OUTLINE: This is a dose escalation study of gemcitabine. Part I: Patients receive gemcitabine as a continuous infusion over 30 minutes once weekly for 3 weeks followed by 1 week of rest. Part II: Gemcitabine IV is administered as a 30 minute infusion twice a week (Monday and Thursday) for 5-6 weeks. Patients receive radiation therapy 5 days a week for 5-6 weeks. In the absence of dose-limiting toxicity (DLT) in the first 6 patients treated, subsequent cohorts of 6 patients each receive escalating doses of gemcitabine on the same schedule. If DLT occurs in 2 of 6 patients at a given dose level, then dose escalation ceases and the next lower dose is declared the maximum tolerated dose. Part III: In the absence of toxicity and disease progression, patients continue gemcitabine for 3 additional courses. Maintenance gemcitabine starts 4 weeks after the completion of radiation therapy and is administered once weekly for 3 weeks followed by 1 week of rest. Patients are followed until death.