Proton Radiation in Children with Thoracic Ewing Sarcoma: Results of the Prospective KiProReg Registry

Abstract

Objectives

Proton therapy (PT) is increasingly used for the treatment of thoracic Ewing sarcoma (EwS), aiming to reduce radiotherapy-related side effects. We examined pediatric patients with thoracic EwS treated with PT.

Methods

Children with localized thoracic EwS participating in the internal KiProReg registry treated at our institution between 2014 and 2023 were included. Data on patients, tumor, treatment and side effects (acc. to CTCAEv4/5) was analyzed.

Results

Twenty-eight children (14m, 14f) with a median age of 11.4 years (range 1.9-17.1) were included. Twenty-seven children received chemotherapy before and 16 concomitant to PT. Treatment concepts were adjuvant/definitive/neoadjuvant in 68%/21%/11%, respectively. Complete resection was achieved in 14 children. All children were treated locally on the primary tumor or local recurrence. Median total dose was 50.4 Gy (range 45.0-59.4 Gy). Median follow-up time after initial diagnosis was 37.5 months (range 6.6-113.3 months). Local tumor control was achieved in 25 patients (89.3%), three patients developed dissemination. In total, three patients deceased. Early higher-grade (>grade2) side-effects during PT occurred in 19 patients, predominantly on skin (n=5) and/or blood/lymphatic system (n=16). One patient developed a late fracture in the irradiated area. Among patients with ≥ 1 year FU after PT (n=20), no high-grade late cardiac/pulmonary toxicities have been observed to date.

Conclusion

PT was well tolerated in this challenging sample. Local control was achieved in the majority of patients. These results need to be confirmed with longer follow-up and in larger cohorts.