Outcome prediction values of soluble human epidermal growth factor receptor-2 extracellular domain in metastatic breast cancer.

HER-2 overexpression is an independent predictor for poor prognosis of breast cancer patients. Recently, extracellular domain of HER-2 (ECD) was found detectable in the serum of breast cancer patients. In this prospective study, we wonder whether ECD levels predict the clinical outcome of metastatic breast cancer patients.ECD were measured in 190 women with metastatic breast cancer. Chi-square test was performed to determine the relationship between ECD status and clinical outcomes. Kaplan-Meier curves were applied for survival analysis.Elevated ECD levels were significantly associated with short-term response to Herceptin treatment. The median PFS was significantly longer in ECD-Low patients. The patients who remained low ECD levels or achieved low ECD levels after treatments have significantly longer PFS than those whose levels remained high or converted from low to high.Overall, our results support the clinical utility of measuring serum HER2 ECD levels in patients with advanced breast cancer. Baseline and serial measurements of serum ECD levels are reliably predictive of clinical outcome of breast cancer patients.