Background: The purpose of this study was to determine the positive predictive value (PPV) of positive serum human epidermal growth factor receptor-2 (HER-2) for monitoring women with breast cancer following diagnosis and treatment in a routine clinical setting. Methods: Serum HER-2 was measured in 1348 patients with breast cancer: 837 during routine oncology clinic visits and 511 following new diagnosis. All patients with positive serum HER-2, 1/5 of negative patients from the oncology clinic, and all the newly diagnosed were followed; a total of 862 patients. Serum HER-2 was measured using the Bayer ADVIA Centaur assay. Tissue HER-2 was determined using immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). IHC q3 or IHC q2 and FISH)2.0 were positive. Patients were considered to have positive serum HER-2 when at least two values were

Our study demonstrated a profound activation of the EGFR system. HB-EGF was increased by factor 10 in cancer tissue and related to the biological aggressiveness of the tumors, and pHER2, HB-EGF and BTC were associated with poor clinical outcome.

Monitoring tissue HER-2-positive breast cancer patients with serum HER-2 has a sufficient sensitivity to detect metastatic recurrence, while its use in monitoring of tissue HER-2-negative patients is unsatisfactory.

Detection of HER-2 overexpression by measuring HER-2 in tissue extracts by ELISA seems to be more sensitive than IHC and FISH. This suggests that some patients deprived of Herceptin treatment may benefit from this treatment and may also explain the conversion phenomenon from HER-2-negative to HER-2-positive observed in relapse and metastatic disease.

S-HER2Ab can be measured accurately with the ImmunoCAP 100. There is an increased prevalence and concentration of S-HER2Ab in breast cancer patients but no correlation with HER2 gene amplification. We conclude that autoantibodies against HER2 do not seem to be the cause of HER2 gene amplification.