Study of the measurement of serum extracellular domain of HER-2/neu protein with CLIA method.

OBJECTIVE

Immunohistochemistry (IHC) and Fluorescent In Situ Hybridization (FISH) are important technologies to examine the protein expression and gene amplification of human epidermal growth factor receptor type 2/neu (HER-2/neu), respectively, in breast cancer tumors; however, tumor samples are not always available for examination. Therefore, an easy and sensitive examination to detect HER2-overexpressed tumors should be developed. The extracellular domain of HER-2/neu protein (HER2ECD) has been reported to be observed in the serum of many patients with metastatic breast cancer. In this study we assessed the clinical usefulness of serum HER2ECD (sHER2ECD) as a biological marker in breast cancer.

METHOD

We measured sHER2ECD levels in 108 patients with breast cancer using the ADVIA Centaur assay system, and conventional tumor markers, i.e. CEA and CA15-3, using enzyme or chemiluminescent immunoassay. The sHER2ECD levels were compared with the levels of tumor markers and clinical characteristics.

RESULTS

Patients with primary breast cancer who had four or more lymph nodes involved (n=6) showed significantly higher sHER2ECD values than those with no nodes involved (n=57, p<0.05) and those with 1 to 3 nodes involved (n=15, p<0.01). In the IHC-positive group, the positive rate of sHER2ECD was higher than those of CA15-3 or CEA. In metastatic breast cancer, the combination of sHER2ECD and CA15-3 showed the highest positive rate (81.5%). In all 3 patients with HER2-overexpressed cancer showing a partial response (PR) or complete response (CR) to trastuzumab therapy, sHER2ECD levels declined after treatment (39.9 to 58.7%).

CONCLUSION

The sHER2ECD assay by the CLIA method may be useful for the diagnosis and monitoring of metastatic/recurrent breast cancer.