JCOG1507: a phase III trial to confirm S-1 adjuvant chemotherapy for pathological stage II/III vulnerable elderly gastric cancer patients

INTERVENTION: Arm A: treatment free Arm B: Patients receive S‐1 orally twice a day for 4 weeks administration/2‐week discontinuation. The initial dose of S‐1 is reduced by >1 level versus the standard dose according to Ccr and type of surgery and is administered for 1 year after surgery. CONDITION: Gastric neoplasm PRIMARY OUTCOME: Overall survival SECONDARY OUTCOME: Relapse‐free survival, time‐to‐treatment‐failure, proportion of treatment continuation, relative dose intensity, adverse events, severe adverse events INCLUSION CRITERIA: 1) Histologically proven gastric adenocarcinoma 2) Pathological stage II/III defined by 14th edition of Japanese Classification of Gastric Carcinoma 3) Received R0 gastrectomy with D1+ or D2 lymphadenectomy 4) Either of the following surgery performed; i) Open laparotomy regardless of clinical stage and type of gastrectomy ii) Laparoscopic or laparoscope‐assisted distal, pylorus preserving, total or proximal gastrectomy for clinical stage I 5) Either of the followings: i) Weight loss < 15% and 30 mL/min <= Ccr for the patients received total gastrectomy ii) Weight loss < 15% and 30 mL/min <= Ccr < 80 mL/min for the patients not received total gastrectomy 6) Within 5 to 7 weeks after surgery 7) Aged 80 years old or older 8) Performance status of 0 or 1 9) No gastric stump cancer 10) No previous treatment of chemotherapy, radiation therapy, or molecular‐target therapy for any neoplasms. (History of hormone therapy mo