From the results of our previous phase III study (JCOG9205), continuous infusion of 5-fluorouracil has remained to be a control arm of this study. This study investigates the superiority of a combination of irinotecan plus cisplatin and non-inferiority of S-1, a oral fluoropyrimidine, compared to continuous infusion of 5-fluorouracil at the point of overall survival, and the planned number of enrolled patients is 690 (230/arm).