This study is designed as Phase II/III. Phase II is aimed to evaluate safety and efficacy of IRIS, and feasibility of FOLFIRI. Phase III is aimed to verify inferiority of the progression free survival of IRIS in comparison with FOLFIRI.

Inclusion Criteria:

• Histologically confirmed colorectal cancer
• Locally advanced and/or metastatic colorectal cancer
• Have prior chemotherapy as first line treatment
• No prior irinotecan administration
• Able to take oral medication
• Age 20 to 75
• Performance status 0 or 1 (ECOG)
• WBC 3,000-12,000 / mm^3
• Platelet ≥100,000 / mm^3
• AST and ALT ≤ 100 IU/L
• Creatinine ≤ 1.2 mg/dL
• Bilirubin ≤ 1.5 mg/dL

Exclusion Criteria:

• Prior radio therapy for colorectal cancer
• Other malignancies in the past 5 years
• Serious illness or medical condition