Oncologic outcomes of sporadic, neurofibromatosis-associated, and radiation-induced malignant peripheral nerve sheath tumors.

BACKGROUND: Malignant peripheral nerve sheath tumors (MPNSTs) occur sporadically, after prior radiation therapy (RT), or in association with neurofibromatosis type 1 (NF1). It is controversial whether patients with NF1-associated MPNST have worse outcomes. We investigated the prognostic significance of sporadic, NF1-associated, and RT-induced MPNST.

METHODS: Patients with primary high-grade MPNST from 1982 to 2011 were identified from a prospectively maintained database. Patients with sporadic MPNST were included only if the MPNST was not associated with NF1 or a neurofibroma or if it was immunohistochemically S100-positive.

RESULTS: We studied 105 patients; 42 had NF1-associated tumors, 49 sporadic, and 14 RT-induced. Median age at diagnosis was 38 years. Median follow-up for surviving patients was 4 years. Mean tumor diameter was 5.5 cm for RT-induced tumors and 9.7 cm for NF1-associated and sporadic tumors (P=0.004). In multivariate analysis, factors associated with worse disease-specific survival (DSS) were larger size (HR 1.08; 95% CI 1.04-1.13; P<0.001) and positive margin (HR 3.30; 95% CI 1.74-6.28; P<0.001). Age, gender, site of disease, and S100 staining were not associated with DSS. The 3-year and median DSS were similar for NF1 and sporadic cases; combined 3-year DSS was 64% and median DSS was 8.0 years. For RT-induced tumors, 3-year DSS was 49% and median DSS was 2.4 years. The relationship between RT association and DSS approached statistical significance (HR 2.29; 95% CI 0.93-5.67; P=0.072).

CONCLUSIONS: Margin status and size remain the most important predictors of DSS in patients with MPNST. NF1-associated and sporadic MPNSTs may be associated with improved DSS compared with RT-induced tumors.