Risk factors in pediatric Malignant Peripheral Nerve Sheath Tumors (MPNST): Results from the French Pediatric Oncology Society (SFCE) cohort

Introduction: Malignant Peripheral Nerve Sheath Tumors (MPNST) are very rare and aggressive tumors, which can affect children, adolescents, and young adults. These tumors are frequently associated with type 1 neurofibromatosis (NF1). This study aims to determine prognostic factors in unselected pediatric MPNST to specify the risk stratification strategy. Methods: A national multicenter retrospective study encompassing all French pediatric patients (0–18 years) treated for MPNST, confirmed by a pathology review, from 1995 to 2017. Results: Overall, 66 patients (median age 13.0 years [range, 0.1–18.0]) developed a MPNST located in the limbs (36%), trunk (27%), head and neck (21%) and para-vertebral area (15%). Forty-eight percent of patients had NF1, 50% had a histologic grade III tumor and 77% a large tumor (>5 cm), including 30% very large (>10 cm). Most patients (94%) had localized tumors. After a median follow-up of 7.6 years [range, 0.4–18.7], the 5-year overall (OS) and event-free (EFS) survivals were 46.7% [95%CI, 35.8–60.8] and 40.8% [95%CI, 30.3–54.9], respectively. On multivariate analysis were found to be associated with a worse outcome (OS): metastatic disease (HR (Hazard-Ratio) 6.4 [1.8; 22.0]), grade 3 FNCLCC (HR 4.77 [1.4; 15.8]),> 10-cm size (HR 2.3 [1.1; 4.8]) and the presence of NF1 (HR 2.2 [1.1; 4.4]). Histologic subtypes of MPNST (classical, malignant Triton or epithelioid tumor) were not correlated with outcome. Conclusion: The overall outcome of MPNST was poor in patients with NF1 and in high grade, very large and metastatic tumors. The identification of these risk factors allows us to define adapted risk stratification to propose new therapeutic strategies for high-risk cases.