Lack of efficacy of neoadjuvant chemotherapy in adult patients with maxillo-facial high-grade osteosarcomas: A French experience in two reference centers.

•MFOS is a rare disease.•Tumor size and R0 surgical resection were significantly associated with DFS.•The clinical, pathological and radiological responses to neo-Ct were 5%, 0% and 5%.•For MFOS, there is lack of benefit and potentially deleterious effects of neo-CT.•We suggest privileging primary surgery followed by adjuvant chemotherapy for MFOS.