DISEASE CHARACTERISTICS:

• Histologically confirmed adenocarcinoma of the colon or rectum

  • No other histological types

• Metastatic, unresectable disease

  • No bone metastases only
• Unidimensionally measurable metastatic disease
• No CNS metastases

PATIENT CHARACTERISTICS:

• WHO performance status (PS) 0-2 OR Karnofsky PS 70-100%
• Life expectancy ≥ 12 weeks
• ANC > 1,500/mm³
• Platelet count ≥ 100,000/mm³
• Hemoglobin ≥ 10 g/dL
• Bilirubin ≤ 1.25 times normal (1.5 times normal in presence of hepatic metastases)
• AST and ALT < 3 times normal (5 times normal in presence of hepatic metastases)
• Creatinine < 1.25 times normal
• No proteinuria
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No other cancer in the past 5 years except for carcinoma in situ of the uterine cervix or basal cell skin cancer
• No hypersensitivity to fluorouracil
• No hypersensitivity to leucovorin calcium, bevacizumab, or their excipients
• No hypersensitivity to Chinese hamster ovarian cell products or other recombinant humanized or nonhumanized monoclonal antibodies
• No allergy to irinotecan hydrochloride
• No prior reaction to attenuated vaccines (fever, jaundice)
• No poor nutritional status
• No Biermer anemia or other anemia due to vitamin B12 deficiency
• No uncontrolled symptomatic occlusion or subocclusion
• No medullary hypoplasia or severe insufficiency
• No prior chronic intestinal disease
• No Gilbert's syndrome
• No intra-abdominal inflammatory reaction (e.g., gastroduodenal ulcer, diverticulitis, or colitis)
• No chronic intestinal inflammatory disease

• No thromboembolic arterial condition in the past 6 months, including any of the following:

  • Cardiovascular accident
  • Transient ischemic attack
  • Myocardial infarction
• No infection or serious noncancerous disease

• No condition that is unstable or would increase risk to the patient, including any of the following:

  • Unstable angina
  • Poorly controlled hypertension
  • Severe cardiac insufficiency
  • Serious arrhythmia
  • Bleeding diathesis
  • Pulmonary disease at risk of decompensation
• No familial, geographical, social, or psychological condition that would preclude study participation
• No prisoners or patients without guardians

PRIOR CONCURRENT THERAPY:

• At least 8 weeks since prior surgery
• At least 6 months since prior adjuvant chemotherapy
• At least 1 month since prior palliative chemotherapy
• No prior abdominal or pelvic radiotherapy
• At least 30 days since prior participation in another investigational study
• No prior bevacizumab
• No extensive intestinal resection (e.g., partial colectomy or extensive thin resection)
• No concurrent warfarin, Hypericum perforatum (St. John's wort), or prophylactic phenytoin