OUTLINE: This is a dose-escalation study of capecitabine. Patients receive oral capecitabine twice a day 7 days a week for 6 weeks with concurrent radiotherapy. Radiotherapy is initiated on the same day as the initiation of capecitabine and is administered 5 days a week for 5.5-6 weeks. Cohorts of 3-6 patients receive escalating doses of capecitabine until the maximum tolerated dose (MTD) is reached. The MTD is defined as the dose at which 2 of 3 or 6 patients experience dose-limiting toxicity. Patients are followed every 3 months for 2 years and then every 6 months for 1 year.