Disparate Outcomes, Biologic and Therapeutic Differences in Pediatric versus Adult Patients with Ewing Sarcoma

Ewing sarcoma (ES) is a small blue round cell sarcoma affecting a wide age spectrum. Clinical advances predominately stem from pediatric research consortia clinical trials. In most series, adults have poorer outcomes when compared to children. The aim of this study was to perform a detailed evaluation of factors potentially accounting for this difference.

A single institution retrospective chart review was conducted on patients with ES diagnosed from 2005 to 2015, identified using a free-text search engine with the keywords "Ewing sarcoma" as well as a corresponding pathologic database. Data were analyzed based on age, pediatric (age <18) and adult (age >18 years), using a multivariate analysis model.

Eighty-eight ES patients (34 pediatric, 54 adult) were identified with a median age of 13 (range 3-18) and 31 (range 19-70) in their respective cohorts. Five-year overall survival (OS) was higher in pediatric patients (73.5% vs. 48.1%, p = 0.0213). By stage, 5-year OS in pediatric versus adult patients was 65% versus 20% (p = 0.0530) in metastatic (n = 32) and 68.1% versus 58.8% (p = 0.278) in localized (n = 56) patients. Lung-only metastases were present in 83% of metastatic pediatric patients versus 35% of adult metastatic patients. Pediatric patients received more cycles of first-line chemotherapy (13.8 vs. 11.4, p = 0.001), independent of stage. More cycles of chemotherapy correlated with improved OS (HR: 0.864, CI: 0.773-0.967) and progression-free survival (HR: 0.897, CI: 0.808-0.996).

Outcome differences were most notable in patients with metastatic disease, although not statistically significant. Our series found differences in presentation between pediatric and adult populations with adult patients receiving fewer cycles of chemotherapy. This may suggest that both variations in underlying disease biology and potentially differences in treatment may account for outcome disparities.