Fluorouracil, External-Beam Radiation Therapy, and Gemcitabine With or Without Brachytherapy Using Phosphorus P32 in Treating Patients With Locally or Regionally Advanced Unresectable Adenocarcinoma of the Pancreas

RATIONALE: Drugs used in chemotherapy, such as fluorouracil and gemcitabine, work in different ways to stop tumor cells from dividing so they stop growing or die. Radiation therapy uses high-energy x-rays to damage tumor cells. Fluorouracil may make the tumor cells more sensitive to radiation therapy. Brachytherapy uses radioactive material, such as phosphorus P32, placed directly into or near a tumor to kill tumor cells. Combining chemotherapy and external-beam radiation therapy with brachytherapy may kill more tumor cells. PURPOSE: This randomized clinical trial is studying fluorouracil, gemcitabine, external-beam radiation therapy, and brachytherapy using phosphorus P32 to see how well they work compared to fluorouracil, gemcitabine, and external-beam radiation therapy in treating patients with locally or regionally advanced unresectable adenocarcinoma of the pancreas (pancreatic cancer).