Patients will be treated with irinotecan (150 mg/m2) followed by oxaliplatin (85 mg/m2) on day 1 and S-1 (80 mg/m2/day) from day 1 to 14 every 3 weeks. Patients will receive up to a planned treatment of maximum 12 cycles of chemotherapy. Response assessment will be performed every 2 cycles of chemotherapy.