Comparison of Her2/Neu Oncoprotein in Serum and Tissue Samples in Women with Breast Cancer

BACKGROUND AND OBJECTIVES: Human Epidermal Growth Factor Receptor 2 (HER2/neu) is one of the most extensively studied proto-oncogens in breast cancer patients. Accurate and timely assessment of the HER2/neu over expression is pivotal for the identification of breast cancer patients that could benefit from HER2-targeted therapy. The present study was undertaken to investigate the diagnostic utility of serum HER2/neu testing by chemiluminescent immunoassay (CLIA) in breast cancer patients and compare it with the immunohistochemistry (IHC) method of HER2/neu expression. METHODS: Serum sample and tissue/paraffin block was collected from 52 patients with breast cancer before start of any anticancer regimen or hormonal therapy. The tissue specimens were processed in Histopathology lab. Sections were immunostained with anti –estrogen receptor (ER) , anti –progesteron receptor (PR) and anti HER2/neu receptor mouse monoclonal antibodies.) Serum HER2/neu was estimated using the chemiluminiscent immunoassay using 15ng/ml as the cut off. RESULTS: Out of 52 patients with breast cancer, serum HER2/neu was found elevated in 25(48.1%) patients and remaining 27(51.9%) showed normal serum HER2/neu concentrations. On IHC HER2/neu score was 3+ in 9(17.3%), 2+ in 10(19.2%), 1+ in 1(1.9%); while 32(61.5%) showed no HER2/neu expression. 31(59.6%) patients were ER positive and 28(53.8%) were PR positive. There was a significant correlation (P<0.001) of serum HER2 concentration with tissue expression of HER2/neu and Histological tumor grade. Serum HER2/neu levels showed a negative correlation with ER status (P=0.047) but no correlation with PR status. CONCLUSION: The result showed that the elevated serum HER2/neu was correlated with the IHC expression of HER2/neu in tissue and the histological grade of the tumor. Findings suggest that post initial tissue diagnosis (IHC HER2/neu), serum HER2 assay may supplement subsequent tissue tests to monitor disease status and response to therapy.