Inclusion Criteria:

1. Histological diagnosis of colorectral adenocarcinoma.
2. Measurable or assessable lesions.
3. Age: 18 ~ 75 years.
4. Performance Status (ECOG): 0 ~ 2.
5. No prior chemotherapy. Adjuvant chemotherapy is not defined as previous therapy.
6. No history of radiotherapy to the abdomen.
7. Adequate function of major organs (bone marrow, heart, lungs, liver etc.). WBC 3,500/mm3 and 12,000/mm3. Hb 10.0 g/dl. Platelet count 100,000/mm3. GOT and GPT 2.5times the upper limit of normal (excluding liver metastasis). T-Bil 2.0mg/dl. Creatinine <1.5 mg/dl Normal ECG (not considering clinically unimportant arrhythmias and ischemic changes).
8. Predicted survival for >3 months.
9. Able to give written informed consent.

Exclusion Criteria:

1. Severe pleural effusion or ascites.
2. Metastasis to the central nervous system (CNS).
3. Active gastrointestinal bleeding.
4. Active infection.
5. Diarrhea (watery stools).
6. Uncontrolled ischemic heart disease.
7. Serious complications (such as intestinal paralysis, intestinal obstruction, interstitial pneumonia or pulmonary fibrosis, uncontrolled diabetes mellitus, heart failure, renal failure, or hepatic failure).
8. Active multiple cancer.
9. Severe mental disorder.
10. Pregnancy, possible pregnancy, or breast-feeding.
11. Flucytosine treatment
12. Gilbert’s syndrome.
13. Judged to be ineligible for this protocol by the attending physician.