To compare efficacy and safety of Gemcitabine versus S-1 adjuvant therapy after hemihepatectomy.

There is no standard adjuvant therapy after liver hemi-hepatectomy due to bile duct cancer, because of high surgical morbidity ratio and high adverse event ratio of adjuvant therapy. For example, our preliminary results showed that regular gemcitabine administration (1000mg/m2, day 1, 8, 15 every 4 weeks) after hemihepatectomy was too toxic and induced severe leukocytopenia and/or thrombocytopenia. Formerly, the investigators planned the study to decide more safety adjuvant protocol (recommend dose: RD) for Gemcitabine or S-1 after hemihepatectomy using Continuous Reassessment Method (CRM) analysis and decided the recommend doses. Note: In the former study, the investigators decided that tolerable ratio of Dose Limiting Toxicity (DLT) would be less than 10%.

Herein, the investigators planned the study to evaluate efficacy (recurrent free survival as primary outcome, and overall-survival as secondary outcome) and safety (as secondary outcome) in our recommended protocols, and to compare the efficacy as randomized control trial.

Inclusion Criteria:

1. Biliary tract cancer (BTC) (>= Unio Internationalis Contra Cancrum (UICC) Stage IB), adenocarcinoma
2. R0 or R1 resection
3. no obvious recurrent lesion
4. 20 years old or more
5. Eastern Cooperative Oncology Group (ECOG) performance status must be 0 or 1
6. The patient underwent no other treatment than surgery for BTC
7. Neutrophil must be over 1500/μl, Hemoglobin must be over 9.0g/dL, platelet must be over 100,000/μl, Aspartate transaminase (AST) and Alanine aminotransferase (ALT) must be less than 150 IU/L, total bilirubin must be less than 1.5 mg/dL, Creatinine must be less than 1.2 mg/dl, and Creatinine clearance must be over 60 mL/min
8. The patient can intake drugs per os.
9. From 4 to 12 weeks after the surgery
10. Written informed consent

Exclusion Criteria:

1. Existence of active double cancer
2. The patient suffered from severe drug allergy
3. Sever complications (interstitial pneumonia, heart failure, renal failure, liver failure, ileus, incontrollable diabetes mellitus, and so on)
4. Any active infections exist.
5. Pregnancy
6. Severe mental disorder
7. Others