This trial is phase 2, open-label, multi-center, single arm study The total sample size will be 38 patients. Patient will be administered chemotherapy until disease progression. Gemcitabine will be administered at a dose of 1000 mg/m2 every 3weeks (on day 1 of each cycle) TS-1 will be administered 80 mg/m2 orally twice daily for 14 days every 3 weeks.