Additional Axillary Disease After Neoadjuvant Chemotherapy for Patients with Clinically Node-Negative but Sentinel Node-Positive Disease

Background Axillary lymph node dissection (ALND) is associated with considerable risk of arm morbidity. This study aimed to identify risk factors for additional disease found at ALND in patients with a diagnosis of clinically node-negative (cN0) breast cancer who had sentinel lymph node (SLN) metastasis after neoadjuvant chemotherapy (NACT) as a help to identify patients for whom ALND may be safely omitted. Methods This retrospective national cohort study analyzed Danish patients with a diagnosis of cT1-3 breast cancer and cN0 disease from October 2016 to November 2022 but a positive SLN biopsy after NACT. Uni- and multivariable logistic regression analyses with stepwise backward elimination were performed to identify factors predictive of additional axillary disease at ALND. Results The study identified 346 patients eligible for analyses. Additional disease at ALND was found in 111 patients (32 %), but only 11 % of those with isolated tumor cells in the SLNs had additional axillary disease. It was respectively 22 % and 42 % for micro- and macrometastases. The final multivariable model identified the size of the metastatic deposit in the SLN, the ratio of positive SLNs, extracapsular extension, multifocality, and clinical T-stage as significant predictors of additional axillary disease. Conclusion Patients with isolated tumor cells in the sentinel nodes after NACT have a limited risk of additional axillary disease at ALND. However, other factors influence the probability and may be considered in an individualized approach.