DISEASE CHARACTERISTICS:

• Clinical diagnosis* of neurofibromatosis type 1 (NF1), according to NIH Consensus Conference criteria, with plexiform neurofibromas (PN) AND at least 1 of the following diagnostic criteria for NF1:

  • Six or more café-au-lait spots (≥ 0.5 cm in prepubertal patients or ≥ 1.5 cm in postpubertal patients)
  • Freckling in the axilla or groin
  • Optic glioma
  • Two or more Lisch nodules
  • Distinctive bony lesion (dysplasia of the sphenoid bone or dysplasia or thinning of long bone cortex)
  • First-degree relative with NF1 NOTE: *Histologic confirmation of tumor not required in the presence of consistent clinical and radiographic findings, but should be considered if malignant degeneration of a PN is clinically suspected

• Inoperable PN that has the potential to cause significant morbidity including, but not limited to, any of the following:

  • Head and neck lesions that could compromise the airway or great vessels
  • Brachial or lumbar plexus lesions that could cause nerve compression and loss of function
  • Lesions that could result in major deformity (e.g., orbital lesions) or significant cosmetic problems
  • Lesions of the extremity that cause limb hypertrophy or loss of function
  • Painful lesions
• Complete resection of a PN with acceptable morbidity is not feasible OR patient refuses surgery

• Measurable PN amenable to volumetric MRI analysis

  • Measurable lesion is defined as a lesion that measures at least 3 cm in one dimension

• Meets 1 of the following criteria:

  • Progressive PN, as defined by 1 of the following (stratum 1):

    • Presence of new PN on MRI or CT scan
    • Measurable increase of the PN (≥ 20% increase in the volume, ≥ 13% increase in the product of the two longest perpendicular diameters, or ≥ 6% increase in the longest diameter) on the last two consecutive MRI or CT scans or over a time period of approximately 1 year prior to study entry
  • PN without documented radiographic progression (stratum 2)
• No evidence of active optic glioma, malignant glioma, malignant peripheral nerve sheath tumor, or other cancer requiring treatment with chemotherapy or radiotherapy

PATIENT CHARACTERISTICS:

• Karnofsky performance status (PS) 50-100% (for patients > 10 years of age)
• Lansky PS 50-100% (for patients ≤ 10 years of age)
• ANC ≥ 1,500/μL
• Platelet count ≥ 100,000/μL (transfusion independent)
• Hemoglobin ≥ 10.0 g/dL (RBC transfusions allowed)

• Creatinine clearance or radioisotope glomerular filtration rate ≥ 70 mL/min OR creatinine normal based on age as follows:

  • No greater than 0.8 mg/dL (for patients 5 years of age and under)
  • No greater than 1.0 mg/dL (for patients 6-10 years of age)
  • No greater than 1.2 mg/dL (for patients 11-15 years of age)
  • No greater than 1.5 mg/dL (for patients over 15 years of age)
• Bilirubin ≤ 1.5 times upper limit of normal (ULN)
• ALT ≤ 5 times ULN
• Serum albumin ≥ 2 g/dL

• Fasting LDL cholesterol < 160 mg/dL

  • Cholesterol-lowering agent allowed, provided patient is on a single medication and has been on a stable dose for ≥ 4 weeks
• No dental braces or prosthesis that interferes with volumetric analysis of the neurofibromas

• No other concurrent severe and/or uncontrolled medical disease that could compromise participation in the study, including any of the following:

  • Uncontrolled diabetes
  • Uncontrolled hypertension
  • Uncontrolled or severe infection
  • Severe malnutrition
  • Chronic liver or renal disease
  • Active upper gastrointestinal tract ulceration

• No known history of HIV seropositivity or known immunodeficiency

  • HIV testing required only if HIV is clinically suspected

• No impairment of gastrointestinal function or gastrointestinal disease that may significantly alter the absorption of sirolimus, including any of the following:

  • Ulcerative disease
  • Uncontrolled nausea, vomiting, or diarrhea
  • Malabsorption syndrome
• Nasogastric tube allowed
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 3 months after completion of study therapy
• No history of noncompliance with medical regimens
• Willing or able to comply with the study protocol, or able to comply with the safety monitoring requirements of the study, in the opinion of the investigator

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• Recovered from all prior chemotherapy or radiotherapy
• Prior surgery for progressive PN allowed, provided the PN was incompletely resected and is measurable
• No prior small bowel resection
• No prior treatment with an mTOR inhibitor
• At least 6 months since prior involved field radiotherapy to the index PN
• At least 6 weeks since prior radiotherapy to areas outside the index PN
• At least 2 weeks since prior major surgery
• More than 4 weeks since prior myelosuppressive chemotherapy
• More than 4 weeks since prior investigational drugs
• At least 14 days since prior antineoplastic biologic agents
• At least 7 days since prior hematopoietic growth factor support

• More than 1 week since prior and no concurrent strong CYP3A4 inhibitors, including any of the following:

  • Clarithromycin
  • Telithromycin
  • Erythromycin
  • Troleandomycin
  • Cisapride
  • Metoclopramide
  • Itraconazole
  • Ketoconazole
  • Fluconazole
  • Voriconazole
  • Clotrimazole
  • Verapamil
  • Diltiazem
  • Nicardipine
  • Rifampin
  • Bromocriptine
  • Cimetidine
  • Danazol
  • Cyclosporine oral solution
  • Grapefruit juice

• More than 1 week since prior and no concurrent strong CYP3A4 inducers, including any of the following:

  • Carbamazepine (Tegretol)
  • Phenytoin (Dilantin)
  • Phenobarbital
  • Rifabutin
  • Rifapentine
  • Hypericum perforatum (St. John's wort)

• More than 1 week since prior and no other concurrent enzyme-inducing anticonvulsants, including any of the following:

  • Felbamate (Felbtol)
  • Primidone (Mysoline)
  • Oxcarbazepine (Trileptal)

• No concurrent chronic treatment with systemic steroids or another immunosuppressive agent

  • Concurrent physiologic or stress doses of steroids allowed in patients with endocrine deficiencies
• No other concurrent investigational therapy
• No other concurrent anticancer therapy, including chemotherapy, radiotherapy, immunotherapy, or biologic therapy
• No concurrent live vaccines