Breast Cancer Subtype is Associated With Axillary Lymph Node Metastasis: A Retrospective Cohort Study

The purpose of this study was to assess whether breast cancer subtype (BCS) as determined by estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 can predict the axillary lymph node metastasis in breast cancer. Patients who received breast conserving surgery or mastectomy and axillary lymph node dissection were identified from 2 cancer centers. The associations between clinicopathological variables and axillary lymph node involvement were evaluated in univariate and multivariate regression analyses. A total of 3471 patients met the inclusion criteria, and 53.0% had axillary lymph node metastases at diagnosis. Patients with hormone receptor (HR)-/human epidermal growth factor receptor 2 (HER2)- subtype had a higher grade disease and the lowest rate of lymphovascular invasion. Univariate and multivariable logistic regression analyses showed that BCS was significantly associated with lymph node involvement. Patients with the HR-/HER2- subtype had the lowest odds of having nodal positivity than those with other BCSs. HR+/HER2- (odds ratio [OR] 1.651, 95% confidence interval [CI]: 1.349-2.021, P < 0.001), HR+/HER2+ (OR 1.958, 95%CI 1.542-2.486, P < 0.001), and HR-/HER2+ (OR 1.525, 95%CI 1.181-1.970, P < 0.001) tumors had higher risk of nodal positivity than the HR-/HER2- subtype. The other independent predictors of nodal metastases included tumor size, tumor grade, and lymphovascular invasion. Breast cancer subtype can predict the presence of axillary lymph node metastasis in breast cancer. HR-/HER2- is associated with a reduced risk of axillary lymph node metastasis compared to other BCSs. Our findings may play an important role in guiding axillary treatment considerations if further confirmed in larger sample size studies.