RATIONALE: Radiation therapy uses high-energy x-rays to kill tumor cells and shrink tumors. Drugs used in chemotherapy, such as cisplatin, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. 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. It is not yet known whether radiation therapy is more effective with cisplatin or cetuximab in treating oropharyngeal cancer. PURPOSE: This phase III trial is studying radiation therapy with cisplatin or cetuximab to see how well it works in treating patients with oropharyngeal cancer. (NCT01302834)