Significance of sentinel lymph node micrometastases in human breast cancer.

BACKGROUND The significance of micrometastatic disease in the sentinel lymph nodes (SLN) of patients with invasive breast cancer has been questioned. The objective of our study was to review the impact of micrometastatic carcinoma detected by SLN biopsy. STUDY DESIGN Between January 1997 and May 2004, 2,408 patients with invasive breast cancer and an SLN with micrometastatic (N0[i+], N1mi) or no metastatic (N0[i-]) disease were identified through our breast database. Slide review was performed and reclassified by the 6(th) edition of the American Joint Committee on Cancer Staging Manual. Of these, 27 were excluded from analysis because of evidence of macrometastatic disease on slide review or enrollment in the American College of Surgeons Oncology Group Z10 study. RESULTS Of 2,381 patients, 2,108 were N0(i-), 151 were N0(i+), and 122 were N1mi. Overall and disease-free survivals of patients with an N1mi SLN were substantially worse than those in patients with an N0(i-) SLN (p < 0.001 and p=0.006, respectively). Additional positive non-SLNs were identified in 15.5% (15 of 97) of N1mi patients and 9.3% (10 of 107) of N0(i+) patients undergoing completion axillary lymph node dissection. Overall survival of the N0(i+) SLN patients not undergoing axillary dissection was substantially less than those undergoing axillary dissection (p=0.02). CONCLUSIONS Detection of micrometastatic carcinoma (N1mi) in the SLNs of invasive breast cancer patients is a major indicator of poorer survival compared with N0(i-) patients. Although survival of patients with an N0(i+) SLN does not statistically differ from that of N0(i-) patients, 9.3% of these patients had additional axillary nodal disease on axillary dissection, and N0(i+) patients had a decreased survival when axillary dissection was omitted.