A synopsis model of osteosarcoma: Questions to be answered and future challenges. MTX, methotrexate; DDP, cisplatin; ADM, adriamycin; IFO, ifosfamide; L-MTP-PE, liposomal muramyl tripeptide phosphatidyl ethanolamine; TXT, docetaxel; GEM, gemcitabine; HD, high-dose.