High-Dose Radiation Therapy With or Without Chemotherapy in Treating Patients With Head and Neck Cancer

RATIONALE: Radiation therapy uses high-energy x-rays to damage tumor cells. Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. It is not yet known if radiation therapy plus chemotherapy is more effective than radiation therapy alone in treating patients with head and neck cancer. PURPOSE: Randomized phase III trial to compare the effectiveness of high-dose radiation therapy alone with high-dose radiation therapy plus cisplatin in treating patients with head and neck cancer who have undergone surgery to remove the cancer.