Gemcitabine+ Capecitabine Vs Capecitabine in Curatively Resected Biliary Tract Cancer

This clinical trial is an open-label, multicenter, phase 3 clinical trial to study the efficacy and safety of adjuvant gemcitabine + capecitabine combination treatment in patients with resectable biliary tract cancer according to imaging studies after surgery. All the patients must complete a consent forms before participating in the clinical trial, and the estimated enrollment period is 36 months after IRB approval. Drug Dose and Schedule: * Cohort 1: Gemcitabine/Capecitabine, every 4 weeks, total 6 cycles gemcitabine1,000 mg/m2 over 30 min D1, D8, D15 capecitabine 1660 mg/m2, D1-21 * Cohort 2: Capecitabine, everu 3 weeks, total 8 cycles capecitabine 2,500 mg/m2 D1-14