Inclusion Criteria:  histologically confirmed non-resectable locally advanced, recurrent, or metastatic adenocarcinoma of the stomach or gastro-esophageal junction; tumor samples scored as 3+ on immunohistochemistry or FISH (Fluorescence in situ Hybridization) positive (HER2:CEP17 ratio ≥2); measurable disease; treated by trastuzumab, platin (cisplatine or oxaliplatine), fluoropyrimidine (5-FU or capecitabine) +/- taxanes (docetaxel or paclitaxel), as first-line therapy for advanced gastric cancer.  Exclusion Criteria:  previous chemotherapy by taxane for metastatic disease, previous anti-HER2 therapy.