- All patients will receive the same two chemotherapy drugs and radiation therapy. Both gemcitabine and 5-fluorouracil will begin on the first week of radiation therapy. 5-fluorouracil will be given continuously by intravenous infusion and will continue until the external beam radiation therapy is completed. The gemcitabine will be given (at different doses for each cohort of patients) once per week for seven weeks. Radiation therapy will be given daily for five days for seven weeks. On those days when gemcitabine is given, radiation therapy will be given approximately four hours after the gemcitabine dose.