Enrico Martin

28 Chapter 2 Introduction Malignant peripheral nerve sheath tumors (MPNST) are rare sarcomas, encompassing only 2%-4% of all soft tissue sarcomas. 1,2 The incidence of these tumors is 1:100.000 in the general population. 3 However, in patients with neurofibromatosis type 1 (NF1) the incidence may be as high as 3-13% 4–6 and 23 to 51% of all MPNSTs are related to NF1. 4,7–12 A slight predominance in males has been reported. 7,9,10,13 The peak incidence of these tumors differs between NF1-related tumors and sporadic tumors. NF1 patients have an incidence peak in the third and fourth decades, sporadic tumors are usually diagnosed in the sixth decade. 12 Although some suggest a worse prognosis for NF1 patients, its influence on survival has recently been subject of debate. 9–12,14,15 Currently, no standardized treatment for MPNSTs exists. 3,10,16 Gross total removal of the tumor with wide margins is still considered the best prognostic factor for overall survival, which is reflected in the European Society for Medical Oncology Guidelines. 17 The ability for complete resection largely depends on the location of the tumor and its adjacent structures. 4,18–22 The efficacy and indications of radiotherapy remain to be a subject of debate. 23 Additionally, the role of chemotherapy in the treatment of MPNSTs is currently still under investigation, 24 with recent evidence indicating an added value of neoadjuvant epirubicin and ifosfamide in high grade, large, and deep MPNSTs. 25 Differences in survival per tumor site have repeatedly been reported. 10,11,14,26 However, variation in outcomes has not been assessed across all anatomical sites, mainly due to the rare nature of MPNSTs. The Surveillance, Epidemiology, and End Results (SEER) program is a cancer registry that collects data from 18 geographic areas across the United States, encompassing approximately 28% of its population. As such, the SEER database provides a means of assessing possible predictive factors of survival and treatment strategies for rare tumors as MPNSTs at different anatomical sites. This study appraises the differences in patient characteristics, treatment, and survival for MPNSTs arising from different sites in the SEER database. Methods Data Source Data were obtained from the SEER database from 1973-2013. The International Classification of Disease for Oncology (ICD-O-3) histology codes were used to identify cases. Malignant peripheral nerve sheath tumors (ICD-O-3: 9540/3, 9560/3, 9561/3) from any site were selected. Our Institutional Review Board has exempted the SEER program from review.