Background: Survival of HER2+ metastatic GC is prolonged by trastuzumab when administered with CF/X (VanCutsem, ASCO 2009). Lapatinib inhibits both EGFR1 and HER2, is active in HER2+ GC lines, and has shown clinical activity in uncontrolled phase II GC trials. A phase III trial of lapatinib with X + oxaliplatin in HER2+ (FISH) GC is closed to recruitment. Additional unaddressed questions include the efficacy and safety of lapatinib with ECF/X (epirubicin + cisplatin + 5-FU or capecitabine (X), which is a preferred chemotherapy (CT) regimen in GC), and its activity in patients (pts) with discordant FISH or IHC HER2 status or EGFR1+. Methods: This is a phase II, randomized, double- blind, placebo controlled, multicenter trial sponsored by the EORTC. About 480 pts with adenocarcinoma of the stomach or esophagogastric junction not amenable to curative surgery and without prior palliative CT are screened centrally for HER2/EGFR1 by FISH and IHC. Patients are enrolled into one of two strata: 1) HER2 FISH- and IHC 2/3+, or 2) HER2 IHC 0/+ and EGFR1 FISH+ or IHC 2/3+. Pts HER2 FISH+/IHC 2/3+ and pts without HER2/EGFR1 by FISH/IHC will be excluded. 168 pts are anticipated to be randomized to lapatinib 1,250 mg cont. until progression or placebo, administered 6 cycles of ECF or ECX (72/96 in stratum 1/2, respectively).The primary endpoint is progression-free survival (PFS) in stratum 2 and 77 events are needed for 80% power to detect an increase in PFS from 4 to 6.5 months with lapatinib (HR=0.615, one-sided alpha 10%). Secondary endpoints include PFS, toxicity, response rate, overall survival, and correlation of HER2/EGFR1 status with response. Currently, half of all screened patients (19/38) have been randomized. So far, 8/38 (21%) pts were HER2+ according TOGA criteria. By FISH or IHC, 14/38 were EGFR1+, with 4/14 pts double HER2/EGFR+. Enrolment continues in 5 centers with about 4-10 patients per month. A safety cohort analysis will be performed in the first 15 pts receiving lapatinib. Conclusions: This is the first trial to analyze prospectively and separately the role of lapatinib combined with chemotherapy in EGFR1+ GC pts stratified by FISH/ IHC.