DISEASE CHARACTERISTICS:

• Histologically confirmed intracranial glioblastoma multiforme

• Disease progression by MRI or CT scan

  • Confirmation of true progressive disease (not radiation necrosis) by positron-emission tomography, thallium scanning, MRI, or surgical documentation required if patient received prior interstitial brachytherapy or stereotactic radiosurgery
• Failed prior radiotherapy

• Phase I patients:

  • Eligible for salvage surgery
  • No limits on prior therapy

• Phase II patients:

  • Tumor progression by MRI or CT scan required within the past 14 days if recurrent disease is present
  • No prior therapy for more than 3 relapses

  • Recent resection of recurrent or progressive tumor allowed as long as all of the following conditions apply:

    • Recovered from surgery
    • MRI or CT scan performed no more than 96 hours since prior surgery OR within 4-6 weeks after surgery
    • Baseline MRI or CT scan performed within 14 days of study entry

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• Karnofsky 60-100%

Life expectancy

• More than 8 weeks

Hematopoietic

• WBC at least 3,000/mm^3
• Absolute neutrophil count at least 2,000/mm^3
• Platelet count at least 100,000/mm^3
• Hemoglobin at least 10 g/dL (transfusion allowed)

Hepatic

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

Renal

• Creatinine less than 1.5 mg/dL

Other

• Cholesterol less than 350 mg/dL
• Triglycerides less than 400 mg/dL
• No concurrent disease that would obscure toxicity or dangerously alter drug metabolism
• No other significant uncontrolled serious medical illness that would preclude study participation
• No other cancer except non-melanoma skin cancer or carcinoma in situ of the cervix unless patient is in complete remission and off all therapy for that disease for at least 3 years
• No active infection
• No prior allergic reactions to compounds of similar chemical or biological composition to sirolimus
• No psychiatric illness that would preclude study participation
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective barrier contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy

• At least 1 week since prior interferon

Chemotherapy

• At least 2 weeks since prior vincristine
• At least 3 weeks since prior procarbazine
• At least 6 weeks since prior nitrosoureas

Endocrine therapy

• At least 1 week since prior tamoxifen

Radiotherapy

• See Disease Characteristics
• At least 4 weeks since prior radiotherapy

Surgery

• See Disease Characteristics

Other

• Recovered from prior therapy
• At least 1 week since prior noncytotoxic agents (except radiosensitizers)