Adjuvant Capecitabine vs Gemcitabine Plus Cisplatin in Resected Extrahepatic Cholangiocarcinoma

Inclusion Criteria: * Patients aged 19 years and older * Histologically documented extrahepatic cholangiocarcinoma (perihilar or distal bile duct tumor) * Microscopic or macroscopic surgical resection (ie., R0 or R1 resection) * Regional lymph node metastasis according to the American Joint Committee on Cancer (AJCC) 7th edition * No distant metastasis * Eastern Cooperative Oncology Group (ECOG) performance status 0 \~ 1 * No prior chemotherapy or radiotherapy * Serum CA 19-9 \< 100 U/mL at the time of enrollment * Adequate bone marrow function as defined by platelets ≥ 100 x 109/L and neutrophils ≥ 1.5 x 109/L * Adequate renal function, with serum creatinine \< 1.5 x upper limit of normal (ULN) * Adequate hepatic function with serum total bilirubin \< 2 mg/dL, alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \< 2.5 x ULN * No other malignant disease apart from non-melanotic skin cancer or carcinoma in situ of the uterine cervix or any other non life-threatening cancer (i.e., prostate or thyroid cancer) except where treated with curative intent \> 5 years previously without evidence of relapse Written informed consent to the study Exclusion Criteria: * Medical or psychiatric conditions that compromise the patient's ability to give informed consent or to complete the protocol or a history of non-compliance * Histologies other than adenocarcinoma such as mixed hepatocellular carcinoma/cholangiocarcinoma, adenosquamous carcinoma or mixed adenocarcinoma/neuroendocrine carcinoma * Intrahepatic cholangiocarcinoma or gallbladder cancer * Obstruction of gastrointestinal tract * Active gastrointestinal bleeding * Myocardial infarction within 6 months prior to the study medication, and other clinically significant heart disease (e.g., unstable angina, congestive heart failure or uncontrolled hypertension) * Evidence of severe or uncontrolled systemic disease or any concurrent condition which in the investigator's opinion makes it undesirable for the patient to participate in the study or which would jeopardise compliance with the protocol * Female subjects who are pregnant or lactating, or males and females of reproductive potential not willing or not able to employ a highly effective method of birth control/contraception to prevent pregnancy from 2 weeks before receiving study drug until 3 months after receiving the last dose of study drug. A highly effective method of contraception is defined as having a low failure rate (\< 1% per year) when used consistently and correctly.