[Recurrent or refractory Osteosarcoma and Ewing sarcoma-French guidelines from the FSG/NETSARC and GroupOs groups].

Osteosarcoma (OS) and Ewing Sarcoma (ES) are the two most frequent malignant bone tumors in children, adolescents and young adults. In case of disease recurrence, both are characterized by an aggressive behaviour and a relatively poor overall survival rate, with approximately a third of patients having a long-term disease-free survival. In case of recurrent or refractory (R/R) disease, the therapeutic strategy should be discussed in multidisciplinary staff meetings with expertise in bone sarcoma management. The standard management of R/R OS depends on the disease-free interval and the number and sites of metastases and is primarily surgical in patients with isolated lung metastases or local relapse. On the other hand, conventional chemotherapy remains the standard for R/R ES and include high-dose ifosfamide, cyclophosphamide with topotecan and irinotecan with temozolomide.