Definitive irradiation in multidisciplinary management of localized Ewing sarcoma family of tumors in pediatric patients: Outcome and prognostic factors

Purpose To assess the effect of radiation dose on local tumor control of the Ewing sarcoma family of tumors in 79 patients with localized disease treated at a single institution. Methods and materials Thirty-seven patients received vincristine, actinomycin D, cyclophosphamide, and doxorubicin, and 42 received vincristine, actinomycin D, and cyclophosphamide, with alternating cycles of ifosfamide and etoposide; all underwent definitive radiotherapy (median dose, 37.5 Gy) with either low-dose (<40 Gy) or standard dose (≥40 Gy) radiation delivered according to the protocol. We calculated the cumulative incidence of local treatment failure, disease recurrence, and overall survival and analyzed the effect of known prognostic factors and radiation dose. Results The cumulative incidence of local treatment failure at 10 years was 30.4% and that of disease recurrence was 40%. The overall survival rate was 64.5%. Patient age ≥14 years and tumor size ≥8 cm were adverse prognostic factors for local treatment failure; patient age ≥14 years was also associated with worse survival. Although the radiation dose alone did not predict for local treatment failure, the cumulative incidence of local failure at 10 years was 19% when tumors <8 cm were treated with <40 Gy, and no patient treated with standard doses (≥40 Gy) developed local recurrence (p = 0.084). Conclusion Tumor size and patient age predict for local tumor control in patients with Ewing sarcoma family of tumors treated with systemic therapy and definitive radiotherapy. Patients treated with reduced-dose radiotherapy experienced unacceptably high rates of local recurrence.