Abstract
Background Neoadjuvant systemic therapy ( NAST ) can be used to treat breast cancer. Pathologic complete response ( pCR ) is a surrogate marker for improved survival. This study examined response in the breast and axilla to NAST and identified features associated with pCR . Methods Patients undergoing NAST and surgery between January 2012 and June 2016 by surgeons at Westmead Breast Cancer Institute were identified. Patients with inflammatory or metastatic disease were excluded. Data were analysed to identify factors predictive of pCR . Results Ninety‐one patients were identified. Mean age was 49 years. Forty‐one patients had axillary metastases identified prior to NAST . Eighty‐three patients received chemotherapy alone, six endocrine therapy alone and two had both. Thirty‐seven patients had mastectomy and 54 had breast‐conserving surgery. The overall breast pCR rate was 29% higher in patients with triple‐negative (50%) or HER2 ‐positive (39%) disease and lower in luminal disease (11.6%, P = 0.001). Forty percent of node‐positive patients became node negative. The only variable associated with pCR was tumour biology. Patients with HER2 ‐positive breast cancer were more likely to have axillary pCR than those with luminal cancer (odds ratio: 28, P = 0.00005). Conclusion pCR in either the breast or axilla was most likely to be achieved in patients with HER2 ‐positive or triple‐negative breast cancers. In patients with luminal cancers, the goal of NAST is best considered to facilitate surgical options rather than obtaining a pCR .