Background: Sentinel lymph node biopsy (SLNB) is a more sensitive and accurate nodal staging procedure than axillary lymph node dissection (ALND). Because of increased pathologic evaluation in the sentinel node era, more nodal micrometastases (MIC) (> 0.2 mm to 2 mm) and isolated tumor cells (ITC; ≤ 0.2 mm) have been identified. We present the 10-year analysis of our prospective SLN study, focusing on regional axillary node status and distant metastases in patients with nodal ITC and MIC. Study Design: From 1996 to 2005, breast cancer patients were enrolled in an Institutional Review Board-approved, multicenter study. SLNs were examined at multiple levels by hematoxylin and eosin; most (85%) hematoxylin and eosin-negative SLNs were also examined by cytokeratin immunohistochemistry. Data from 1,259 patients with invasive breast cancer and in whom an SLN was found were reviewed for this analysis. Results: Of the 1,259 patients, 893 (71%) had negative SLNs, 25 (2%) had ITCs, 57 (5%) had MIC, and 284 (23%) had positive SLNs. None of the 13 patients with ITCs who underwent an ALND had additional positive nodes, compared with 27% (11 of 41) of patients with MIC. At a mean followup of 4.9 years, the distant recurrence rates for SLN-negative, ITC, MIC, and SLN-positive groups were 6%, 8%, 14%, and 21%, respectively. The presence of MIC in the SLN was associated with a significantly shorter disease-free interval than was SLN negativity (p < 0.02 by Cox regression model). Conclusions: This prospective breast cancer study found that sentinel node MIC, but not ITCs, were associated with additional positive nodes and with distant recurrence. These data suggest that ALND may be unnecessary in patients with ITCs. But ALND and more aggressive adjuvant therapy should be considered in patients with SLN micrometastases.
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