RATIONALE: Drugs used in chemotherapy, such as oxaliplatin and capecitabine, 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. Monoclonal antibodies, such as cetuximab, can block tumor growth in different ways. Some block the ability of tumor cells to grow and spread. Others find tumor cells and help kill them or carry tumor-killing substances to them. Giving chemotherapy and radiation therapy with or without cetuximab before surgery may make the tumor smaller and reduce the amount of normal tissue that needs to be removed. It is not yet known whether giving oxaliplatin, capecitabine, and radiation therapy is more effective with or without cetuximab when given before surgery in treating rectal cancer.