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 whether radiation therapy plus cisplatin 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 radiation therapy plus cisplatin with radiation therapy alone in treating patients with head and neck cancer that has been removed during surgery.

OBJECTIVES: I. Evaluate locoregional control rates, patterns of first failure, and overall and disease-free survival in patients with advanced squamous cell carcinoma of the head and neck at high risk of locoregional recurrence who are treated postoperatively with concurrent cisplatin and radiotherapy. II. Compare the toxicity of concurrent chemoradiotherapy vs. radiotherapy alone in the postoperative setting.

OUTLINE: Randomized study. Arm I: Radiotherapy. Involved-field irradiation using Co60, 1-6 MV photons, or electrons. Arm II: Radiotherapy plus Single-Agent Chemotherapy. Irradiation as in Arm I; plus Cisplatin, CDDP, NSC-119875.

PROJECTED ACCRUAL: 438 patients will be entered over approximately 5 years.

DISEASE CHARACTERISTICS: Biopsy-proven squamous cell carcinoma of one of the following sites: Hypopharynx Larynx Oral cavity Oropharynx At least 1 of the following high-risk factors required: Histologic extracapsular nodal extension Histologic involvement of 2 or more regional lymph nodes Microscopically positive mucosal margins Complete resection of all visible and palpable disease Therapy must begin within 8 weeks of tumor-related surgery Bilateral resections may or may not be performed simultaneously Eligibility window begins with first definitive surgery Neck dissection not required for T4 N0, truly midline supraglottic tumors No tumors of the lip, nasopharynx, or sinuses No synchronous or concurrent head and neck tumors No evidence of distant metastasis Concurrent registration on Fixed Tumor Repository Study allowed

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 60%-100% Hematopoietic: WBC at least 3,500 Platelets at least 100,000 Hepatic: Not specified Renal: Creatinine clearance greater than 50 mL/min Other: No medical contraindication to protocol therapy No second malignancy within 5 years No pregnant or nursing women

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior chemotherapy Endocrine therapy: Not specified Radiotherapy: No prior radiotherapy to head and neck region Surgery: See Disease Characteristics