HER-2 tissue expression correlated with serum levels in breast cancer patients

We explored the relationship between circulating HER-2 extracellular domain and tissue HER-2 status in a group of 42 postmenopausal breast cancer patients. All patients were examined before adjuvant chemotherapy or other adjuvant treatment. Serum levels were measured by BAYER Advia Centaur System, Golden, CO (the cut-off level was in our conditions considered at 12 ng/ml). Tissue expression was assayed with the DAKO HercepTest, North America, Inc, Carpinteria, CA. Our findings that serum levels are in consonance with tissue expression could be important in metastatic breast cancer, when it is impossible to get a new tumour sample and establish the actual HER-2 status, which may be different from the primary tumour. Although we know that serum HER-2 concentration cannot be substituted for IHC or FISH, we have observed a statistically significant correlation between serum level concentration and tissue HER-2 status.