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