Temozolomide in Treating Patients With Leptomeningeal Metastases From a Solid Tumor or Lymphoma

* Documented leptomeningeal metastases * Carcinomatous meningitis that is previously untreated or failed prior therapy OR * Lymphomatous meningitis * Systemic disease that is responding or stable on current therapy not eligible if discontinuing therapy would be deleterious * Age 18 and over * Karnofsky Performance Status 60-100% * Life expectancy of at least 6 weeks * Absolute neutrophil count greater than 1,500/μL * Platelet count greater than 100,000/μL * Creatinine no greater than 2.0 mg/dL * No congestive heart failure * No unstable angina * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No contraindication to diagnostic sampling of CSF via lumbar puncture or reservoir * No medical conditions that would interfere with absorption of oral medication (e.g., malabsorption, obstruction, or frequent vomiting) * No uncontrolled infection * Prior neuroaxis chemotherapy (lumbar puncture, reservoir, or systemic) allowed * No other concurrent chemotherapy for other sites of disease * No prior radiotherapy to areas of measurable meningeal disease unless there is clear radiographic progression in these areas * No prior radiotherapy to greater than 30% of bone marrow * Prior radiotherapy to the neuroaxis allowed * No concurrent radiotherapy for other sites of disease or for progressive disease * Recovered from any prior recent therapy