BACKGROUND: A soluble fragment of the epidermal growth factor receptor (EGFR) extracellular domain (sEGFR) can be detected in the serum of cancer patients, but the role of sEGFR is still unclear. MATERIALS AND METHODS: Blood samples from patients receiving chemotherapy for metastatic breast cancer were collected before (n = 101) and after 3 courses of therapy (n=39). Levels of sEGFR and serum HER-2/neu extracellular domain (ECD) were determined by standardized ELISA. RESULTS: A higher percentage of cancer patients (15%) showed sEGFR values below 45ng/mL compared with control subjects (3%, p15 ng/mL) also showed a shorter overall survival than those with normal values for both parameters (7.1 versus 15.4 months, p=0.03). Again, this difference was higher in patients with estrogen receptor-positive tumors (4.6 versus 15.4 month, p
