I. Epidemiological characteristics The incidence of bone tumors in the population is about 0.01%. Among them, the incidence of osteosarcoma is 2-3 per million people per year. The mortality rate of bone and joint malignant tumors accounts for 1.6% of all malignant tumors. Over the years, because of the low incidence rate, it is difficult for many doctors to accumulate sufficient experience. Before 1972, the only treatment was amputation, and the survival rate was only 19.7%. In 1972, adjuvant chemotherapy was proposed by Norman Jaffe, and in 1975, Rosen proposed neoadjuvant chemotherapy, and the limb preservation rate was significantly improved. In China, chemotherapy for osteosarcoma was first introduced in 1979 at the Beijing Jishuitan Hospital, and the ISOLS International Society for Limb Preservation was established in 1983 and the CSCO Osteosarcoma Expert Committee was established in 2009. The standard treatment pathway for osteosarcoma mainly includes: clear diagnosis, neoadjuvant chemotherapy, grasp of contraindications for limb preservation, standardized surgical resection with extensive borders, postoperative chemotherapy, and close follow-up. After years of international research and clinical practice work, the standardized treatment pathway for osteosarcoma is now mature. The most common metastases of osteosarcoma are pulmonary and intraosseous metastases, and inappropriate treatment can bring catastrophic outcomes, with loss of life for those who can be saved and loss of limbs for those who can be preserved. With standardized treatment, about 60% of patients can achieve clinical cure and 90% of patients can retain their limbs, so a standardized treatment team is needed for medical treatment. The treatment steps are as follows: Prior to treatment, various tests should be completed, including: lung CT, bone scan, local CT with enhancement and MRI with enhancement.