Temozolomide and Radiation Therapy in Treating Patients With Stage IV Malignant Melanoma With Measurable and Unresectable Cancer of the Central Nervous System

DISEASE CHARACTERISTICS: Histologically confirmed stage IV malignant melanoma with measurable and unresectable disease limited to the central nervous system (CNS) Study entry within 14 days of diagnosis of brain metastases Recursive partitioning analysis class I or II Disease for which no known standard therapy exists that is potentially curative or proven capable of extending life expectancy No meningeal carcinomatosis based on imaging studies or on positive results from CSF analysis No evidence of metastatic disease outside of the CNS PATIENT CHARACTERISTICS: Age 18 and over Performance status Karnofsky 70-100% Hematopoietic Absolute neutrophil count at least 1,500/mm^3 Platelet count at least 100,000/mm^3 Hemoglobin at least 9.0 g/dL Hepatic AST no greater than 3 times upper limit of normal (ULN) Alkaline phosphatase no greater than 3 times ULN Renal Creatinine no greater than 1.5 times ULN Other Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No concurrent uncontrolled infection No other malignancy within the past 5 years except basal cell or squamous cell skin cancer treated with local resection only No prior allergy or intolerance to dacarbazine No hypersensitivity to temozolomide or any of its components PRIOR CONCURRENT THERAPY: Biologic therapy More than 4 weeks since prior biologic therapy More than 4 weeks since prior immunotherapy Chemotherapy No prior temozolomide More than 4 weeks since prior chemotherapy (6 weeks for mitomycin or nitrosoureas) and recovered Endocrine therapy Concurrent steroids allowed if dose stable for at least 7 days prior to CNS imaging Radiotherapy More than 4 weeks since prior radiotherapy No prior radiotherapy to more than 15% of the bone marrow No prior radiotherapy to the head and neck area No prior radiosurgery