Testing the Addition of a Radiation Sensitizing Drug, IPdR, to the Usual Chemotherapy Treatment (Capecitabine) During Radiation Therapy for Rectal Cancer

This phase I trial studies the side effects and best dose of ropidoxuridine and how well it works when added to the usual chemotherapy treatment (capecitabine) during radiation therapy for the treatment of patients with stage II-III rectal cancer. Ropidoxuridine may help radiation therapy work better by making cancer cells more sensitive to the radiation therapy. Chemotherapy drugs, such as capecitabine, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Radiation therapy uses high energy x-rays to kill tumor cells and shrink tumors. This study is being done to find out whether ropidoxuridine in addition to capecitabine and radiation therapy works better in treating patients with rectal cancer.