Session Item

To investigate outcome and toxicity of patients (pts) affected by malignant peripheral nerve sheath tumors (MPNSTs) treated with high-dose carbon ion radiotherapy (CIRT).

We retrospectively analyzed the outcome of 21 patients with MPNST treated between July 2013 and December 2020. Nineteen pts (90.5 %) were treated with post-operative RT. Residual disease was macroscopic in 11 pts (52 %), 8 pts (40.9 %) were treated for local recurrence after surgery. Two unresectable pts underwent definitive radiotherapy after biopsy. The most frequent tumor site was brachial plexus. The patients were irradiated with a median total dose of 63.9 Gy(RBE) (range, 54-76.8). Primary endpoints were overall survival (OS), local control (LC) and progression-free survival (PFS), calculated with Kaplan Meyer method. Secondary endpoint was toxicity, assessed according to Common Terminology Criteria for Adverse Events (CTCAE) version 5.0.  

Median follow-up was 25 months (range, 2 – 88). Three patients were lost to follow-up after median time of 27 moths (range, 16-41). Twelve local progressions (57%) were observed with a median time to local recurrence of 11 months (range, 1 – 66 months). Two distant metastases (9,5%) were recorded. OS at 2 and 3 years was 72% and 43%, respectively. LC at 2 and 3 years was 48% and 34%, respectively. PFS at 2 and 3 years was 48% and 34%, respectively. Acute toxicities of grade 2 (erythema and paresthesia) and grade 3 (erythema) in 4 patients were observed. Severe late radiation related toxicity of grade 3 (peripheral motor neuropathy and brachial plexopathy) was recorded in 2 patients.   

High dose CIRT shows favorable results with acceptable toxicities in patients with gross residual and local recurrence after surgery, or unresectable malignant peripheral nerve sheath tumors. Patients accrual by multidisciplinary approach is still ongoing to confirm these findings and investigate on this challenging disease.