Bosma SE, Rueten-Budde AJ, Lancia C, et al. - In a large cohort of patients with Ewing sarcoma treated according to the EURO–E.W.I.N.G 99 protocol (EUROpean Ewing tumor Working Initiative of National Groups–Ewing Tumor Studies), researchers examined the impacts of surgical margins, histological response, and radiotherapy on local recurrence (LR), distant metastasis (DM), and survival in Ewing sarcoma. The study sample consisted of 982 patients. Using Cox proportional hazard models, effect of risk factors was estimated. According to findings, risk factors for progression to DM or death are disease extent and histological response. Risk factors for LR are tumor site and surgical margins. Prior risk factors lose their relevance if disease progression occurs. Time to recurrence is important for decision-making in case of isolated LR. Especially in pelvic/axial, radiotherapy appears to be protective for LR. The need for radiotherapy in extremity Ewing sarcoma is questioned due to low percentages of LR in extremity tumors and related toxicity.