DISEASE CHARACTERISTICS:

• Histologically proven recurrent primary malignant glioma

  • Measurable recurrent or residual primary central nervous system neoplasm confirmed by MRI

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance Status:

• Karnofsky at least 60%

Hematopoietic:

• Hematocrit greater than 29%
• ANC greater than 1,500/mm^3
• Platelet count greater than 125,000/mm^3

Hepatic:

• SGOT less than 1.5 times upper limit of normal (ULN)
• Bilirubin less than 1.5 times ULN

Renal:

• Creatinine less than 1.5 mg/dL
• BUN less than 25 mg/dL

Other:

• Not pregnant
• Effective contraceptive method must be used for the duration of the study

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• Not specified

Chemotherapy:

• No prior chemotherapy within 6 weeks of study
• No prior topotecan or carmustine treatment failure
• No more than 1 prior chemotherapy regimen

Endocrine therapy:

• Patients taking corticosteroids must be on stable dose for at least 2 weeks prior to study and the dose should not escalate over entry level

Radiotherapy:

• No prior radiotherapy within 6 weeks of study

Surgery:

• No prior surgical resection within 3 weeks of study

Other:

• No concurrent medication that may interfere with study results