4. Prior therapy: Patients with NF1 are eligible at the time of recurrence or progression of inoperable PN. A surgical consultation should be obtained prior to enrollment on the study to evaluate if tumor resection is a feasible option. Patients will only be eligible if complete tumor resection is not feasible or if a patient with a surgical option refuses surgery. Since there is no standard effective chemotherapy for patients with NF1 and progressive PN, patients may be treated on this trial without having received prior therapy. Patients must have recovered from the toxic effects of all prior therapy before entering this study. The Cancer Therapy Evaluation Program Common Toxicity Criteria (CTC) Version 2.0 will be used for toxicity assessment. Recovery is defined as a toxicity grade < 2, unless otherwise specified in the Inclusion and Exclusion Criteria. Patients must have had their last dose of radiation therapy at least 6 weeks prior to study entry, and their last dose of chemotherapy at least four weeks prior to study entry. Patients who received granulocyte-colony stimulating factor (G-CSF) after the prior cycle of chemotherapy must be off G-CSF for at least one week prior to entering this study.