Predicting breast and axillary response after neoadjuvant treatment for breast cancer: The role of histology vs receptor status.

ABSTRACT

PURPOSE: Neoadjuvant systemic treatment (NST) is increasingly administered in breast cancer patients. This study was conducted to identify predictors for tumor response in the breast and axilla. METHODS: All female patients with nonmetastatic, noninflammatory breast cancer receiving NST between 2003-2013 at the Catharina Cancer Institute in Eindhoven, The Netherlands, were included. RESULTS: The majority of 216 of the 337 patients receiving NST (65%) presented with a cT2 tumor. In 159 patients (47%), the axilla was clinically node positive. A pathologic complete response (pCR) in the breast was achieved in 83 patients (24.6%), and a pCR in the axilla in 65 node-positive patients (40.9%). The triple-negative (OR 4.29, 95% CI 2.15-8.55) and hormone receptor (HR)-negative/HER2-positive tumors (OR 3.73, 95% CI 1.59-8.75) were associated with in-breast pCR. Patients with invasive lobular carcinoma (ILC) were less likely to experience in-breast pCR (OR 0.10, 95% CI 0.01-0.73) than those with invasive ductal cancer. Axillary pCR was found in 65 clinically node-positive patients (41%). Axillary pCR was more likely to occur in HR-positive/HER2-positive (OR 6.24, 95% CI 1.86-20.90) and HR-negative/HER2-positive tumors (OR 6.41, 95% CI 1.95-21.06), compared to HER2-negative disease. In-breast pCR was strongly associated with axillary pCR (OR 10.89, 95% CI 4.20-28.22). CONCLUSION: Response to NST in the breast and axilla is largely determined by receptor status, with high pCR rates occurring in HER2-positive and triple-negative tumors. For axillary pCR, in-breast pCR and HER2-positive disease are the most important predictive factors.