Individual Dosage Selection of Irinotecan (CPT-11) Based on UGT1A1 Genotype in Metastatic Colorectal Cancer Patients

Inclusion Criteria: 1. Histologically confirmed colorectal cancer patients who received no prior chemotherapy or failed to 1st line treatments 2. At least one measurable lesion by Response Evaluation Criteria in Solid Tumors (RECIST) criteria 3. Aged 18 years or older 4. ECOG performance status of ≤ 2. 5. Anticipated life expectancy of ≥ 3 months. 6. UGT1A1 genotype tested. Categorized into Wild (UGT1A1\*1/\*1), Hetero (UGT1A1\*1/ \*28, UGT1A1\*1/ \*6), and Homo (UGT1A1\*28/\*28, UGT1A1\*6/\*6, UGT1A1\*28/\*6). 7. Adequate organ function, including bone marrow, kidney and liver. * ANC ≥ 1.5×109/L and hemoglobin ≥ 9g/dL and platelet count ≥ 100×109/L * Serum total bilirubin ≤ 1.5 x ULN, alkaline phosphatase ≤ 2.5 x ULN, Serum ALT and AST ≤ 2.5 x ULN (Serum ALT and AST ≤ 5 x ULN, if liver metastases are present) * Serum creatinine ≤ 1.5 x ULN or CLcr \> 60 ml/min 8. Written informed consent can be obtained prior to their participation in the trial. Exclusion Criteria: 1. Pregnant or breast feeding women. 2. Subjects who have previously received CPT-11 treatment. 3. Serious concurrent complication, severe active infection. 4. Subjects with chronic diarrhea, acute or sub acute Intestinal obstruction. 5. Subjects with uncontrolled CNS metastasis or epilepsia or severe psychiatric disorders. 6. Subjects who are regarded to be unsuitable for this trial by the investigator. 7. Subjects who are participating in other clinical trials.