In this open-label, single-center, small sample size, randomised, parallel-group, controlled study, the investigators aim to assess efficacy and safety of addition of nimotuzumab to CS chemotherapy in patients with previously untreated advanced gastric adenocarcinoma. Sixty-two patients are required and randomly assigned (1:1) to each group.

The control regimen (CS chemotherapy) is recommended as the standard first-line regimen for advanced adenocarcinoma of the stomach or gastroesophageal junction in japan.

Inclusion Criteria:

1. provision of written informed consent;
2. male or female; and aged ≥ 18 years;
3. Histologically verified, untreated, metastatic or locally advanced inoperable adenocarcinoma or signet ring cell carcinoma of the stomach or gastroesophageal junction;
4. At least one radiographically documented measurable lesion according to Response Evaluation Criteria In Solid Tumors Version 1.1(RECIST1.1) Criteria;
5. An Eastern Cooperative Oncology Group (ECOG) performance status of 0-2; and a life expectancy ≥ 3months;
6. No previous palliative chemotherapy;
7. Adequate function of vital organs: white blood cells (WBC) ≥ 4.0×109/L, neutrophils (ANA) ≥ 1.5 × 109/L, platelets ≥ 100 × 109/L, hemoglobin ≥ 90g/L (blood transfusion is permitted if necessary), serum bilirubin ≤ 1 times the upper normal limit (UNL), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) < 2.5 times the UNL, alkaline phosphatase (AKP) ≤ 5 times the UNL, creatinine (Cr) ≤ 1 times the UNL, normal electrocardiography (ECG).

Exclusion Criteria:

1. pregnant or lactating patients, or reproductive women without effective contraception;
2. Patients with only non-measurable disease: small lesions (longest diameter < 10mm or pathological lymph nodes with ≥ 10 to < 15mm short axis), Bone lesions, leptomeningeal disease, ascites, pleural or pericardial effusion, lymphangitic involvement of skin or lung; abdominal masses/abdominal organomegaly identified by physical exam that is not measurable by reproducible imaging techniques.
3. Symptomatic of brain metastasis;
4. Patients with clinically severe comorbidity including diabetes mellitus, hypertension, heart disease, or chronic active hepatitis (HBV carrier can be enrolled if circumstance permits );
5. No previous radiotherapy for measurable lesions.