Predictive factors for omitting lymphadenectomy in patients with node‐positive breast cancer treated with neo‐adjuvant systemic therapy

A pathologic complete response (pCR) in the axilla occurs in 30%‐40% of patients with initially node‐positive breast cancer after neo‐adjuvant chemotherapy (NACT). Debate persists about whether to perform systematic axillary lymphadenectomy (ALND) in patients with initial node‐positive disease and clinical complete response after NACT. We aimed to identify predictive factors of axillary pCR (ypN0) after NACT. This retrospective study analyzed data for all patients with initial biopsy‐proven node‐positive disease who underwent ALND after NACT between June 2008 and December 2016 at our institution. Clinical and pathologic features, recurrence and specific mortality rates were compared between patients who achieved an axillary pCR and those who did not (ypN0 vs ypN+, respectively). A total of 331 patients were included, of whom 128 (38.7%) became ypN0 after NACT. Among patients with >2 suspicious axillary lymph nodes before treatment, 54 (38%) achieved ypN0 status. The independent predictors of ypN0 were Ki‐67 > 30 (OR 1.98; 95% CI, 1.146‐3.381), HER2 positivity (OR 2.6; 95% CI, 1.354‐5.108), nonluminal molecular‐like subtype (OR 4.15; 95% CI, 2.068‐5.108), and clinical complete response, defined as negative clinical and ultrasonographic findings (OR 2.8; 95% CI, 1.110‐7.081). After a mean follow‐up of 61 months, distant disease‐free and overall survival rates were higher in patients with ypN0 disease (HR 4.14; 95% CI, 2.03‐8.43) than ypN+ patients. Complete clinical response and the presence of nonluminal molecular‐like subtypes independently predicted ypN0. Patients meeting these criteria might be suitable form omitting ALND and just performing targeted axillary procedures to patients meeting these criteria.