Peripheral nerve sheath tumor with metastases is rare. This term is preferred to older designations such as malignant schwannomas and neurofibrosarcomas. It is most common in the deep soft tissue, usually in close proximity of a nerve trunk. The most common sites include the sciatic nerve, brachial plexus, and sarcal plexus. The first-line treatmenet is surgical resection with wide margins. Chemotherapy (e.g. high-dose doxorubicin) and often radiotherapy are often done as adjuvant and/or neoadjuvant treatment but is supported solely by case reports. Other reproted chemo drugs include vincristine and cyclophophamide. I was not able to find any literature on the use of Nexavar.
Evans DG, Baser ME, McGaughran J, Sharif S, Howard E, Moran A. Malignant peripheral nerve sheath tumours in neurofibromatosis 1. J Med Genet 2002;39:311-4.