POF Versus FOLFOX Versus FOLFOX Plus ip Paclitaxel in AGC

Inclusion criteria: 1. Age 18-75 years; 2. Patients must have histologically or cytologically confirmed metastatic or unresectable gastric or gastroesophageal junction (GEJ) adenocarcinoma. GEJ adenocarcinoma may be classified according to Siewert's classification type I, II, or III. Histological documentation of local recurrence or metastasis is strongly encouraged, unless the risk of such a procedure outweighs the potential benefit of confirming the metastatic disease; 3. Patients must have disease that can be measurable radiographically measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) guidelines (version 1.1); 4. Patients may have received no prior chemotherapy for metastatic or unresectable disease. Patients may have received prior adjuvant therapy (chemotherapy and/or chemoradiation) if more than 6 months have elapsed between the end of adjuvant therapy and registration. 5. Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0-1; 6. An expected survival of ≥3months; 7. Major organ function has to meet the following criteria: (1) For results of blood routine test: Hemoglobin (HB) ≥80 g/L, ANC (absolute neutrophil count) ≥1.5 × 109/L, PLT (blood platelet) ≥75 × 109/L; (2) For results of biochemical tests: BLT (total bilirubin) ≤1.25 × the upper limit of normal (ULN), ALT (Alanine aminotransferase) and AST (aspartate aminotransferase ) ≤2.5 × ULN, liver metastases, if any, the ALT and AST ≤5 × ULN, Serum Cr（creatinine）≤1 × ULN, Endogenous creatinine clearance rate \>50ml/min; 8. The patient has an INR (international normalized ratio) ≤1.5 and an PTT（Partial Thromboplastin Time）≤3 seconds above the ULN if the patient is not on anticoagulation. If a patient is on full-dose anticoagulants, the following criteria should be met for enrollment: (1) The patient must have an in-range INR (usually between 2 and 3) on a stable dose of warfarin or on stable dose of LMW (Low molecular weight) heparin; (2) The patient must not have active bleeding or pathological conditions that carry high risk of bleeding (e.g. tumor involving major vessels, known varices) 9. Pregnancy test (serum or urine) has to be performed for woman of childbearing age within 7 days before enrolment and the test result must be negative. Men and women of childbearing potential must be willing to consent to using effective contraception while on treatment and for at least 3 months thereafter. 10. Ability to understand informed consent and signing of written informed consent document prior to initiation of protocol therapy. Exclusion criteria: 1. Patients who have ascites requiring frequent drainage; 2. Patients who have received previous chemotherapy for the treatment of metastatic or unresectable gastric or GEJ adenocarcinoma are ineligible; 3. Patients who have received previous pre- or post-operative chemotherapy or chemoradiation are ineligible if therapy was completed less than 6 months prior to study registration; 4. Patients with a history of another neoplastic disease within the past three years, excluding basal cell carcinoma of the skin, cervical carcinoma in situ, or nonmetastatic prostate cancer; 5. Patients with brain or central nervous system metastases, including leptomeningeal disease; 6. Pregnant (positive pregnancy test) or breast feeding; 7. Serious, non-healing wound, ulcer, or bone fracture; 8. Significant cardiac disease as defined as: unstable angina, New York Heart Association (NYHA) grade II or greater, congestive heart failure, history of myocardial infarction within 6 months; 9. Evidence of bleeding diathesis or coagulopathy; 10. History of a stroke or CVA within 6 months; 11. Clinically significant peripheral vascular disease; 12. Peripheral neuropathy grade ≥2 according to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 4.03; 13. Inability to comply with study and/or follow-up procedures; 14. Patients with any other medical condition or reason, in that investigator's opinion, makes the patient unstable to participate in a clinical trial.