Treatment differences and long-term outcomes in adults and children with Ewing sarcoma

Ewing sarcoma is an aggressive malignancy primarily affecting children and adolescents. Limited research is available on treatment practices, clinical course, and survival in adults.

A multi-institution retrospective cohort study of all adults (>18 years) and children (≤18 years) with Ewing sarcoma treated in British Columbia, Canada between January 01, 2000 and December 31, 2018.

One-hundred seven individuals (66 adults, 41 children) were included in the analysis. 5-year OS was 58 % in adults and 75 % in children. For individuals with local disease, 5-year OS was 74 % in adults and 84 % in children. Adult status was associated with impaired PFS (HR, 1.8; 95 % CI, 1.0 - 3.1, p=0.04) and OS (HR, 1.8; 95 % CI, 0.9 - 3.5; p=0.088). A Charlson Comorbidity Index (CCI) ≥3 was associated with impaired survival in adults and children (HR, 3.9, 95 % CI, 2.0 - 7.5; p=<0.001); baseline CCIs were not significantly different between groups. Most adults (61/66; 92 %) and all children (41/41; 100 %) received systemic treatment with no significant difference in mean lines of therapy, treatment modalities or agents. Most children received interval-compressed chemotherapy (35/41; 85 %) compared to adults (19/61; 29 %; p=<0.001). Interval-compression was not significantly associated with improved survival in adults with local disease (HR, 0.51; 95 % CI 0.1 - 2.3; p=0.373). Children more often initiated treatment within 28 days of diagnosis (31/33; 94 %) compared to adults (41/64; 64 %, p=0.001). Treatment within 28 days was associated with improved survival in the entire cohort (HR, 2.04 95 % CI, 1.1 - 3.9; p = 0.03). This association was preserved in subanalysis of individuals with local disease (HR, 5.4; 95 % CI, 1.9 - 15; p = 0.001) and only adults (HR, 5.3, 95 % CI, 1.7 - 17; p = 0.005).

Survival for adults with Ewing sarcoma is inferior to children despite similarities in presentation, tumour characteristics and treatments. Further studies on the value of interval-compression in adults are required. Timely initation of treatment should be a priority for this disease.