3.2 | Ewing sarcoma
3.2.1 | Demographic, diagnosis, disease, and treatment variables
As shown in Table 1 , patients treated at a pediatric center were more likely to be younger and have limb involvement than those treated at an adult center. Clinical trial enrollment was significantly more frequent in pediatric centers versus adult centers (53% versus 2%, p<0.001). Sex, DIL, and socioeconomic status did not differ by LOC.
Pediatric centers provided their EWS patients with local therapy (either surgery only or radiation only or both surgery and radiation) earlier than adult centers, regardless of the type of local therapy (Table 3 ). Time to local therapy was not significantly different between localized and metastatic patients. There was no statistically significant difference in radiation doses between pediatric and adult centers.
The most commonly used chemotherapeutic agents were cyclophosphamide, doxorubicin, ifosfamide and etoposide. The median cumulative doses of cyclophosphamide, ifosfamide, etoposide, and the CED were significantly higher in pediatric center patients compared with adult center patients.
3.2.2 | Survival outcomes
The median follow-up time was 6.6 years (IQR 1.7 to 14.1 years; range 0.5-25.2 years). None of the variables (including locus of care/age and primary site) was associated with EFS in localized cohort (Fig. 2A and 2B ). In metastatic cohort, only receiving higher dose of etoposide was significantly associated with higher EFS rate (5-year EFS ± SE: 25% ± 11% vs 0; 0.0001).
Table 4 demonstrates the results of Cox proportional hazards survival analyses in both localized and metastatic EWS cohorts. In univariate analysis of the localized disease cohort, none of the variables including locus of care/age and primary tumor location showed statistically significant association with survival. In multivariable analysis, none of the variables was significantly associated with EFS (Table 4 ). In the metastatic cohort multivariable analysis, only the association of cumulative doses of etoposide showed statistically significant association with EFS (Table 4 ).