This phase III trial is studying how well radiation therapy, amifostine, and chemotherapy work in treating young patients with newly diagnosed nasopharyngeal cancer. Radiation therapy uses high-energy x-rays to kill tumor cells. Drugs, such as amifostine, may protect normal cells from the side effects of radiation therapy. Drugs used in chemotherapy, such as cisplatin and fluorouracil, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving radiation therapy together with amifostine and chemotherapy may kill more tumor cells.