Study of Effectiveness of GEMDOX in Relapsed Osteosarcoma

Inclusion Criteria: * Age at diagnosis of high grade osteosarcoma \>= 4 * Received first line treatment with HD IFO * Following HD IFO treatment, they have been diagnosed refractory disease and they satisfy at least one of the following criteria : 1. Relapsed in the first 24 month following the initial diagnosis, regardless of location and resectability 2. Lung relapsed disease with more than 2 nodules diagnosed over 24 months from the initial diagnosis 3. Non resectable relapsed disease diagnosed over 24 months from the initial diagnosis Before or during GEMDOX treatment, eligible patients may have been subject to metastasectomy Exclusion Criteria: none