RATIONALE: Giving radiation therapy that uses a 3-dimensional (3-D) image of the tumor to help focus thin beams of radiation directly on the tumor, and giving radiation therapy in higher doses over a shorter period of time, may kill more tumor cells and have fewer side effects. 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 when given alone or together with cetuximab in treating patients with head and neck cancer that has been removed by surgery.