“…Even though this was a tremendous success, the overall survival remained poor with a median of 13.8 months [3,4]. However, several case reports and few smaller studies have reported that a subgroup of HER2-positive mGC/mGEJC patients showed prolonged survival for several years under maintenance therapy with trastuzumab alone [5][6][7][8]. To date, a biomarker that reliably identifies this long-term responder to trastuzumab treatment remains elusive.…”