Serum Her2 Level During Chemotherapy As A Biomarker For Advanced Gastric Cancer.

29Background: Recent studies showed that serum HER2 levels correlated with tissue HER2 status in gastric cancer. The aim of this prospective study (UMIN000006442, 000006445) was to investigate changes in serum HER2 levels and tissue HER2 status during chemotherapy for advanced gastric cancer (AGC). Methods: Chemotherapy (Capecitabine and cisplatin) with and without trastuzumab was administered to patients with HER2-positive and HER2-negative AGC, respectively. Serum HER2 level was measured using chemiluminescense immunoassay (CLIA) at 4 points: at the initial diagnosis, after two cycles of chemotherapy, at the initial evaluation of tumor response, and at the time of progression. If possible, second biopsy was performed at progression to compare tissue HER2 status before and after chemotherapy. Results: Thirty-three patients (14 HER2-positive and 19 HER2-negative) with a median age of 67 years (range 51-80) were recruited. The median baseline serum HER2 level of the HER2-positive group was significantly hi...