Erlotinib, Gemcitabine, and Radiation Therapy in Treating Patients With Locally Advanced Unresectable Pancreatic Cancer

Inclusion Criteria: * Histologically or cytologically confirmed adenocarcinoma of the pancreas * Locally advanced, unresectable disease, defined by all of the following: * Obvious encasement of the celiac, hepatic, or superior mesenteric artery * Encasement of the portal or superior mesenteric vein not amenable to surgical resection * Extrapancreatic extension with or without regional lymph node involvement * No evidence of distant metastatic disease by staging laparoscopy\* * Locally recurrent disease after prior curative surgery allowed provided the following are true: * No prior chemotherapy or radiotherapy * No evidence of distant metastatic disease by staging laparoscopy\* * No islet cell pancreatic cancer or lymphoma or sarcoma of the pancreas * Measurable or evaluable disease * Primary pancreatic tumor is considered evaluable and not measurable disease * Lymph node mass considered measurable disease * No known brain metastases * Performance status - ECOG 0-2 * More than 12 weeks * WBC ≥ 3,000/mm\^3 * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 * Bilirubin ≤ 1.5 mg/dL * AST and ALT ≤ 2.5 times upper limit of normal * Creatinine ≤ 2.0 mg/dL * Creatinine clearance ≥ 60 mL/min * No symptomatic congestive heart failure * No unstable angina pectoris * No cardiac arrhythmia * No abnormalities of the cornea based on history (e.g., dry eye syndrome or Sjögren's syndrome) * No congenital abnormality (e.g., Fuch's …