The invention provides a method for treatment of gastric cancer, which method is a postoperative adjuvant chemotherapy for gastric cancer, comprising orally administering, to a patient with gastric cancer in stage II, IIIA, or IIIB in a classification of the stage of gastric cancer, a pharmaceutical composition containing Tegafur, Gimeracil, and Oteracil potassium at a molar ratio of 1:0.4:1, at a dose of 50 to 150 mg/day as Tegafur dose and according to an administration schedule including, from within 45 days after a surgical operation of gastric cancer, drug administration for 28 consecutive days, followed by a rest period of 7 to 14 consecutive days.
The chemotherapy reduces the relapse rate after a surgical operation, thereby improving the survival rate.