Tamoxifen, Carboplatin, and Topotecan in Treating Patients With CNS Metastases or Recurrent Brain or Spinal Cord Tumors

DISEASE CHARACTERISTICS: * Diagnosis of 1 of the following: * Epithelial neoplasms metastatic to the central nervous system * Recurrent or refractory to prior chemotherapeutic or radiotherapeutic regimens or for which no standard chemotherapy or whole brain radiotherapy regimens exist * Stage IV disease * Recurrent glial tumors (brain or spinal cord) * Received prior whole brain radiotherapy or stereotactic radiotherapy OR refused radiotherapy * Patients with CNS metastases previously treated with radiotherapy are eligible, provided persistent or progressive CNS metastases are documented by MRI eight weeks after the end of radiotherapy * Patients with glial tumors must show progressive disease by MRI after prior radiotherapy * Measurable disease in the brain/leptomeninges of the brain or spinal cord with baseline documentation within 4 weeks of study entry * Must have ≥ 1 lesion that is ≥ 1 cm on MRI scan * Ineligible for or has refused participation in higher priority institutional protocols PATIENT CHARACTERISTICS: * Karnofsky performance status 50-100% * Life expectancy ≥ 2 months * Creatinine ≤ 1.5 mg/dL * WBC 4,000/mm³ OR ANC ≥ 2,000/mm³ * Platelet count ≥ 150,000/mm³ * Bilirubin ≤ 1.5 mg/dL * ALT and AST \< 2 times upper limit of normal * Not pregnant * Negative pregnancy test * Fertile patients must use effective contraception * No nonmalignant concurrent illness (e.g., cardiovascular or pulmonary) that is either poorly controlled with currently available treatment or of such severity to preclude study entry * No severe infection * Patients who are ineligible for lumbar puncture are allowed PRIOR CONCURRENT THERAPY: * See Disease Characteristics * At least 3 weeks since prior radiotherapy, immunotherapy, or chemotherapy OR recovered from expected side effects of prior therapy * No patients who are recovering from major surgery * No concurrent radiotherapy * Concurrent steroid or anticonvulsant therapy allowed