Analysis of the Clinical Molecular Characteristics and Neoadjuvant Chemotherapy Response in Patients with Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer and Axillary Lymph Node Metastasis

Objective: This study aimed to investigate the clinical molecular characteristics in patients with human epidermal growth factor receptor 2 (HER2)-negative breast cancer and axillary lymph node metastasis and explored the related factors of the neoadjuvant chemotherapy (NAC) response. Methods: The data of 185 patients with HER2-negative breast cancer and axillary lymph node metastasis who were treated in the Department of Breast Center of the Affiliated Hospital of Qingdao University from July 2017 to July 2021 were retrospectively analyzed. The clinical features and the related factors for the responses of the primary tumor and axillary lymph node metastasis to NAC were analyzed. Statistical analysis was conducted using the SPSS 26.0 statistical software. Univariate analysis was conducted using the chi(2) test, and multivariate analysis was conducted using logistic regression analysis. Results: The differences in estrogen receptor (ER), progesterone receptor (PR), and Ki67 among the three HER2-negative subgroups (the immunohistochemistry (IHC)0 group, IHC1+ group, and IHC2+/in situ hybridization- group) were statistically significant (p < 0.05). Univariate analysis revealed that the differences in the tumor stage, ER, PR, and Ki67 among the groups based on the response of the primary tumor to NAC were statistically significant (p< 0.05), and the differences in ER, PR, and Ki67 among the groups based on the response of axillary lymph node metastasis to NAC were statistically significant (p < 0.05). Multivariate analysis revealed that the difference in Ki67 among the groups based on the response of axillary lymph node metastasis to NAC was statistically significant (p < 0.05). Conclusions: When the expression level of HER2-negative IHC increases, the positive rates of ER and PR increase. A smaller tumor, negative ER, negative PR, and a Ki67 level >30% indicate a good effect of NAC for primary tumors. Negative ER, negative PR, and a Ki67 level >30% indicate a good effect of NAC for axillary lymph node metastasis. Therefore, Ki67 may be an independent factor affecting the efficacy of NAC for axillary lymph node metastasis.