P1.036: Multicenter Evaluation of Prognostic Factors in Pediatric Ewing Sarcoma

Background: Ewing sarcoma (ES) is the one of the most common primary soft tissue sarcoma in the pediatric population. Treatment algorithms for ES is dependent on risk stratifying patients based on outcomes. Given this, the purpose of this study was to identify predictors of survival in three tertiary referral centers.

Methods: Patients treated for ES at three tertiary pediatric hospitals (Texas Children’s Hospital, Children’s National, and UT San Antonio) between 2010 and 2020 were utilized for retrospective analysis. Patient and tumor characteristics, treatment algorithms, and patient outcomes were evaluated from the electronic medical record. Events were defined as relapse or progression of disease. Outcomes were determined through overall survival (OS) at the 5 years from diagnosis.

Results: One hundred and twenty-six patients met inclusion criteria. Male patient had higher OS (78%) compared to female patients (63%, p=0.05). Tumors located in the extremity had the highest level of OS at 81% (p=0.008) while tumors located in the pelvis had the lowest OS at 35% (p < 0.0001) compared to all other locations. Obtaining an R0/R1 resection was associated with higher survival (82%) compared to those that had a R2 resection (44%, p=0.01). Patients that experienced an event had a lower OS (22%) compared to those that did not (94%, p< 0.0001). Patients that died were noted to have an average percent of gross viable tumor of 8.4% compared to those that survived that had 1.4% (p=0.008).

Conclusion: Patients that experienced an event, those presenting with ES in the pelvis, and those with R2 resection were associated with lower OS. Tumors with a higher average percent of gross viable tumor when resected were associated with death. Further studies evaluating risk stratifying patients based on these characteristics may improve outcomes for these patients.