PEG-Interferon Alfa-2b in Treating Young Patients With Plexiform Neurofibroma

DISEASE CHARACTERISTICS: * Diagnosis of plexiform neurofibroma which is progressive, symptomatic, or life threatening and for which there is no other standard medical management or surgical option * Histologic confirmation of tumor is not required in the presence of consistent clinical and radiographic findings provided the following are true: * No clinical observation or scan suggestive of malignant transformation * Meets ≥ 1 of the following diagnostic criteria for neurofibroma type 1 (NF1): * Six or more cafe-au-lait spots (\> 0.5 cm in prepubertal patients or \> 1.5 cm in post pubertal patients) * Freckling in axilla or groin * Optic glioma * Two or more Lisch nodules * A distinctive bony lesion (e.g., dysplasia of the sphenoid bone, dysplasia, or thinning of long bone cortex) * A first degree relative with NF1 * No history of malignant peripheral nerve sheath tumor * No active visual pathway glioma * No active brain tumor or brain metastases PATIENT CHARACTERISTICS: Performance status * ECOG 0-2 Life expectancy * At least 12 months Hematopoietic * Absolute neutrophil count \> 1,500/mm\^3 * Hemoglobin \> 10 g/dL * Platelet count \> 100,000/mm\^3 Hepatic * Bilirubin \< 1.5 mg/dL * SGPT ≤ 2 times upper limit of normal * No significant hepatic dysfunction Renal * Creatinine based on age as follows: * ≤ 0.8 mg/dL (for patients age 5 years and under) * ≤ 1.0 mg/dL (for patients age 6 to 10 years) * ≤ 1.2 mg/dL (for patients age 11 to 15 years) * ≤ 1.5 mg/dL (for patients age 16 to 21 years) OR * Creatinine clearance ≥ 70 mL/min Cardiovascular * No significant cardiac dysfunction * No severe cardiovascular disease * No cardiac arrhythmia requiring chronic treatment * No congestive heart failure * No symptomatic ischemic heart disease Pulmonary * No significant pulmonary dysfunction Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No serious infection * No other significant unrelated systemic illness * No significant organ dysfunction * No other malignancy except surgically cured nonmelanoma skin cancer or carcinoma in situ of the cervix * No history of severe psychiatric condition or psychiatric disorder requiring hospitalization * No history of suicidal ideation or attempt * No thyroid dysfunction unresponsive to therapy * No uncontrolled diabetes mellitus * No history of HIV positivity * No alcohol or drug abuse PRIOR CONCURRENT THERAPY: Biologic therapy * No concurrent immunotherapy * No concurrent colony-stimulating factors (e.g., erythropoietin or filgrastim \[G-CSF\]) Chemotherapy * No concurrent chemotherapy for this disease Endocrine therapy * No concurrent chronic systemic corticosteroids * No concurrent hormonal therapy for this disease Radiotherapy * No concurrent radiotherapy for this disease Surgery * Prior surgery allowed provided it has been at least 21 days since surgery and there is presence of residual tumor Other * Recovered from prior therapy * More than 30 days since prior investigational agents