Prospective evaluation of the feasibility of sentinel lymph node biopsy in breast cancer patients with negative axillary conversion after neoadjuvant chemotherapy

Purpose: Tumor response to neoadjuvant chemotherapy (NAC) may adversely affect the identification and accuracy rate of sentinel lymph node biopsy (SLNB). This study was conducted to evaluate the feasibility of SLNB in node-positive breast cancer patients with negative axillary conversion after NAC. Materials and Methods: Ninety-six patients with positive nodes at presentation were prospectively enrolled. ¹⁸Fluorodeoxyglucose-positron emission tomography (¹⁸F-FDG PET) and ultrasonography were performed before and after NAC. A metastatic axillary lymph node was defined as positive if it was positive upon both ¹⁸F-FDG PET and ultrasonography, while it was considered negative if it was negative upon both ¹⁸F-FDG PET and ultrasonography. Results: After NAC, 55 cases (57.3%) became clinically node-negative, while 41 cases (42.7%) remained node-positive. In the entire cohort, the sentinel lymph node (SLN) identification and false-negative rates were 84.3% (81/96) and 18.4% (9/49), respectively. In the negative axillary conversion group, the results of SLNB showed an 85.7% (48/55) identification rate and 16.7% (4/24) false-negative rate. Conclusion: For breast cancer patients with clinically positive nodes at presentation, it is difficult to conclude whether the SLN accurately represents the metastatic status of all axillary lymph nodes, even after clinically negative node conversion following NAC.