Omission of axillary lymph node dissection in patients with ypN+ breast cancer after neoadjuvant chemotherapy: A retrospective multicenter study (KROG 21-06).

Background: We evaluated the impact of omitting axillary lymph node dissection (ALND) on oncological outcomes in breast cancer patients with residual nodal disease after neoadjuvant chemotherapy (NAC).

Methods: The medical records of patients who underwent NAC followed by surgical resection and had residual nodal disease were retrospectively reviewed. In total, 1273 patients from 12 institutions were included; all underwent postoperative radiotherapy. Axillary surgery consisted of ALND in 1103 patients (86.6%) and sentinel lymph node biopsy (SLNBx) alone in 170 (13.4%). Univariate and multivariate analyses of disease-free survival (DFS) and overall survival (OS) were performed before and after propensity score matching (PSM).

Results: The median follow-up was 75.3 months (range, 2.5-182.7). Axillary recurrence rates were 4.8% in the ALND group (n = 53) and 4.7% in the SLNBx group (n = 8). Before PSM, univariate analysis indicated that the 5-year OS rate was inferior in the ALND group compared to the SLNBx group (86.6% vs. 93.3%, respectively; P = 0.002); multivariate analysis did not show a difference between groups (P = 0.325). After PSM, 258 and 136 patients were included in the ALND and SLNBx groups, respectively. There were no significant differences between the ALND and SLNBx groups in DFS (5-year rate, 75.8% vs. 76.9%, respectively; P = 0.406) or OS (5-year rate, 88.7% vs. 93.1%, respectively; P = 0.083).

Conclusions: SLNBx alone did not compromise oncological outcomes in patients with residual nodal disease after NAC. The omission of ALND might be a possible option for axillary management in patients treated with NAC and postoperative radiotherapy.