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