Does Lymph Node Status Prior to Neoadjuvant Chemotherapy Influence the Number of Sentinel Nodes Removed?

Recent prospective trials support the use of sentinel lymph node biopsy (SLNB) in breast cancer patients after neoadjuvant chemotherapy (NAC) with a lower false-negative rate if three or more sentinel lymph nodes (SLNs) are identified. In this study, we investigated whether the pre-NAC axillary lymph node status influences the number of SLNs identified. Stage I-III breast cancer patients who received NAC and underwent SLNB from May 2014 to April 2016 were identified from an institutional prospective database. Clinical and pathological factors among clinically node-negative (cN-) and clinically node-positive (cN+) patients who converted to cN- post-NAC were compared. Generalized linear mixed models analyzed factors associated with the number of SLNs removed. Among 343 patients who underwent SLNB during the study period, 335 (98%) had at least one SLN identified, and subsequently comprised the study population. The median number of SLNs identified was 4 (range 1-14), which did not differ according to pre-NAC nodal status (P = 0.15). Overall, 85% of patients had three or more SLNs identified (80% cN- group vs. 89% cN+ group; P = 0.02). On univariable analysis, age < 50 years and presenting with a positive axillary node were significantly associated with identifying three or more SLNs. Our study confirms that SLNB was successfully performed in 98% of our patients after NAC, with very few failed mapping procedures. In the post-NAC setting, the median number of SLNs identified was four, and the status of the axilla prior to NAC did not negatively affect the number of SLNs identified.