RATIONALE: Radiation therapy uses high-energy x-rays to damage tumor cells. Drugs such as tamoxifen may make the tumor cells more sensitive to radiation therapy.

PURPOSE: Phase II trial to study the effectiveness of combining radiation therapy with tamoxifen in treating patients who have newly diagnosed supratentorial glioblastoma multiforme.

OBJECTIVES: I. Determine whether high-dose tamoxifen initiated at the beginning of conventional radiotherapy improves the median survival time of adults with newly diagnosed, supratentorial glioblastoma multiforme. II. Determine the feasibility and toxicity of high-dose tamoxifen in these patients. III. Determine the overall survival with respect to protein kinase C lab correlates in patients treated with this regimen.

OUTLINE: This is a multicenter study. Beginning within 5 weeks after surgery, patients undergo radiotherapy to the brain 5 days a week for 6 weeks. Patients receive high-dose oral tamoxifen every 6 hours beginning on day 1 of radiotherapy and continuing in the absence of disease progression. Patients are followed every 3 months through year 1, every 4 months for 1 year, every 6 months for 2 years, and then annually thereafter.

PROJECTED ACCRUAL: A total of 72 patients will be accrued for this study within 6 months.

DISEASE CHARACTERISTICS: Histologically proven newly diagnosed, supratentorial glioblastoma multiforme (with areas of necrosis) Diagnosis must be made by surgical biopsy or excision within the past 5 weeks No recurrent malignant gliomas No metastases below the tentorium or beyond the cranial vault

PATIENT CHARACTERISTICS: Age: Adult Performance status: Karnofsky 70-100% OR Zubrod 0-1 Life expectancy: At least 8 weeks Hematopoietic: Hemoglobin at least 10 g/dL (transfusion allowed) Hematocrit at least 30% (transfusion allowed) Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 2.0 mg/dL serum glutamate pyruvate transaminase (SGPT) or serum glutamate oxaloacetate transaminase (SGOT) no greater than 2 times normal Renal: Blood urea nitrogen no greater than 25 mg/dL Creatinine no greater than 1.5 mg/dL Cardiovascular: No active thrombophlebitis Other: Recovered from any postoperative infection or other complications No major medical illnesses or psychiatric impairments that would preclude study participation No active connective tissue disorder, such as lupus or scleroderma No other malignancy within the past 5 years except nonmelanomatous skin cancer or carcinoma in situ of the cervix or bladder No prior endometrial cancer or atypical endometrial hyperplasia No AIDS Not pregnant or nursing Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Not specified Endocrine therapy: At least 12 months since prior tamoxifen Radiotherapy: See Disease Characteristics No prior radiotherapy to head or neck Surgery: See Disease Characteristics Recovered from prior surgery