Treatment response correlation between primary tumor and axillary lymph nodes after neoadjuvant therapy in breast cancer: a retrospective study based on real-world data.

Background Excellent response of the primary tumor after neoadjuvant therapy may indicate a better axillary status in breast cancer. However, this treatment response correlation has not been investigated in Chinese breast cancer patients. Methods Patients diagnosed with breast cancer and treated with neoadjuvant therapy were included in this retrospective study, conducted at a comprehensive breast cancer institution in China. Clinicopathological factors at baseline were analyzed by univariate and multivariate analyses. Furthermore, association rules analyses were used to investigate the correlation between the pathologic response of the primary tumor and that of the axillary lymph nodes based on such factors. Results Multivariate logistic regression analysis showed that breast pathologic response was influenced by tumor size, classification of regional lymph nodes, histological grade, progesterone receptor status, and Ki67 expression. The potential influencing factor for the pathologic response of the axilla was found to be regional lymph node classification. The findings from association rules analyses demonstrated that when a pathologic complete response (pCR) in the breast was achieved among patients with cT2N0 and hormone receptor-negative disease, the axilla response in these patients was also highly likely to be pCR (the likelihood for axilla pCR was more than 90%). However, cT3N1-2 patients hardly achieved pCR for both the primary tumor and axillary lymph nodes (mean confidence, 0.9637). The clinicopathological factors accounting for the inconsistent response between the breast and the axilla were found to be hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative, and low Ki67 expression. Conclusions Our findings suggest a strong correlation between breast pCR and axilla pCR among patients with specific characteristics. These findings provide a basis for the selection of candidates for clinical trials on the omission of axillary surgery.