Combination Chemotherapy and Bevacizumab in Treating Patients With Metastatic Colorectal Cancer

DISEASE CHARACTERISTICS: * Diagnosis of metastatic adenocarcinoma of the colon or rectum * Not curable by surgery * Genotype UGT1A1\*1/UGT1A1\*1 or UGT1A1\*1/ UGT1A1\*28 * Measurable disease * No original tumor in place * No secondary cerebral metastases PATIENT CHARACTERISTICS: Inclusion criteria: * WHO performance status 0-2 * Life expectancy ≥ 3 months * Absolute neutrophil count ≥ 1,500/mm3 * Platelet count ≥ 100,000/mm3 * Hemoglobin ≥ 9.0 g/dL * Total bilirubin ≤ 1.5 times normal * Alkaline phosphatase ≤ 2.5 times normal (5 times normal if liver involvement) * Not pregnant or nursing * Negative pregnancy test * Fertile patients of must use effective contraception Exclusion criteria: * Progressive gastrointestinal ulcer, hemorrhagic ulcer, or perforation in the past 6 months * Enteropathy or chronic diarrhea * Proteinuria \> 500 mg/24 hours * Active cardiac disease * Uncontrolled hypertension * Myocardial infarction in the past 12 months * Angina * NYHA grade II-IV congestive heart disease * Severe arrhythmia even with treatment * Peripheral vascular disease ≥ grade II * Nonhealing wound, ulcer, or severe bone fracture * Hemorrhagic diatheses or coagulopathy * Severe or uncontrolled infection * Severe or uncontrolled medical condition * Other malignant disease in the past 5 years except curatively treated basal cell skin cancer or carcinoma in situ of the uterine cervix * Severe traumatic injury within the past 4 weeks PRIOR CONCURRENT THERAPY: * No prior chemotherapy for metastatic disease * One prior regimen of chemotherapy in the neoadjuvant or adjuvant setting for the original tumor allowed * At least 6 months since prior chemotherapy * No prior irinotecan hydrochloride or bevacizumab * No oral or parenteral anticoagulant therapy within the past 10 days * Warfarin allowed provided INR \< 1.5 * No major surgery or biopsy within the past 4 weeks * No puncture in the past 7 days * No planned major surgery * No concurrent daily or chronic aspirin (\> 325 mg/day), anti-inflammatories, or steroids * No other concurrent anticancer therapy