RATIONALE: 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. Radiation therapy uses high-energy x-rays to kill tumor cells. Vandetanib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. It is not yet known whether giving chemotherapy together with radiation therapy is more effective with or without vandetanib in treating patients with head and neck cancer.