Gemcitabine Plus Radiation Therapy in Treating Patients With Pancreatic Cancer

DISEASE CHARACTERISTICS: Histologically confirmed adenocarcinoma of the pancreas Locoregional and not amenable to surgery based on 1 or more of the following: Size of pancreatic tumor greater than 5 cm Lymph nodes bulky, greater than 2 cm, but within radiation port Vascular involvement or impingement of major vessels (e.g., superior mesenteric artery, superior mesenteric vein, portal vein, hepatic artery) Involvement of colon (head lesions) or involvement of adrenal, kidney, or colon (tail lesions) Patients must be registered and begin treatment within 42 days of surgical staging No metastatic disease or nodal disease outside of radiation port documented by CT scan or MRI and chest x-ray PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: Not specified Hematopoietic: Granulocyte count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Albumin greater than 3 g/dL Bilirubin less than 2.0 mg/dL Renal: Creatinine less than 2.0 mg/dL Calcium normal Other: No prior or concurrent malignancy within the past 5 years except inactive nonmelanoma skin cancer, carcinoma in situ of the cervix, or other curatively treated cancers Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: No prior biologic therapy for carcinoma of the pancreas Chemotherapy: No prior chemotherapy for carcinoma of the pancreas No other concurrent chemotherapy Endocrine therapy: No prior endocrine therapy for carcinoma of the pancreas No concurrent hormone therapy (except for nondisease-related conditions) Radiotherapy: No prior radiation therapy for carcinoma of the pancreas No prior abdominal radiation therapy Surgery: See Disease Characteristics No prior surgery for carcinoma of the pancreas