I. To evaluate the addition of AMG 337 to mFOLFOX6 chemotherapy and also to evaluate the placebo/mFOLFOX6 chemotherapy combination in the first line treatment of patients with Her2Neu negative and high c-MET expressing advanced esophagogastric and GEJ adenocarcinoma, with regards to overall survival (OS). (Phase II) II. To evaluate the addition of AMG 337 to mFOLFOX6 chemotherapy and also to evaluate the placebo/mFOLFOX6 chemotherapy combination in the first line treatment of patients with Her2Neu negative and high c-MET expressing advanced esophagogastric and GEJ adenocarcinoma, with regards to response rate and disease control rate. (Phase II) III. To evaluate the addition of AMG 337 to mFOLFOX6 chemotherapy and also to evaluate the placebo/mFOLFOX6 chemotherapy combination in the first line treatment of patients with Her2Neu negative and high c-MET expressing advanced esophagogastric and GEJ adenocarcinoma, with regards to toxicity rates. (Phase II) IV. To evaluate the addition of AMG 337 to mFOLFOX6 chemotherapy and also to evaluate the placebo/mFOLFOX6 chemotherapy combination in the first line treatment of patients with Her2Neu negative and high c-MET expressing advanced esophagogastric and GEJ adenocarcinoma, with regards to time to development of new metastasis. (Phase II) V. To evaluate the addition of AMG 337 to mFOLFOX6 chemotherapy and also to evaluate the placebo/mFOLFOX6 chemotherapy combination in the first line treatment of patients with Her2Neu negative and high c-MET expressing advanced esophagogastric and GEJ adenocarcinoma, with regards to evaluation of MET amplification. (Phase II) VI. To evaluate the addition of AMG 337 to mFOLFOX6 chemotherapy and also to evaluate the placebo/mFOLFOX6 chemotherapy combination in the first line treatment of patients with Her2Neu negative and high c-MET expressing advanced esophagogastric and GEJ adenocarcinoma, with regards to evaluation of MET amplification and MET expression as determined by DAKO immunohistochemistry (IHC) for comparison to Ventana IHC. (Phase II) VII. To evaluate the addition of AMG 337 to mFOLFOX6 chemotherapy and also to evaluate the placebo/mFOLFOX6 chemotherapy combination in the first line treatment of patients with Her2Neu negative and high c-MET expressing advanced esophagogastric and GEJ adenocarcinoma, with regards to a retrospective re-evaluation of the cutpoint used by the computer algorithm for c-MET IHC to assess its ability to distinguish responding versus non-responding patients will be undertaken in this population, so that a potentially more optimal cutpoint to define high c-MET tumors in patients can be identified. (Phase II)