S-1 and Cisplatin in Treating Patients Who Are Undergoing Surgery for Stage III Stomach Cancer

RATIONALE: Drugs used in chemotherapy, such as S-1 and cisplatin, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving more than one drug (combination chemotherapy) may kill more tumor cells. Giving chemotherapy before surgery may shrink the tumor so that it can be removed. It is not yet known whether giving S-1 together with cisplatin before surgery is more effective than surgery followed by S-1 in treating stomach cancer. PURPOSE: This randomized phase III trial is studying how well giving S-1 together with cisplatin before surgery works compared to surgery followed by S-1 in treating patients with stage III stomach cancer.