Micrometastases in axillary lymph nodes in breast cancer, post-neoadjuvant systemic therapy

Abstract Introduction: The significance of minimal residual axillary disease, specifically micrometastases, following neoadjuvant systemic therapy (NST) remains largely unexplored. Our study aimed to elucidate the prognostic implications of micrometastases in axillary and sentinel lymph nodes following NST. Methods This retrospective study analyzed primary breast cancer patients who underwent surgery after NST from September 2006 through February 2018. All patients received axillary lymph node dissection (ALND), either with or without sentinel lymph node biopsy. Recurrence-free survival (RFS)-associated variables were identified using a multivariate Cox proportional hazard model. Results Of the 978 patients examined, 438 (44.8%) exhibited no pathologic lymph node involvement (ypN0) after NST, while 89 (9.1%) had micrometastases (ypNmi). Multivariate analysis revealed no significant association between ypNmi and RFS in patients post-NST (hazard ratio [HR], 1.02; 95% confidence interval [CI], 0.42–2.49; P = 0.958). Notably, over half of the patients with sentinel lymph node micrometastases (SLNmi) had additional metastases, nearly triple that of SLN-negative patients (P < 0.001). Furthermore, SLNmi patients experienced significantly worse RFS compared to SLN-negative patients (HR, 2.23; 95% CI, 1.12–4.46; P = 0.023). Additional metastases in SLNmi were more prevalent in patients with larger residual breast disease greater than 20 mm, HR-positive/HER2-negative subtype, and low Ki-67 LI (< 14%). Conclusions While ypNmi does not influence the prognosis compared to ypN0, SLNmi emerges as a significant negative prognostic factor and a robust predictor of additional metastases. Hence, additional ALND may be warranted to confirm axillary nodal status in patients with SLNmi.