Enrico Martin

27 Abstract Background Currently, literature is scarce on differences across all possible tumor sites in malignant peripheral nerve sheath tumors (MPNSTs). To determine differences in treatment and survival across tumor sites and assess possible predictors for survival, we used the Surveillance, Epidemiology, and End Results (SEER) database. Methods MPNST cases were obtained from the SEER database. Tumor sites were recoded into: intracranial, spinal, head and neck (H&N), limbs, core (thorax/abdomen/ pelvis), and unknown site of origin. Patient and tumor characteristics, treatment modalities, and survival were extracted. Overall survival (OS) was assessed using univariable and multivariable Cox-regression hazard models. Kaplan-Meier survival curves were constructed per tumor site for OS and disease-specific survival (DSS). Results 3267 MPNST patients were registered from 1973-2013; 167 intracranial (5.1%), 119 spinal (3.6%), 449 H&N (13.7%), 1022 limb (31.3%), 1307 core (40.0%), and 203 unknown (6.2%). The largest tumors were found in core sites (80.0mm, IQR: 60.0- 115.0mm) and the smallest were intracranial (37.4mm, IQR: 17.3-43.5mm). Intracranial tumors were least frequently resected (58.1%), whereas spinal tumors were most often resected (83.0%). Radiation was administered in 35.5-41.8%. Independent factors associated with decreased survival were: older age, male sex, black race, no surgery, partial resection, large tumor size, high tumor grade, H&N site, and core site (all p<0.05). Intracranial and pediatric tumors show superior survival (both p<0.05). Intracranial tumors show superior OS and DSS curves, whereas core tumors have the worst (p<0.001). Conclusion Superior survival is seen in intracranial and pediatric MPNSTs. Core and H&N tumors have a worse prognosis. 2