(P 298) EWING SARCOMA OF MAXILLOFACIAL REGION AND SKULL: A RETROSPECTIVE MONOINSTITUTIONAL PEDIATRIC SERIES

Objective: Ewing sarcoma (ES) is one of the most common paediatric bone tumours. Skull and maxillofacial localization accounts approximately 3% of all cases and often local treatments are challenging, especially in younger children.

Methods: A chart review was conducted to identify children and adolescents with a diagnosis of maxillofacial/skull region ES treated from 2000 to 2022 at our Institution.

Results: Ten patients (7%) with a maxillofacial/skull localization were identified in our series of 131 ES patients diagnosed at our hospital. Median age at diagnosis was 10 years (range 3-18 years). Sites were: 6 paranasal sinuses, (of whom 1 originating from sphenoid sinus, 5 originating from maxillary sinus), 2 jaw, and 2 skull. Three out of 10 patients had metastatic disease at diagnosis (in one case lungs, in two cases lungs plus distant bones). All cases had EWSR1 fusions at molecular evaluation.
Patients received front-line chemotherapy (CT) according to on-going protocol.
Local treatment was performed with radiotherapy (RT) alone in 4 patients, RT and surgery in 4 patients, surgery alone in 2 patients.
Surgery was feasible in 6/10 patients, in 5 cases it was postponed after high-dose CT with BuMel, while one patient received radical surgery at diagnosis. Necrosis was assessed in all 5 cases, and in 4 was higher than 90%. All resections achieved wide margins. Reconstruction with autologous bone graft or free-flap fibula was used in 3 and 2 cases, respectively. Reconstruction failure occurred only in one case, requiring a second autologous bone graft.
The events reported were: 1 local recurrence at 24 months and 3 distant relapses at 8, 29 and 44 months, in all three patients metastatic at onset.
The median EFS was 26 months (range 8-44), median OS was 60 months (range 12-150).
Currently six patients are in first complete remission (CR), two patients deceased for progressive disease, one patient is alive in metastatic recurrence and one patient is lost to follow-up in CR at 18 months since diagnosis.

Conclusion: Although this is a small sample size, our report confirms that multimodal treatment with surgery and/or adjuvant RT allows a better outcome in pediatric patients with maxillofacial/skull ES.
Prognosis is largely depending on CT response and metastatic disease, as in fact all three patients with metastatic disease at diagnosis experienced a distant relapses. International collaborative efforts are needed to increase our knowledge in this extremely rare ES localization.