Flavopiridol Plus Radiation Therapy Followed By Gemcitabine Hydrochloride in Treating Patients With Locally Advanced, Unresectable Pancreatic Cancer

Inclusion Criteria: * Histologically or cytologically confirmed adenocarcinoma of the pancreas * No non-adenocarcinoma of the pancreas (i.e., islet cell, lymphoma, or sarcoma) * Locally advanced and unresectable disease defined as the following: * Obvious encasement of the celiac, hepatic, or superior mesenteric artery * Encasement of the portal or superior mesenteric vein not amenable to resection * Extrapancreatic extension with or without regional lymph node involvement * No distant metastases * Measurable or evaluable disease * Primary pancreatic tumor is considered evaluable, not measurable * A lymph node mass is considered measurable * Performance status - ECOG 0-2 * Performance status - Karnofsky 60-100% * More than 12 weeks * WBC at least 3,000/mm\^3 * Absolute neutrophil count at least 1,500/mm\^3 * Platelet count at least 100,000/mm\^3 * Bilirubin no greater than 1.5 mg/dL * AST and ALT no greater than 2.5 times upper limit of normal * Creatinine no greater than 1.5 mg/dL * Creatinine clearance at least 60 mL/min * No symptomatic congestive heart failure * No unstable angina pectoris * No cardiac arrhythmia * No Crohn's disease or inflammatory bowel disease that would preclude study participation * No gastrointestinal tract disease resulting in an inability to take oral medication or a requirement for IV alimentation * No other uncontrolled concurrent illness that would preclude study participation * No ongoing or active infection * No ps…