Bevacizumab Plus Fluorouracil and Leucovorin in Treating Patients With Locally Advanced or Metastatic Stage IV Colorectal Cancer That Has Progressed After Standard Chemotherapy

DISEASE CHARACTERISTICS: Histologically or cytologically confirmed colorectal adenocarcinoma Stage IV (metastatic) disease Not curable by surgery or radiotherapy Must have received prior standard chemotherapy regimens, including oxaliplatin and irinotecan, and meet both of the following criteria: Disease progression during or after irinotecan-based chemotherapy for metastatic disease OR relapsed disease within 6 months after adjuvant irinotecan-based therapy Disease progression during or after oxaliplatin-based chemotherapy for metastatic disease OR relapsed disease within 6 months after adjuvant oxaliplatin-based therapy No brain metastases PATIENT CHARACTERISTICS: Age 18 and over Performance status ECOG 0-2 OR Karnofsky 60-100% Life expectancy Not specified Hematopoietic Absolute granulocyte count at least 1,500/mm^3 Platelet count at least 100,000/mm^3 Hemoglobin at least 9 g/dL (transfusion allowed) No evidence of bleeding diathesis or coagulopathy Hepatic Bilirubin no greater than 1.5 mg/dL AST less than 5 times upper limit of normal (ULN) Alkaline phosphatase less than 5 times ULN PT and INR no greater than 1.5 times ULN PTT no greater than ULN Renal Creatinine no greater than 1.5 times ULN Proteinuria less than grade 1 OR Proteinuria less than 500 mg/24 hours Cardiovascular No prior stroke No uncontrolled high blood pressure No symptomatic congestive heart failure No unstable angina pectoris No cardiac arrhythmia No myocardial infarction within the past 6 months No New York Heart Association class III or IV heart disease No thromboembolism within the past 6 months Other Chemonaive Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception during and for at least 3 months after study participation No significant traumatic injury within the past 6 weeks No prior allergic reaction attributed to compounds of similar chemical or biological composition to bevacizumab or other study agents No active infection No psychiatric illness or social situation that would preclude study compliance No serious nonhealing wound (including wounds healing by secondary intention), ulcer, or bone fracture No CNS disease, including either of the following: Primary brain tumor Seizures not controlled with standard medical therapy PRIOR CONCURRENT THERAPY: Biologic therapy At least 8 weeks since prior monoclonal antibody therapy No prior bevacizumab Chemotherapy See Disease Characteristics Endocrine therapy Not specified Radiotherapy At least 4 weeks since prior major radiotherapy (e.g., chest or bone palliative radiotherapy) Surgery More than 6 weeks since prior major surgical procedure or open biopsy More than 7 days since prior fine needle aspiration or core biopsy No concurrent surgery Other Recovered from prior therapy At least 3 weeks since prior cytotoxic agents No concurrent therapeutic anticoagulation Prophylactic anticoagulation of venous access devices allowed provided PT/INR or PTT criteria are met No concurrent chronic aspirin (greater than 325 mg/day) or nonsteroidal anti-inflammatory drugs No concurrent combination antiretroviral therapy for HIV-positive patients No other concurrent investigational or commercial agents for the malignancy