Phase II - Inoperable/unresectable locally advanced and/or metastatic, histologically (or cytologically) confirmed adenocarcinoma or undifferentiated carcinoma of the stomach or gastro-esophageal junction presenting for first line palliative systemic treatment. Prior adjuvant chemoradiotherapy for gastric or gastroesophageal junction adenocarcinoma is allowed as long as the patient has completed adjuvant therapy >= 6 months prior to study entry. Patients need to have at least one site of measurable disease as defined by RECIST criteria.