OBJECTIVES: I. Determine the maximum tolerated dose of gemcitabine in combination with radiation therapy to patients with locally advanced and/or unresectable adenocarcinoma of the pancreas. II. Determine the dose limiting toxic effects of this combination therapy in these patients. III. Evaluate the ability of these patients to tolerate induction and then maintenance therapy with gemcitabine preceding and following combination therapy. IV. Evaluate the efficacy (response rate, pattern of failure, and survival) of this combination therapy in these patients.