Observational Study in Localized Osteosarcoma

Who May Qualify: - Diagnosis of high grade OS of the extremities - Age at diagnosis ≤ 40 years at the time of diagnosis - Localized disease (skip metastases are allowed) - your organs (liver, kidneys, etc.) are working well enough based on blood tests according the AIEOP/ISG OS 2021 recommendation - Patients or parents oe guardians of minors who have given their written willing to sign a consent form to participate in the study Who Should NOT Join This Trial: - 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 Always talk to your doctor about whether this trial is right for you.