Axillary pathologic response after neoadjuvant chemotherapy and surgery according to breast cancers subtypes and survival impact

e12595 Background: The rate of pathologic complete response in the axilla (pCRAx) according to breast cancer biologic subtypes and the impact of nodal response on survival are lacking. Methods: Inclusion criteria were all T-stage breast cancers with initial lymph node involvement (determined by clinical palpation and radiological assessment by ultrasound and/or 18F-FDG PET scan), non-metastatic, treated with neoadjuvant chemotherapy followed by surgery with axillary lymph node dissection, managed at the George-François Leclerc Cancer Center in Dijon, France, between 2000 and 2018. pCRAx was defined as the absence of invasive cells in the axillary lymph nodes ( i.e. ypN0). The Sataloff classification was used as reference on each pathological report. Patients with a Sataloff NA classification ( i.e. evidence of therapeutic effect, and no residual disease) were classified as having pCRAx. Univariate and multivariate analysis were performed to identify factors predictive of pCRAx. Then, we analysed recurrence-free survival (RFS) and overall survival (OS) according to the type of nodal response of the different tumor subtypes. Survival curves were constructed using the Kaplan Meier method and compared using the log rank test. Results: Among 437 patients included, 227 (52%) were pathologically proven node-positive disease by biopsy. pCRAx rate was 35% (n=153) but varied according to tumor subtypes: 69.4% in HR(Hormone Receptor)-/HER2-positive, 47.4% in HR-/HER2-negative, 46.7% in HR+/HER2-positive, 8.5% in HR+/HER2-negative. By multivariate analysis, the factors significantly associated with pCRAx were HER2-positive profile (OR 4.48 (2.14-9.65), p