Impact of Neoadjuvant Versus Adjuvant Chemotherapy on the Extent of Axillary Surgery for Clinically Node-Negative Breast Cancers of Triple-Negative and HER2-Overexpressing Phenotypes.

Thompson, Jessica L; Wrubel, Erica; Davis, Alan T; Koehler, Tracy; Chung, Mathew H; Wright, G Paul

BACKGROUND Breast cancer patients with triple-negative or human epidermal growth factor receptor 2 (HER2)-overexpressing phenotypes are recommended to receive chemotherapy for primary tumors greater than 1 cm regardless of nodal status. Neoadjuvant chemotherapy may eradicate subclinical nodal metastases and reduce the extent of axillary surgery performed. PATIENTS AND METHODS A query of the National Cancer Database Participant User File was performed for new cases of female breast cancer from 2012 to 2015. Inclusion criteria were clinical N0 status, receipt of chemotherapy, and receipt of axillary surgery. Exclusions included hormone-positive/HER2-negative tumors and/or distant metastatic disease. Subjects were divided into groups by receipt of neoadjuvant or adjuvant chemotherapy. The primary end point was the extent of axillary surgery, defined as sentinel lymph node biopsy alone or axillary lymph node dissection (ALND). Subgroup analyses were performed on the basis of tumor phenotype and surgery of the primary site. RESULTS A total of 66,771 female patients were included, 15,967 of whom underwent neoadjuvant chemotherapy. ALND rates were higher in patients who received adjuvant chemotherapy (30.6% vs. 28.8%, P < .001). Among tumor phenotypes, the extent of axillary surgery was reduced most significantly for hormone-negative, HER2-positive disease (30.0% vs. 25.8%, P < .001). ALND rates were more substantially reduced for patients who underwent mastectomy (41.3% vs. 36.1%, P < .001) compared to partial mastectomy (21.8% vs. 20.1%, P = .002). Adjuvant chemotherapy was an independent predictor of ALND (odds ratio, 1.26; 95% confidence interval, 1.19-1.33). CONCLUSION Neoadjuvant chemotherapy reduces the extent of axillary surgery in clinically node-negative, nonluminal breast cancers.