De-escalating axillary management after neoadjuvant chemotherapy in breast cancer: The ratio of positive sentinel lymph nodes matters

Background: De-escalation of axillary surgery in breast cancer (BC) patients diminishes sequelae without compromising cancer outcomes. Surgical management of the axilla is challenging after neoadjuvant treatment. We aimed to identify the factors associated with residual axillary disease amenable to lymphadenectomy in patients with positive sentinel lymph node biopsy (SLNB). Methods: We conducted a retrospective observational study in Hospital 12 de Octubre (Spain). We included BC patients with positive SLNB who underwent axillary dissection after neoadjuvant chemotherapy. Univariate and multivariate logistic regression models were performed to identify independent predictors of residual axillary disease. We estimated the ratio of positive nodes in SLNB and assessed the diagnostic validity of this ratio in relation to residual axillary disease. Results: We included 103 patients in the study. Residual axillary disease was identified in 54 patients (52.4%). Clinically node positive status at diagnosis (OR = 18.3, 95%CI: 4.0 -83.6) and a ratio of positive nodes in SLNB >= 0.5 (OR = 6.5, 95%CI 41.7 -23.7) were associated with residual axillary disease. The sensitivity and negative predictive value of a ratio of positive nodes in SLNB >= 0.5 were 87% (95%CI 75.1% -94.6%) and 75% (95%CI 55.1% -89.3%), respectively. Conclusions: In our study, for patients with positive SLNB after neoadjuvant chemotherapy, stage N + at diagnosis and a ratio of positive nodes in SLNB >= 0.5 were independent risk factors of positive residual axillary disease. This ratio is a feasible measure with a good diagnostic validity for residual axillary disease and could be used as a guiding factor in the surgical management of these patients.