Enrico Martin

74 Chapter 4 method to compare adult and pediatric MPNSTs, metastatic and non-metastatic pediatric MPNST, and in localized pediatric patients for NF1 status, tumor depth, tumor size, resection margin, and time period of diagnosis. Kaplan-Meier curves were made for all comparisons of localized pediatric patients only, except for the comparison of metastatic versus localized disease at presentation. Differences were assessed using the log-rank test. A multivariate Cox proportional hazard model was constructed by backward selection for localized pediatric MPNSTs only. P-values <0.05 were considered statistically significant. In order to create a parsimonious model, a ratio of five events per degree of freedom was chosen. Additionally, adjusted survival curves were constructed for individual prognostic factors based on the final model. 23 Statistical analyses and data visualization were conducted using R version 3.6.0 (R Core Team, 2019). Table 1 Clinicopathologic differences between adult and pediatric patients Variable Overall Pediatric Adult P Number of patients 784 70 714 Male gender 421 (53.7%) 38 (54.3%) 383 (53.6%) 1.00 NF1 210 (26.8%) 26 (37.1%) 184 (25.8%) 0.06 Site Extremities 303 (38.6%) 24 (34.3%) 279 (39.1%) 0.78 Trunk 312 (39.8%) 29 (41.4%) 282 (39.5%) Retroperitoneum 43 (5.5%) 3 (4.3%) 40 (5.6%) Head & Neck 100 (12.8%) 11 (15.7%) 89 (12.5%) NOS 26 (3.3%) 3 (4.3%) 24 (3.4%) Tumor size ≤5cm 190 (32.1%) 10 (28.6%) 180 (32.3%) 0.65 >5cm 402 (67.9%) 25 (71.4%) 377 (67.7%) NA 192 35 157 Tumor depth Superficial 6 (14.0%) 3 (12.0%) 3 (16.7%) 0.68 Deep 37 (86.0%) 22 (88.0%) 15 (83.3%) NA 27 19 8 Triton tumor 48 (6.1%) 3 (4.3%) 45 (6.3%) 0.68 Synchronous metastasis 90 (11.5%) 6 (8.6%) 84 (11.8%) 0.56 Time period 1989-2005 454 (57.9%) 43 (61.4%) 411 (57.6%) 0.62 2006-2017 330 (42.1%) 27 (38.6%) 303 (42.4%) cm: centimeters, MPNST: malignant peripheral nerve sheath tumor, NA: not available, NF1: neurofibromatosis type 1, NOS: not otherwise specified