The clinical hypothesis of this study is that the addition of Panitumumab to the first line treatment combination of docetaxel plus cisplatin will provide benefit to patients with advanced gastric or gastroesophageal junction adenocarcinoma.

Inclusion Criteria:

• Written informed consent Inclusion:
• Age ≥ 18 years
• Histologically or cytologically confirmed adenocarcinoma of the stomach or gastroesophageal junction with advanced unresectable or metastatic disease.
• Measurable disease per the revised RECIST (Response Evaluation Criteria in Solid Tumor) Guidelines
• ECOG performance score of 0 - 2
• Within seven days prior to initiating study treatment:Haematology:Neutrophils ≥ 1.5x109, Platelets ≥ 100x10/ L, Hemoglobin ≥ 9g/dL. Hepatic functions: Total bilirubin ≤ 1.5 time the upper normal limit (UNL),ASAT ≤ 2.5xUNL in absence of liver metastases, or ≤5xUNL in presence of liver metastases,ALAT ≤ 2.5xUNL in absence of liver metastases, or ≤5xUNL in presence of liver metastases. Renal function: creatinine clearance ≥50 mL/min. Metabolic Function: Magnesium ≥ lower limit of normal, Calcium ≥ lower limit of normal.

Exclusion Criteria:

• Prior chemotherapy or other anticancer therapy for advanced unresectable or metastatic disease (1st line)
• Prior anti-EGFR antibody therapy (e.g. cetuximab) or treatment with small molecule EGFR inhibitors (e.g. erlotinib).
• HER2-positive tumor (centrally assessed)
• Past or current history (within the last 5 years prior to treatment start) of other malignancies except gastric cancer (Patients with curatively treated basal and squamous cell carcinoma of the skin or in situ carcinoma of the cervix are eligible)
• Current or prior history of central nervous system metastases
• 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 Treatment with any other investigational agent, or participation in another clinical trial within 30 days prior to entering this study
• Known hypersensitivity to any of the study drugs
• Clinically significant cardiovascular disease (including myocardial infarction, unstable angina, symptomatic congestive heart failure, serious uncontrolled cardiac arrhythmia) ≤ 1 year before enrollment
• History of interstitial lung disease e.g. pneumonitis or pulmonary fibrosis or evidence of interstitial lung disease on baseline chest CT scan.
• Subject pregnant or breast feeding, or planning to become pregnant within 6 months after the end of treatment.
• Subject (male or female) is not willing to use highly effective methods of contraception (per institutional standard) during treatment and for 6 months (male or female) after the end of treatment.