Significance of Residual Nodal Disease in Clinically Node-Negative Breast Cancer After Neoadjuvant Chemotherapy

Background: Trials evaluating omission of axillary dissection (ALND) in patients with cN0 breast cancer with positive sentinel lymph nodes (SLNs) have excluded neoadjuvant chemotherapy (NACT). It remains unclear whether the data can be extrapolated to cN0 patients undergoing NACT. This study sought to identify factors associated with positive SLNs and additional disease on ALND in cT1-2N0 disease after NACT.

Methods: The authors queried their database for cT1-2N0 patients treated with NACT followed by SLN biopsy from 1996 to 2022. Physical examination and ultrasound determined clinical nodal status. Multivariable logistic regression identified factors associated with positive SLNs and disease on ALND.

Results: Of 1930 patients, 234 (12.1%) had positive SLNs. Positive SLNs were predicted by hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) status (odds ratio [OR] 2.5; p < 0.0001), lobular histology (OR 1.8; p = 0.007), multifocality (OR 2; p = 0.001), grade 1 tumors (OR 2.5; p = 0.002), and cT2 category (OR 1.9; p = 0.004). Of the 234 patients with positive SLNs and known SLN metastasis size, 148 (63.2%) underwent ALND, and 39 (26.4%) had additional positive nodes. Increasing patient age predicted disease on ALND (OR 1.03; p = 0.02). No additional positive nodes on ALND were identified in patients with only isolated tumor cells compared with 12.3% who had micrometastases and 37.6% who had macrometastases (p = 0.01). During a 5-year median follow-up period of the SLN-positive patients, three (1.3%) experienced axillary recurrence and two of the three underwent ALND at the initial surgery with no additional positive nodes.

Conclusions: In cT1-2N0 breast cancer, HR+/HER2- status, lobular histology, multifocality and cT2 category predicted positive SLNs after NACT. Older age predicted positive nodes on ALND. Patients with positive SLNs had low axillary recurrence rates. These findings support investigation into omission of ALND in cN0 breast cancer and a low volume of SLN disease after NACT.