Monitoring Value of Serum HER2 as a Predictive Biomarker in Patients with Metastatic Breast Cancer

PURPOSE: The aim of this study was to investigate the monitoring value of serum HER2 in patients with metastatic breast cancer. PATIENTS AND METHODS: We firstly evaluated the association of serum HER2 levels with tissue HER2 expression and imaging results in 420 breast cancer patients admitted into Tianjin Medical University Cancer Institute and Hospital between April 2016 and December 2018. Secondly, we analyzed serum HER2 levels in breast cancer patients with different metastatic degrees. RESULTS: There is a higher correlation between serum HER2 and tissue HER2 in breast cancer patients with stage III (κ=0.670, p<0.001) and stage IV (κ=0.464, p<0.001). Serum HER2 levels were significantly associated with imaging results (κ=0.478, p<0.001). The ROC curve analysis showed that serum HER2 was superior to other serum markers for predicting metastatic breast cancer. Multinomial logistic regression revealed that the patients with higher serum HER2 levels would be more likely to have breast cancer metastasis. CONCLUSION: Serum HER2 levels in breast cancer patients can partly reflect tissue HER2 expression and tumor imaging changes, and serum HER2 may be used as a biomarker for evaluating metastatic status in patients with breast cancer.