Randomized phase II/III study of 5-fluorouracil /l-leucovorin vs. 5-fluorouracil /l-leucovorin plus paclitaxel in gastric cancer with severe peritoneal metastasis (JCOG1108/WJOG7312G, abbreviation: GC_FL/FLTAX_P2/3)

INTERVENTION: A: 5‐FU/ l‐LV 5‐FU : 600 mg/m2/day, bolus (1 hour after start of l‐LV) : day 1, 8, 15, 22, 29, 36 l‐LV : 250 mg/m2/day, div (2 hours) : day 1, 8, 15, 22, 29, 36 q8w B: FLTAX 5‐FU : 500 mg/m2/day, bolus (1 hour after start of l‐LV) : day 1, 8, 15 l‐LV : 250 mg/m2/day, div (2 hours) : day 1, 8, 15 PTX : 60 mg/m2/day, div (1 hours) : day 1, 8, 15 q4w CONDITION: Gastric cancer PRIMARY OUTCOME: Phase II: Median survival time in both arms and proportion of treatment continuation at 8th week in FLTAX arm; ; Phase III: Overall survival SECONDARY OUTCOME: Phase II: Proportion of treatment continuation at 8th week in 5‐FU/l‐LV arm and adverse events in both arms ; ; Phase III: Adverse events, Proportion of oral intake improvement, Ascites drainage‐free survival, Proportion of ascites response, Proportion of ascites control, QOL, Time‐to‐treatment failure, Dose intensity INCLUSION CRITERIA: 1) Unresectable or recurrent gastric cancer with peritoneal metastasis 2) histologically confirmed adenocarcinoma 3) Massive ascites and/or inadequate oral intake. In case of massive ascites and inadequate oral intake, patients with PS0 or PS1 are eligible. 4) No metastasis to central nervous system 5) No fistula between tumor and other organ 6) No pleural effusion needed to be removed 7) Measurable or non‐measurable disease 8) Between the ages of 25 and 75 9) ECOG Performance status(PS): 0, 1, 2. In case of patients with PS2, massive ascites, and inadequate oral intake, they are ineligible. 10) HER2 untested or negative in case of tested 11) No previous chemotherapy or radiotherapy or chemoradiotherapy or hormone therapy for other malignancies (neoadjuvant or adjuvant chemotherapy for gastric cancer is allowed as long as it was completed at least 24 weeks prior to randomization) 12) Adequate organ function as evidenced by the follo