A COMPARISON BETWEEN SPORADIC AND NF1-ASSOCIATED MALIGNANT PERIPHERAL NERVE SHEATH TUMOURS

Abstract

Malignant peripheral nerve sheath tumours (MPNSTs) constitute 10% of soft tissue sarcomas. A significant proportion arise in neurofibromatosis type 1 (NF1). Several publications have compared MPNST survival in sporadic and NF1 patients, without consensus on whether NF1 is an independent factor for poor prognosis.

Clinical and histological data from 135 proven MPNSTs were analysed from 2 national centres for soft tissue tumour surgery diagnosed from 1979 to 2000. 129 patients had follow-up data from 6 months to 21 years. 35 were from patients with NF1. Local treatment involved surgery in surgery in 95%, radiotherapy in 44% and chemotherapy in 21%.

NF1 patients were younger than those with sporadic tumours (median age 26 years vs 53 years, p< 0. 001). Overall MPNST survival was almost identical to that in soft tissue sarcomas as a whole, but was worse in NF1 than in sporadic tumours (33% vs 72% at 30 months [p< 0. 01], 17% vs 39% at 60 months, 6% vs 21% at 120 months). A trend towards shorter time to local recurrence was seen in NF1, but not time to metastasis. Superficial tumours gave improved prognosis. Tumour volume over 100ml was associated with worse survival (46% vs 91% at 30 months, p< 0. 02), as was histological grade (80% high grade vs 25% low grade at 60 months, p< 0. 01). In terms of location, a non-significant over-representation of NF1 MPNSTs in the sciatic and brachial plexii was identified.

NF1 and sporadic MPNSTs exhibited no difference in depth or tumour volume profile, although NF1 tended towards higher grade. Analysis of survival in only high grade tumours, however, still resulted in a significant survival disadvantage in NF1 (33% vs 70% at 30 months, p< 0. 01). Removal of brachial and sciatic plexus tumours from analysis did not affect survivorship profiles in NF1 and sporadic MPNSTs.

Grade, volume and tumour depth correlate with survival; only 7 of 45 patients with deep high grade tumours over 100ml volume were observed to survive beyond 2 years. MPNST survival is worse in NF1 than sporadic tumours. Grade, depth, site and volume differences could not explain this disadvantage.