Busulfan in Treating Children and Adolescents With Refractory CNS Cancer

DISEASE CHARACTERISTICS:

* Histologically confirmed CNS malignancy, including any of the following:

  * Primary malignant brain tumor refractory to standard therapy and metastatic to the cerebrospinal fluid (CSF) or leptomeningeal subarachnoid space
  * Recurrent or persistent leptomeningeal leukemia, lymphoma, or germ cell tumor refractory to conventional therapy

    * In second or greater relapse
    * CSF white blood count greater than 5 cells/mm3 with blasts on cytospin OR
    * Evidence of leptomeningeal tumor by MRI
* No concurrent bone marrow disease
* No obstruction or compartmentalization of CSF flow on CSF flow study

PATIENT CHARACTERISTICS:

Age:

* 3 to 21

Performance status:

* Lansky 50-100% (under 10 years)
* Karnofsky 50-100% (10 to 21 years)

Life expectancy:

* Greater than 8 weeks

Hematopoietic:

* Absolute neutrophil count greater than 1,000/mm\^3
* Platelet count greater than 75,000/mm\^3

Hepatic:

* Bilirubin normal for age
* ALT and AST less than 5 times upper limit of normal (ULN)
* No hepatic disease

Renal:

* Creatinine no greater than 1.5 times ULN OR
* Glomerular filtration rate greater than 70 mL/min
* No renal disease

Cardiovascular:

* No cardiac disease

Pulmonary:

* No pulmonary disease

Other:

* No uncontrolled infection
* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

* Not specified

Chemotherapy:

* At least 3 weeks since prior myelosuppressive chemotherapy (6 weeks for nitrosoureas)
* At least 1 week since prior intrathecal chemotherapy (2 weeks for cytarabine) and recovered
* Evidence of subsequent disease progression
* Concurrent systemic chemotherapy allowed for recurrent disease after first course of treatment except for the following:

  * Chemotherapy targeted at leptomeningeal disease
  * Other phase I agent
  * Any agent that significantly penetrates the CSF (e.g., high dose methotrexate greater than 1 g/m2, thiotepa, high dose cytarabine, fluorouracil, IV mercaptopurine, nitrosoureas, or topotecan)
  * Any agent that causes serious unpredictable CNS side effects

Endocrine therapy:

* Prior dexamethasone allowed with decreasing or stable dose at least one week before study
* Concurrent dexamethasone or prednisone with chemotherapy regimen allowed

Radiotherapy:

* At least 1 week since prior focal irradiation to the brain or spine
* At least 8 weeks since prior craniospinal irradiation
* No concurrent cranial or craniospinal irradiation

Surgery:

* Not specified

Other:

* No other concurrent intrathecal or systemic therapy for leptomeningeal disease