Adjuvant Radiotherapy for the Multimodal Treatment of Pediatric Ewing Sarcoma

Abstract

Purpose: This study aimed to report the adjuvant radiotherapy results of pediatric patients with Ewing sarcoma who received multimodal treatment for this rare disease using modern radiotherapy (RT) techniques. Materials and Methods: Pediatric patients with Ewing Sarcoma (ES) who received adjuvant radiotherapy were evaluated retrospectively. The study's primary endpoint was Overall Survival (OS) and disease-free survival (DFS). The secondary endpoint was local relapse-free survival after RT (LRFS- RT) and overall survival after RT (OS-RT). Results: The results of 18 pediatric patients diagnosed with Ewing Sarcoma in our clinic between 09.12.2013- 04.04.2021 and underwent RT for adjuvant were evaluated retrospectively. The three patients were excluded since they did not meet the inclusion criteria. The median age of the patients at the time of diagnosis was 10.5 (range 3-17). All the patients received pre-RT chemotherapy according to EURO-EWING 99. All the patients were operated and 7 (46.7 %) patients were R0; 4 (26.7%) patients were R1, and 4 (26.7%) patients were R2. RT was administered to patients for adjuvant purposes. The time from diagnosis to the onset of RT was 8.6 (range 2-20) months. The median fraction dose was 180 cGy, and the median total RT dose was 50.4 (range 45-55.80) Gy. The three patients (20%) received less than a total of 50 Gy, and 12 (80%) patients received a total of 50 Gy or more. The median follow-up period of the study was 27 (range 11-86) months. The 12 (80%) patients survived, and 3 (20%) died. The median OS diagnosis of the patients was 27.3 (range 11 to 86.5) months. The overall survival of the patients after RT was median 17.3 (range 4.4-83.9) months. Recurrence (local + distant) was observed in 7 patients (46.7%); 2 (13.3%) local, 3 (20 %) distant and 2 (13.3%) both. The median DFS was 24 months (range 1-86.5). Median LRFS-RT is 14.2 (range 1-83.9). The relationship between LRFS-RT and age (< 10 vs. over ≥ years old) (p0.050; HR:2.30; %95 CI 0.70-3.17) was significant. Significantly higher LRFS-RT was observed in the older age. No significant relationship was found between OS diagnosis, OSRT, and DFS and the following variables: gender (female vs. male), age at diagnosis (< 10 vs. over ≥ years old), tumor size (