The Predictive Value of Serum HER2/neu for Response to Anthracycline-Based and Trastuzumab-Based Neoadjuvant Chemotherapy

PURPOSE Little information exists about the possible influence of serum HER2/neu on response to chemotherapy. We propose that the assessment of serum HER2/neu in a pretreatment serum sample may be useful in predicting response to neoadjuvant chemotherapy. METHODS All breast cancer patients were tested by immunohistochemical stain and fluorescent in situ hybridization for HER2/neu before treatment. Serum HER2/neu was twice measured by chemiluminescence immunoassay (ADVIA Centaur System) before neoadjuvant chemotherapy and before operation. The cut-off value was 10.2 mg/mL, according to the previous study. Pathologic complete response (pCR) was considered as no residual tumor or remnant ductal carcinoma in situ; partial response (PR) was a less than 50% decrease in maximal diameter in pathologic tumor size. The measurements for the changes of serum HER2/neu were defined as pretreatment HER2/neu-preoperation HER2/neu. We compared the change of serum HER2/neu between that from before chemotherapy and that after chemotherapy, the pathologic complete response and partial response, and the trastuzumab group and anthracycline group. RESULTS Serum HER2/neu was decreased after neoadjuvant chemotherapy. The mean of serum HER2/neu in prechemotherapy was 15.4±9.0 ng/mL, and that of postchemotherapy was 10.5±2.0 ng/mL (p=0.04). Pathologic response was correlated with the change of serum HER2/neu (PR, 11.7±2.2 ng/mL vs. pCR, 23.7±13.1 ng/mL; p=0.01). In the trastuzumab group, pCR was marginally correlated with the change of serum HER2/neu (PR, 0.8±0.84 ng/mL vs. pCR, 21.1±13.2 ng/mL; p=0.08). CONCLUSION Serum HER2/neu levels during treatment were associated with pathologic response in patients receiving neoadjuvant chemotherapy, particularly, in a trastuzumab-based regimen. The change of serum HER2/neu levels may serve in monitoring neoadjuvant therapy in HER2/neu-overexpressed breast cancer.