Pemetrexed Disodium in Treating Patients With Recurrent Malignant Gliomas, Primary CNS Lymphoma, or Brain Metastases

DISEASE CHARACTERISTICS: Diagnosis of 1 of the following: Malignant glioma, including the following subtypes: glioblastoma or gliosarcoma, anaplastic astrocytoma, anaplastic oligodendroglioma, anaplastic mixed glioma, or malignant glioma not otherwise specified, meeting the following criteria: Not required to have measurable or evaluable disease Must have failed prior radiation therapy > 4 weeks ago Must have failed at least 1 prior chemotherapy regimen Confirmation of tumor progression by MR spectroscopy, PET scan, or biopsy/resection if prior radiosurgery was performed Primary CNS lymphoma, meeting the following criteria: Measurable disease as defined by bidimensionally measurable lesions with clearly defined margins by CT scan or MRI Must have failed at least one prior chemotherapy regimen Must have failed at least one agent or regimen Brain metastases from a solid tumor, meeting the following criteria: Measurable disease as defined by bidimensionally measurable lesions with clearly defined margins by CT scan or MRI Biopsy is not required if radiographic imaging is consistent with brain metastases Must have failed prior whole-brain radiotherapy Patients with leptomeningeal metastases with or without brain metastases are eligible for therapy (may be diagnosed by MRI or cytology) Confirmation of tumor progression by MR spectroscopy, PET scan, or biopsy/resection if prior radiosurgery was performed Effusions or fluid collections must be drained prior to study entry PATIENT CHARACTERISTICS: Karnofsky performance score ≥ 60 WBC > 3,000/mm^3 Absolute neutrophil count > 1,500/mm^3 Platelet count > 100,000/mm^3 Hemoglobin > 10 mg/dL (transfusion allowed) SGOT/SGPT < 3.0 times upper limit of normal (ULN) Bilirubin < 1.5 times ULN Creatinine < 1.5 mg/dL Creatinine clearance > 45 mL/min Women of childbearing potential and sexually active males must commit to the use of effective contraception while on study and for 3 months after completing study treatment Women who are pregnant or breast-feeding are not eligible for study treatment Negative pregnancy test Able to take steroids, vitamin B12, or folate No significant medical illnesses or infection that, in the investigator's opinion, cannot be adequately controlled with appropriate therapy or would compromise the patient's ability to tolerate this therapy Only one active tumor type allowed, except nonmelanoma skin cancer or carcinoma in situ of the cervix A history of other malignancies are acceptable if in complete remission and off all therapy for that disease for a minimum of 3 years PRIOR CONCURRENT THERAPY: See Disease Characteristics More than 4 weeks since prior whole-brain or other radiotherapy Recovered from any side effects (6 weeks for a nitrosourea; 4 weeks for temozolomide, procarbazine, etoposide or experimental agent; 3 weeks for isotretinoin or tamoxifen) (for patients with gliomas) No more than 2 prior chemotherapeutic agents or regimens (includes biologic agents) (for patients with gliomas) Recovered from prior biopsy or re-resection of the tumor (10-14 days for resection or 3-5 days for a biopsy) (for patients with gliomas) May not be on any other chemotherapy except for hormonal therapy or trastuzumab (Herceptin®) (for patients with brain metastases) No limitations on prior CNS-directed therapies (for patients with brain metastases) Able to discontinue nonsteroidal anti-inflammatory drugs (NSAIDs) Patients taking NSAIDs or aspirin are required to interrupt therapy for at least 2 days before the study treatment and 2 days after the infusion