Tegafur-Uracil and Leucovorin or S-1 in Treating Patients With Stage III Colon Cancer That Has Been Completely Removed by Surgery

RATIONALE: Drugs used in chemotherapy, such as tegafur-uracil, leucovorin, and S-1, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. It is not yet known whether giving tegafur-uracil together with leucovorin is more effective than giving S-1 in treating patients with stage III colon cancer.
PURPOSE: This randomized phase III trial is studying giving tegafur-uracil together with leucovorin to see how well it works compared with giving S-1 in treating patients with stage III colon cancer that has been completely removed by surgery.