Evaluation of serum HER2-ECD levels in patients with gastric cancer.

Background: Determination of the human epidermal growth factor receptor 2 (HER2) status of gastric cancer patients is indispensable in clinical practice. However, the clinical value of serum HER2-extracellular domain (ECD) in gastric cancer has not yet been defined.

Methods: The serum level of HER2-ECD was measured using the chemiluminescence immunoassay method, and its relationship with tissue HER2 status and clinicopathologic features was examined. Transition of serum HER2-ECD level was examined in patients during chemotherapy to clarify the correlation between changes in the level of HER2-ECD in serum and response to chemotherapy.

Results: A total of 150 gastric cancer patients were enrolled in this study; changes in HER2-ECD level were examined in 36 of these patients during chemotherapy. Serum levels of HER2-ECD ranged from 4.8 to 180.0 ng/ml (median 9.2 ng/ml) and were positive (cutoff value 15.2 ng/ml) in ten patients (6.7 %). There was a significant correlation between serum HER2-ECD level and tissue HER2 status (P < 0.001); however, no correlation with TNM stage was found. Change in serum HER2-ECD level during chemotherapy was significantly correlated with response to chemotherapy in patients with HER2-positive tumor tissue.

Conclusions: Serum HER2-ECD is a potential biomarker of gastric cancer and could be used as a diagnostic marker with regard to tissue HER2 status, and also as a monitoring marker in relation to response to chemotherapy.