Background: Sentinel lymph node biopsy (SLNB) has become a standard for axillary staging for early breast cancer patients. Prior studies suggest that SLNB may be more sensitive for the identification of lymph node disease than axillary lymph node dissection (ALND). We hypothesized that SLNB use increases the incidence of node-positivity in early breast cancer patients compared to ALND. Furthermore, survival improves due to more accurate staging (stage migration).
Methods: Registry data from an NCI-designated cancer center was reviewed for breast cancer patients with T1 and T2 tumors for two 5-year periods: before (1993-1997) and after (2000-2004) SLNB implementation (1998). TNM staging was updated to conform to American Joint Committee on Cancer (AJCC) 2003 guidelines.
Results: There were no differences in tumor size or stage groupings between the two time periods (n = 316 and 577). There was a non-significant increase in the proportion of patients with lymph node involvement (32 vs. 27%; P = .16) after SLNB implementation; though a trend of increased incidence of single-node positive patients was observed (13 vs. 8%; P = .07). This was significant in patients with T1A/T1B tumors (10 vs. 3%; P = .04), though not seen in T1C or T2 tumors. Stage II survival improved in the later time period (P = .02).
Conclusions: The increase in single-node positivity after SLNB implementation supports the theory that SLNB is more sensitive than ALND. Improvements in survival are likely due to the stage migration of patients who would have been node-negative by ALND (but were found to be node-positive by SLNB) in addition to improvements in adjuvant therapy.