Observational Study in Localized Osteosarcoma

Inclusion Criteria: * Diagnosis of high grade OS of the extremities * Age at diagnosis ≤ 40 years at the time of diagnosis * Localized disease (skip metastases are allowed) * Adequate organ function according the AIEOP/ISG OS 2021 recommendation * Patients or parents oe guardians of minors who have given their written informed consent to participate in the study Exclusion Criteria: * Presence of metastases * Diagnosis of periosteal OS, of parosteal OS or secondary OS * Any medical condition which can not allowed the use of the treatments recommended by AIEOP/ISG OS 2021