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.

OBJECTIVES: I. Determine whether the addition of cisplatin to high-dose postoperative radiotherapy increases the disease-free survival rate of patients with locally advanced head and neck carcinomas at high risk of recurrence following radical surgery.

OUTLINE: Randomized study. Patients are registered and randomized to treatment within 25 days of surgery. Arm I: Radiotherapy. Irradiation of the preoperative primary tumor site with a boost to areas at high risk for recurrence using Co60 equipment, 4-6 MV linear accelerators, or 6-12 MeV electrons. Arm II: Radiotherapy plus Single-Agent Chemotherapy. Irradiation as in Arm I; plus Cisplatin, CDDP, NSC-119875.

PROJECTED ACCRUAL: A total of 338 evaluable patients will be studied.

DISEASE CHARACTERISTICS: Histologically confirmed squamous cell carcinoma of the head and neck of the following sites: Oral cavity Oropharynx Hypopharynx (only if ineligible for protocol EORTC-24891) Larynx T3-4, any N, M0 or any T, N2-3, M0 disease (UICC staging) resected with curative intent T3, N0 carcinoma of the larynx with suitable microscopically clear margins is ineligible At least one of the following high-risk characteristics required: Histopathologically positive surgical margins No gross residual disease Perineural involvement Extranodal spread of disease Oral cavity or oropharyngeal lesions with metastatic nodes at level 4 or 5 Vascular embolisms in the neck No metastases at diagnosis No known CNS disease

PATIENT CHARACTERISTICS: Age: 18 to 70 Performance status: WHO 0-2 Hematopoietic: WBC at least 4,000 Platelets at least 100,000 Hemoglobin normal (at least 6.8 mmoles/liter) Hepatic: Bilirubin no greater than 2 times normal Other liver function tests no greater than 2 times normal Renal: Creatinine no greater than 1.3 mg/dL (120 micromoles/liter) Creatinine clearance greater than 60 mL/min Other: No active, uncontrolled infection No requirement for antibiotics that might interfere with platinum excretion No requirement for drugs affecting bone marrow function (e.g., lithium, corticosteroids) No medical condition precluding postoperative chemotherapy No prior or concurrent malignancy other than nonmelanomatous skin cancer

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior chemotherapy Endocrine therapy: Not specified Radiotherapy: No prior locoregional radiotherapy to the head and neck Surgery: Excision with curative intent required