Inclusion Criteria:  Diagnosis of Ewing's sarcoma of the bone Diagnosis of Ewing-like sarcoma (round cell sarcoma with fusion of the EWSR1 gene with others not of the ETS family, sarcoma with CIC rearrangement or sarcoma with BCOR rearrangement) Diagnosis of extraosseous Ewing's sarcoma for patients Age at diagnosis <50 years Assessment of the extent of the disease at onset in accordance with the European Society of Medical Oncology guidelines Patients or parents oe guardians of minors who have given their written informed consent to participate in the study  Exclusion Criteria:  1. Presence of comorbid factors who can compromise the compliance of the treatment plan or the evaluation of the outcomes, including but not limited to organ pathologies that contraindicate the use of chemotherapy and psychological or social conditions that do not allow for adequate compliance treatment or adequate follow-up