has been broadly adopted in the United States. METHODS: The National Cancer Database was used to identify women diagnosed with cN+ breast cancer who received NAC followed by surgery between 2012 and 2015. Trends in axillary surgery were evaluated and multivariable logistic regression analyses performed to determine factors associated with receipt of SLNB. RESULTS: Of 12,965 women cN+ at baseline, the use of SLNB increased from 31.8% in 2012 to 49% in 2015 (p < 0.001). Using axillary pCR as a surrogate for patients who convert to cN0 following NAC, among 5127 (39.5%) ypN0 patients, SLNB increased from 38.2 to 58.4% over the study period (p < 0.001), resulting in avoidance of axillary dissection in 42.2% of ypN0 patients by 2015. In adjusted analyses, factors significantly associated with SLNB attempt included cN1 disease, age < 45 years, treatment facility type, triple-negative and HER2-positive subtypes, and year of diagnosis. In women with residual isolated tumor cells (ITCs), micrometastases, and ypN1 disease, SLNB was the only axillary procedure performed in 36.9%, 23.6%, and 13.0% of cases. CONCLUSIONS: The use of SLNB in cN+ patients receiving NAC increased significantly between 2012 and 2015. SLNB alone was performed in more than 10% of patients with ypN1 disease, 20% with micrometastases, and 35% with ITCs; the oncologic safety of omitting axillary dissection in these patients requires further evaluation.