Capecitabine, Bevacizumab, and Radiation Therapy Followed By Gemcitabine and Bevacizumab in Treating Patients With Locally Advanced Pancreatic Cancer That Cannot Be Removed By Surgery

Inclusion Criteria: * Histologically confirmed adenocarcinoma of the pancreas * Locally advanced disease * Unresectable disease * All malignant disease must be encompassable within a single irradiation field * Radiographically assessable disease * Patients with biliary or gastroduodenal obstruction are eligible provided drainage or surgical bypass was performed prior to initiation of study treatment * No evidence of gastric outlet obstruction * No evidence of duodenal invasion on CT scan * No evidence of metastatic disease in the major viscera * No peritoneal seeding or ascites * Performance status - Zubrod 0-1 * Granulocyte count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 * No evidence of bleeding diathesis * ALT \< 3 times upper limit of normal * Bilirubin \< 2.0 mg/dL * INR ≤ 1.5 * No evidence of coagulopathy * Creatinine clearance \> 50 mL/min * Urine protein \< 1,000 mg by 24-hour urine collection (for patients with proteinuria ≥ 1+ by dipstick or urinalysis OR urine protein:creatinine ratio ≥ 1.0) * No myocardial infarction within the past 6 months * No unstable angina within the past 6 months * No arterial thromboembolic events within the past 6 months, including any of the following: * Transient ischemic attack * Cerebrovascular accident * Clinically significant peripheral artery disease * No unstable symptomatic arrhythmia requiring medication (e.g., chronic atrial arrhythmia \[i.e., atrial fibrillation or paroxysmal supraventricular tachycardia\]) * Patients with an atrial arrhythmia are eligible provided the condition is well controlled on stable medication * No New York Heart Association class II-IV congestive heart failure * No history of arteriovenous malformation * No history of aneurysm * No uncontrolled hypertension (i.e., blood pressure \> 160/90 mm Hg with medication) * No other clinically significant cardiac disease * No AIDS * No significant infection * No known hypersensitivity to Chinese hamster ovary cell products or other recombinant human antibodies * Not pregnant * No nursing during and for ≥ 3-4 months after completion of study treatment * Negative pregnancy test * Fertile patients must use effective contraception during and for ≥ 3-4 months after completion of study treatment * No history of gastrointestinal fistula or perforation * No other malignancy within the past two years except nonmelanoma skin cancer or carcinoma in situ of the cervix, uterus, or bladder * No significant traumatic injury within the past 4 weeks * No serious nonhealing wound or ulcer * No current healing fracture * No known or suspected dihydropyrimidine dehydrogenase deficiency * No other medical condition that would preclude study participation * No concurrent interleukin-11 * No prior chemotherapy for pancreatic cancer * More than 2 years since prior chemotherapy for another malignancy * No prior radiotherapy to the planned irradiation field * No concurrent intensity modulated radiotherapy * No other concurrent radiotherapy * See Disease Characteristics * More than 4 weeks since prior major surgical procedure or open biopsy * More than 1 week since prior fine needle aspiration or core biopsy * No prior organ transplantation * No concurrent major surgical procedure * More than 30 days since prior and no concurrent cimetidine * Concurrent ranitidine or a drug from another anti-ulcer class allowed * More than 4 weeks since prior and no concurrent sorivudine or brivudine * No concurrent warfarin during chemoradiotherapy * Concurrent warfarin allowed beginning 2 weeks after completion of chemoradiotherapy * Concurrent low molecular weight heparin allowed (at any time during study participation) * No other concurrent investigational agents * No other concurrent cytotoxic agents