The Efficacy of High-Dose Chemotherapy Followed by Autologous Stem Cell Transplantation in Ewing Sarcoma Patients

<b>Background:</b> Ewing sarcoma (ES) is a highly aggressive malignant tumor that predominantly affects children and young adults. Despite advances in multimodal therapy, relapse and refractory disease remain the leading causes of treatment failure. High-dose chemotherapy followed by autologous stem cell transplantation (HDCT-ASCT) has been proposed as a consolidation strategy for high-risk or relapsed ES; however, its clinical value remains controversial. <b>Methods:</b> We retrospectively analyzed 46 consecutive patients with locally advanced or metastatic ES who underwent HDCT-ASCT after at least one prior systemic therapy line. Clinical, pathological, and transplant-related variables were evaluated for associations with overall survival (OS), post-transplant OS (OS-2), and progression-free survival (PFS). Survival was estimated using the Kaplan-Meier method, and prognostic factors were assessed by Cox proportional hazards modeling. <b>Results:</b> The median age at diagnosis was 23 years (range: 14-55). Median OS from diagnosis was 42 months, while post-transplant OS-2 and PFS were 8 and 5 months, respectively. Younger patients (≤23 years) had significantly longer OS (50 vs. 34 months; <i>p</i> = 0.027). Liver metastasis predicted inferior OS (HR = 5.411; <i>p</i> = 0.006), whereas lung metastasis was associated with shorter OS-2 (HR = 2.672; <i>p</i> = 0.025) and PFS (HR = 6.037; <i>p</i> = 0.016). Treatment-related mortality was low (2.1%), though hematologic toxicity was universal. Overall, HDCT-ASCT provided transient disease control, with modest benefit confined to younger, chemosensitive, and medically fit patients. <b>Conclusions:</b> In this real-world cohort, HDCT-ASCT was feasible and safe but offered limited survival advantage in heavily pretreated Ewing sarcoma. Prognosis was primarily influenced by age and metastatic distribution, particularly hepatic and pulmonary involvement. These findings support a risk-adapted, biology-driven approach reserving HDCT-ASCT for selected patients and highlight the need for post-transplant maintenance strategies integrating targeted or immunotherapeutic modalities.