 RATIONALE: Drugs used in chemotherapy, such as capecitabine and oxaliplatin, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Radiation therapy uses high-energy x-rays to kill tumor cells. Oxaliplatin may make tumor cells more sensitive to radiation therapy. Giving capecitabine and oxaliplatin together with radiation therapy before surgery may shrink the tumor so it can be removed. 