Sentinel Lymph Node Removal After Neoadjuvant Chemotherapy in Clinically Node-Negative Patients: When to Stop?

BACKGROUND: The maximum number of sentinel lymph nodes (SLN) to be resected to accurately stage the axilla in patients undergoing neoadjuvant chemotherapy (NAC) for the treatment of clinically node-negative (cN0) breast cancer has not been determined. We sought to determine the sequence of removal of the positive SLNs in this patient population. METHODS: All patients aged ≥ 18 years diagnosed with cN0 invasive breast cancer who received NAC and underwent SLN surgery at Mayo Clinic Rochester between September 2008 and September 2018 were identified. Univariate analysis was performed to compare factors associated with positive nodes and where the first positive node was in the sequence of removal of the SLNs. RESULTS: We identified 446 cancers among 440 patients with a median age of 51 (IQR: 43, 61) years. At surgery, 381 (85.4%) cancers were pathologically node (ypN) negative and 65 (14.6%) were pN + . The number of nodes removed was similar for both patients with ypN0 and ypN + disease, with a median number of SLNs removed of 2.0 (IQR: 2.0, 3.0). Of all patients with a positive node, the first positive node was most commonly the 1st node removed (75.4%), and was identified by the 3rd SLN removed in all cases. CONCLUSIONS: Among cN0 patients treated with NAC, if a positive SLN is present, it is most commonly identified as the 1st sentinel node removed by the surgeon, and was identified by the 3rd sentinel node in our series. This suggests that once 3 SLNs have been resected, removal of additional sentinel lymph nodes does not add diagnostic value.