MDX-010 in Treating Patients With Stage IV Pancreatic Cancer That Cannot Be Removed By Surgery

DISEASE CHARACTERISTICS: * Histologically confirmed pancreatic adenocarcinoma * Stage IV disease * Locally (invasion of adjacent structures, including mesenteric arteries or organs) or distantly metastatic disease * Unresectable disease * Pancreatic adenocarcinoma with intraductal papillary mucinous neoplasm allowed * The following diagnoses are not allowed: * Acinar cell carcinoma * Pancreaticoblastoma * Malignant cystic neoplasms * Endocrine neoplasms * Squamous cell carcinoma * Vater and periampullary duodenal or common bile duct malignancies * Clinically evaluable disease with ≥ 1 site of measurable disease * Biliary or gastric outlet obstruction allowed provided it is effectively drained by endoscopic, operative, or interventional means * Pancreatic, biliary, or enteric fistulae allowed provided they are controlled with an appropriate drain PATIENT CHARACTERISTICS: Age * 18 and over Performance status * ECOG 0-2 Life expectancy * At least 3 months Hematopoietic * WBC ≥ 2,500/mm\^3 * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 * Hemoglobin ≥ 9 g/dL * Hematocrit ≥ 27% Hepatic * Hepatitis B surface antigen negative * Hepatitis C virus antibody negative OR * Hepatitis C RNA negative by polymerase chain reaction Renal * Creatinine \< 2.0 mg/dL Immunologic * HIV negative * No history of or active autoimmune disease, including uveitis or autoimmune inflammatory eye disease * No active uncontrolled infection Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, superficial bladder cancer, or carcinoma in situ of the cervix * No underlying medical condition that would preclude study participation PRIOR CONCURRENT THERAPY: Biologic therapy * No prior anti-cytotoxic T-lymphocyte-associated antigen-4 monoclonal antibody (MDX-010) Chemotherapy * At least 3 weeks since prior chemotherapy for pancreatic adenocarcinoma and recovered * No concurrent chemotherapy Endocrine therapy * More than 4 weeks since prior corticosteroids * No concurrent systemic or topical corticosteroids Radiotherapy * At least 3 weeks since prior radiotherapy for pancreatic adenocarcinoma and recovered Surgery * See Disease Characteristics Other * At least 3 weeks since other prior therapy for pancreatic adenocarcinoma and recovered * No concurrent immunosuppressants (e.g., cyclosporin or its analog)