Enrico Martin

75 Treatment and survival in pediatric MPNST Results Patient population From a total of 879 patients registered in the NCR database, 784 had the final diagnosis of MPNST. Of this group 70 patients were children (8.9%, Table 1 ). Demographically there were no statistically significant differences between presentation of adult and pediatric MPNSTs (all p>0.05). There was a trend for a higher incidence of NF1 in pediatric patients (37.1% vs. 25.8%, p = 0.06). In pediatric patients there was a slight male predilection (54.3%). Tumors were usually large (>5cm, 71.4%) and most commonly located in truncal sites (45.7%); three of which had a retroperitoneal MPNST (4.3%). Tumors tended to be larger in NF1 patients compared to non-NF1 pediatric patients, 92.3% and 59.1% respectively (p = 0.05, Table 2 ). Tumor site, tumor depth, and presence of rhabdomyoblastic differentiation did not differ significantly between pediatric NF1 and non-NF1 patients (all p>0.05). A total of six children (8.6%) initially presented with metastatic disease, of which all were in non-NF1 patients. Table 2 Clinicopathologic differences between NF1 and non-NF1 pediatric patients. Variable Pediatric Non-NF1 NF1 P Number of patients 70 44 26 Male gender 38 (54.3%) 27 (61.4%) 11 (42.3%) 0.19 Site Extremities 24 (34.3%) 15 (34.1%) 9 (34.6%) 0.65 Trunk 29 (41.4%) 16 (36.4%) 13 (50.0%) Retroperitoneum 3 (4.3%) 2 (4.5%) 1 (3.8%) Head & Neck 11 (15.7%) 9 (20.5%) 2 (7.7%) NOS 3 (4.3%) 2 (4.5%) 1 (3.8%) Tumor size ≤5cm 10 (28.6%) 9 (40.9%) 1 (7.7%) 0.05 >5cm 25 (71.4%) 13 (59.1%) 12 (92.3%) NA 35 22 13 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 3 (4.3%) 1 (2.3%) 2 (7.7%) 0.55 Synchronous metastasis 6 (8.6%) 6 (13.6%) 0 (0.0%) 0.08 Time period 1989-2005 43 (61.4%) 26 (59.1%) 17 (65.4%) 0.62 2006-2017 27 (38.6%) 18 (40.9%) 9 (34.6%) cm: centimeters, NA: not available, NF1: neurofibromatosis type 1, NOS: not otherwise specified 4