# Favourable outcomes of extraskeletal Ewing sarcoma treated on a non-dense chemotherapy backbone with inclusion of radiotherapy for local control

## TL;DR

Children with extraskeletal Ewing sarcoma treated with non-dense chemotherapy and radiotherapy had favorable survival rates, especially when local therapy was timely.

## Contribution

The study demonstrates favorable outcomes using non-dense chemotherapy and radiotherapy for Ewing sarcoma in children.

## Key findings

- Four-year overall survival in localized cases reached 88.6%, comparable to Western cohorts.
- Timely local therapy delivery significantly improved event-free and overall survival.
- Low albumin levels and delayed local therapy were negative prognostic factors.

## Abstract

Extra skeletal Ewing sarcoma (EES) has less clearly defined clinical behaviour and treatment strategies. We report the clinical profile, outcomes and prognostic factors of children with EES treated at a single centre over a decade on a non-dose chemotherapy backbone.

Children ≤15 years of age with EES treated from January 2012 to December 2021 were retrospectively analysed. All received EFT-2001, a non-dose chemotherapy protocol. Local therapy was planned after 9–12 weeks of chemotherapy.

One hundred and six patients formed the study cohort. The majority of the primary was axial in location. Metastasis was present in 25.5%, mainly in the lungs. Local therapy was definitive radiotherapy in 59.1% (n = 58), surgery only in 3% (n = 3) and surgery and radiotherapy in 37.9% (n = 37). At a median follow-up of 43 months (range, 33–52 months), 4-year event-free survival (EFS) and overall survival (OS) of the whole cohort were 70.4% (95% CI: 60.8%–85.3%) and 86.5% (95% CI: 79.3%–94.1%). Four-year EFS and OS of the localised cohort were 73.8% (95% CI: 60%–83.3%) and 88.6% (95% CI: 87.4%–90.2%) and those of the metastatic cohort were 32.4% (95% CI: 21.4%–86.5%) and 61.9% (95% CI: 54.1%–86.3%), respectively. On multivariate analysis, EFS was affected by albumin ≤ 3 g/dL (p = 0.01) and delay in any type of local therapy from initiation of chemotherapy ≥12 weeks (p = 0.01), whereas OS was affected by male gender (p = 0.02).

Survival of children with EES treated on a strategy based on non-dose dense chemotherapy with inclusion of radiotherapy as local control modality is comparable to the Western cohorts, especially in the localised setting. Timely delivery of local therapy is imperative for optimal outcomes.