Efficacy and Safety of Trastuzumab, Capecitabine y Oxaliplatine as Treatment Gastric Cancer Metastatic (HER2)Positive

Inclusion Criteria: * Patients be able to grant a written informed consent or oral consent * Age ≥18 years old * Patients diagnosed with metastatic gastric or gastro-esophageal junction adenocarcinoma (HER2-positive), unresectable and histologically confirmed Measurable disease, following the new RECIST criteria, * HER2 positive tumors (primary or metastatic) with overexpression HER2 determinated by IHQ +++ (IHQ3+) o IHQ ++ confirmed by FISH/SISH positive (IHQ2+/FISH+) * ECOG ≤ 2 * Patients of childbearing potential (\< 12 months from last menstruation), they have to use effective means of contraception * Life expectancy more than 3 months * Adequate renal function: calculated creatinine clearance \> 50 mL/min * Adequate liver function: AST and ALT ≤2.5 x LSN (5 x LSN with liver metastasis), bilirubin 1,5 x LSN. alkaline phosphatase \< 2,5 x LSN (≤ 5 x LSN with liver metastasis o \< 10 x LSN with bone metastases Adequate haematological function: Hb ≥9 g/dl, neutrophils ≥ 1,5 x 109 /l and platelets 100 x 109 /l. * Normal Left Ventricle Fraction Ejection , LVEF\> 50% * Every patient should be treated and followed in his / her study site Exclusion Criteria: * Prior chemotherapy treatment for advanced/metastatic disease * Lack of physical integrity of the upper gastrointestinal tract or malabsorption * Patients with active gastrointestinal bleeding * Prior chemotherapeutic treatment for advanced / metastatic disease * Toxicity as a result of prior therapy (except alopecia)., for example. * Neurology toxicity grade ≥2NCI-CTCAE * Patients who received radiotherapy within 4 weeks prior to study treatment. * Major surgical procedures within 4 weeks prior to treatment without a total surgical recovery. * Past or current history of other malignancies (within the last 5-2 years prior to treatment start), patients with curatively treated basal cell carcinoma of the skin or in situ carcinoma of the cervix are eligible * Active and clinically significant cardiovascular disease, * History or current clinical evidence of brain metastasis * Patients undergoing transplantation allogenic requiring immunosuppressive treatment * Moderate or severe renal failure, creatinine clearance \< 50 mL/min, calculated by Cockcroft-Gault * Adequate liver function: bilirubin ≤1.5 x UL, GOT ( ASAT )/ GPT ( ALAT ) ≤2,5 LSN. Liver metastasis ≤ 5 x LSN, FA ≤ de 2,5 feces el LSN. * Adequate haematology function: neutrophils ≥ 1,5 x 109 /l and platelets 100 x 109 /l * Treatment with sorivudine and the analogous as brivudine. * Dihydropyrimidine proven dehydrogenase deficiency (DPD). * Patients who had received any drug, agent or investigational procedure, or who have participated in another research study within 30 days prior to initiation of treatment with study medication. * Hypersensitivity to any of the study drugs * Evidence of any other disease, metabolic dysfunction, physical examination finding or laboratory finding giving reasonable suspicion of a disease or condition that contraindicates the use of an investigational drug or puts the patient at high risk for treatment-related complications * Patients receiving chronic corticosteroid therapy or high dose (is allowed to use inhaled steroids and cycle short treatment with oral steroids for prevention of emesis or to stimulate appetite) * Pregnancy and lactation * Patients of childbearing potential not willing to use effective means of contraception. * History of psychiatric disorders that the investigator considered clinically significant, causing the patient give informed consent or interfere with compliance with study procedures.