5 CONCLUSIONS
Histological necrosis post neoadjuvant chemotherapy is prognostic of outcomes on a non-HDMTX based chemotherapy backbone in children with osteosarcoma. Tumor necrosis at a cut-off of 90% in localized disease is a good prognostic tool on a non-HDMTX based chemotherapy backbone, though best outcomes are seen with 100% TN, but 70% TN and other lower cut-offs require further exploration for survival predictive value. A lower cut-off of 70% (or other) in metastatic disease could be used for prognostication, which needs validation in a larger cohort. Amputation and male gender predict poor histological necrosis, probably driven by bad biology.