Inclusion Criteria: 1. Patients with histological or cytological diagnosis of biliary tract cancer who haven't received cisplatin previously 2. Patients who is planned to receive chemotherapy including gemcitabine and cisplatin for biliary cancer for more than 12 weeks 3. Older than 20 years old 4. Eastern Cooperative Oncology Group Performance status of 0 or 1 5. Adequate main organ function 6. Fully oral intake ability to drink 500ml of solution before chemotherapy 7. Estimated life expectancy no less than 3 months 8. Written informed consent