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