Gemcitabine and Bevacizumab in Treating Patients With Pancreatic Cancer That Has Been Completely Removed By Surgery

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed adenocarcinoma of the pancreas * Completely resected disease * Underwent 1 of the following procedures 3-8 weeks ago: * Standard pancreaticoduodenectomy (for tumors of the pancreatic head) * Distal pancreatectomy (for tumors of the pancreatic tail) * No grossly positive surgical margins * Positive microscopic margins allowed * Nonmeasurable disease * No known CNS disease PATIENT CHARACTERISTICS: * ECOG performance status 0-1 * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception during and for 6 months after completion of study therapy * CA 19-9 ≤ 2.5 times upper limit of normal (ULN) * Absolute neutrophil count ≥ 1,500/mm³ * Hemoglobin ≥ 9 g/dL (transfusion or epoetin alfa allowed) * Platelet count ≥ 100,000/mm³ * INR ≤ 1.5 (except in patients receiving full-dose warfarin) * Bilirubin ≤ 2.0 mg/dL * AST and ALT ≤ 2.5 times ULN * Creatinine ≤ 2.0 mg/dL * No clinically significant impairment of renal function * No postoperative complications, including any of the following: * Wound dehiscence or infection * Intra-abdominal abscess * Pancreatic or biliary leak or fistula * Grade 3 or 4 delayed hemorrhage (occurring \> 5 days postoperatively) * Bowel perforation * No abdominal fistula, gastrointestinal perforation, or intra-abdominal abcess within the past 6 months * No history of major psychiatric disorder or other chronic medical illness that, in the opinion of the treating physician, contraindicates use of the study drugs or renders the patient at high risk of treatment-related complications * No other cancer within the past 5 years except basal cell or squamous cell skin cancer * No history of serious systemic disease, including any of the following: * Myocardial infarction or unstable angina within the past 12 months * New York Heart Association class II-IV congestive heart failure * Unstable symptomatic arrhythmia requiring medication * Chronic atrial arrhythmia (i.e., atrial fibrillation or paroxysmal supraventricular tachycardia) allowed * No history of stroke or transient ischemic attack * No symptomatic peripheral vascular disease * No significant vascular disease (e.g., aortic aneurysm, aortic dissection) * No inadequately controlled hypertension (i.e., blood pressure \> 150/100 mm Hg on antihypertensive medication) * No prior hypertensive crisis or hypertensive encephalopathy * No proteinuria (defined as urine protein:creatinine ratio ≥ 1.0 OR proteinuria ≥ 2+ by dipstick urinalysis OR protein \> 1 g by 24-hour urine collection) * No serious, nonhealing wound or ulcer * No evidence of bleeding diathesis or coagulopathy * No significant traumatic injury within the past 28 days PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No prior chemotherapy or radiotherapy for pancreatic cancer * No prior systemic or investigational therapy for pancreatic cancer * No major surgical procedure (except for resection of pancreatic cancer) or open biopsy within the past 28 days * No fine-needle aspiration or core biopsy within the past 7 days * No anticipated need for a major surgical procedure during study treatment * No concurrent newly prescribed nonsteroidal anti-inflammatory drugs (NSAIDs) * Concurrent chronic-dose NSAIDs for analgesia are allowed