RT Journal Article SR Electronic T1 Changes in HER2 Expression and Amplification Status Following Preoperative Chemotherapy for Gastric Cancer JF In Vivo JO In Vivo FD International Institute of Anticancer Research SP 1491 OP 1498 DO 10.21873/invivo.11405 VO 32 IS 6 A1 SEI SHU A1 MAKOTO IIMORI A1 RYOTA NAKANISHI A1 TOMOKO JOGO A1 HIROSHI SAEKI A1 EIJI OKI A1 YOSHIHIKO MAEHARA YR 2018 UL http://iv.iiarjournals.org/content/32/6/1491.abstract AB Background: It is essential to establish a strategy for second-line treatment for human epidermal growth factor receptor 2 (HER2)-positive gastric cancer; however, HER2 expression status after chemotherapy treatment is not routinely determined. Materials and Methods: We analyzed 25 cases of gastric cancer that received preoperative chemotherapy and selected the six pre-treatment samples that were HER2-positive. Pre- and post-treatment tumor samples were examined for HER2 expression, and for HER2, epidermal growth factor receptor (EGFR), and hepatocyte growth factor receptor (MET) gene amplification. Results: Three patients had been treated with trastuzumab plus chemotherapy, and three patients with cytotoxic chemotherapy alone. Only one case that had an initial HER2 score of 3+ and had received trastuzumab plus chemotherapy remained HER2-positive after treatment. Decrease or loss of HER2 expression and amplification was observed in the other five patients. Amplification of EGFR or MET was not observed in any pre- or post-treatment specimens. Conclusion: Our data suggest that trastuzumab plus chemotherapy or chemotherapy alone may induce loss of HER2 positivity.