Gemcitabine and Radiation Therapy in Treating Patients With Locally Advanced Upper Gastrointestinal Cancer

DISEASE CHARACTERISTICS: * Diagnosis of any of the following upper gastrointestinal malignancies: * Localized pancreatic adenocarcinoma * Stage I, II, or III disease * Parapancreatic node involvement and locally recurrent disease allowed * Locally advanced biliary, gallbladder, or ampullary adenocarcinoma * Stage II, III, or locally recurrent disease * Histologically confirmed locally advanced gastric adenocarcinoma * T3, T4, or node positive OR locally recurrent disease * Histologically confirmed locally advanced duodenal cancer * Stage II or III disease * Locally advanced, but unresectable cancers may be included on protocol if appropriate for intraoperative radiotherapy (IORT) * Other histologies may be considered for this protocol except for lymphoma, sarcoma, or neuroendocrine tumors * Patients with evidence of metastatic disease are eligible if there is significant local disease warranting surgery and IORT PATIENT CHARACTERISTICS: * Karnofsky performance status \> 60% * Life expectancy \> 4 months * Absolute neutrophil count \> 1,500/mm\^3 * Platelet count \> 100,000/mm\^3 * Serum creatinine \< 2.0 mg/dL * ALT \< 3 x normal * Bilirubin \< 2 x normal * Must be able to give voluntary informed consent * No severe intercurrent illness that would make the patient inappropriate for laparotomy or otherwise inappropriate for treatment on protocol * Prior history of malignancy allowed PRIOR CONCURRENT THERAPY: * More than 4 weeks since prior…