The effect of lymphatic tumor burden on sentinel lymph node biopsy results.

Increasing tumor burden in the axilla, as determined by the number of positive lymph nodes, adversely affects sentinel lymph node (SLN) identification and false-negative rates. The University of Louisville Breast Cancer Sentinel Lymph Node Study is a prospective, multi-institutional study. All enrolled patients underwent SLN biopsy, followed by complete level I/II axillary dissection. Participating surgeons represent a variety of practice settings, mostly community-based private practice. A total of 229 surgeons enrolled 2206 patients between August 1997 and November 2000. SLN biopsy was performed using blue dye injection alone, radioactive colloid alone, or a combination of the two agents. Two key parameters used to measure SLN biopsy success are the SLN identification rate and SLN false-negative rate. The overall SLN identification and false-negative rates were 92.5% and 8.0%, respectively. With increasing numbers of positive axillary nodes, there was a decreased sentinel node identification rate. There was no difference in the false-negative rate with increasing axillary tumor burden. Increased tumor burden in the axilla (as determined by the mean number of positive nodes) is associated with failure to identify a SLN in some cases, but is not an explanation for false-negative results. Standard axillary dissection should be performed when a SLN cannot be identified.