INTRODUCTION: The growth factor receptors EGFR and HER-2/neu are targets for new treatment strategies and are of potential use as prognostic and predictive factors. However, the optimal method of determination in order to obtain clinically relevant information remains a source of controversy. METHODS: HER-2/neu and EGFR expression was examined by immunohistochemistry in primary tumors of patients with breast cancer. In addition, serum was tested for the extracellular domains of HER-2/neu (HER-2/neu ECD) and EGFR (sEGFR) before initiation of therapy for metastatic disease (n=76). The course of disease from the time of metastasis with regard to these parameters was evaluated by univariate and multivariate analyses. RESULTS: HER-2/neu ECD levels at the time of metastatic disease were correlated with HER-2/neu expression determined by immunohistochemistry from primary tumors (p=0.001). No correlation was observed between expression of EGFR in primary tumors and sEGFR serum levels. HER-2/neu ECD and sEGFR levels at the onset of metastatic disease did not show a significant impact on overall survival. CONCLUSIONS: Determination of HER-2/neu ECD levels in the serum measured by ELISA at the onset of metastatic disease could offer an alternative to immunohistochemistry of the primary tumor since serum levels are correlated with protein expression in primary tumors. In contrast, no such correlation was observed for EGFR.
