A Phase II Study of Conversion Surgery After IP Paclitaxel With XELOX Chemotherapy in AGC With Peritoneal Dissemination

Inclusion Criteria: 1. Histologically or cytologically confirmed advanced gastric cancer adenocarcinoma 2. Peritoneal metastasis histopathologically confirmed by laparoscopy or laparotomy and PCI \<12 (including patients with no gross peritoneal lesion and cytology positive) 3. No prior surgery for curative aim and previous chemotherapy for recurrent/metastatic gastric cancer 4. Patient who is willing and able to provide written informed consent/assent for the trial 5. Age between 19 and 75 years 6. Measurable lesion according to RECIST 1.1 criteria 7. ECOG performance status 0-1 8. Have adequate organ function * ANC ≥ 2,000/uL, * hemoglobin ≥ 9.0g/dL * platelet ≥ 100,000/uL * total Bilirubin: ≤ 1.5 × upper normal limit * Creatinine ≤ 1.5 × upper normal limit or Creatinine clearance ≥ 60ml/min * AST/ALT ≤ 3.0 x upper normal limit * Albumin ≥ 2.5 g/dL * PT or INR, aPTT ≤ 1.5 × upper normal limit 9. Should agree to use an adequate method of contraception Exclusion Criteria: 1. Previous systemic chemotherapy for metastatic/recurrent advanced gastric cancer 2. Patient who has distant metastasis or para-aortic lymph node metastasis or retroperitoneal metastasis except peritoneal metastasis. (But the patient who has ovarian metastasis with resectable status can be enrolled.) 3. Primary tumor cannot be resected because of direct invasion to other important organ. (But, if the invaded organ can be resected together, such as spleen, gallbladder, distal pancreas, and liver, the patient can be enrolled) 4. BMI ≤ 18.5 kg/m2 5. HER2 positive patient (IHC 3+, 2+ with in situ hybridization +) 6. Remnant gastric cancer 7. Intolerable to oral intake of chemotherapeutic agent or have malabsorption syndrome 8. Known additional malignancy that is progressing or requires active treatment in recent 3 years (excluding skin basal cell carcinoma, skin squamous cell carcinoma, thyroid cancer, or in situ cervix cancer that has undergone potentially curative therapy) 9. Symtomatic CNS metastasis and/or leptomeningeal seeding 10. Autoimmune disease in recent 2 years requiring systemic therapy 11. Clinically significant heart disease 12. Peripheral neuropathy ≥ Grade 2 13. Pregnant or breastfeeding, or expecting to conceive or father children within the projected duration of the trial, starting with the pre-screening or screening visit through 120 days after the last dose of trial treatment 14. History of HIV, HBV, or HCV