I. Concept Adjuvant chemotherapy was first started in the 1960s, mostly in the postoperative period. Neoadjuvant chemotherapy started in 1973. At that time, artificial prostheses took a long time to fabricate (up to three months), and Drs. Rosen and Marcove at Memorial Sloan-Kettering Oncology Center administered preoperative chemotherapy to selected patients with osteosarcoma who were candidates for large tumor resection and artificial prosthesis replacement surgery to prevent continued tumor progression while waiting for the artificial joint to be fabricated. In 1979, Rosen et al. formally introduced the concept of neoadjuvant chemotherapy, in which he emphasized that neoadjuvant chemotherapy is not a simple model of “preoperative chemotherapy + surgery + postoperative chemotherapy”, but includes a comprehensive assessment of the patient and the tumor after preoperative chemotherapy. It involves a comprehensive assessment of the patient and the tumor after preoperative chemotherapy: the reduction of pain, the degree of mass reduction, and whether the lesion borders become clear on imaging, whether there is an increase in osteosclerosis, and whether there is a decrease in neovascularization of the tumor. Nowadays, the concept of neoadjuvant chemotherapy has been widely recognized. On the basis of postoperative adjuvant chemotherapy, most new chemotherapy regimens with the addition of preoperative chemotherapy have become the standard mode of treatment for malignant bone tumors. II. Role 1. Systemic treatment can be carried out early to eliminate potential micro metastases:Take osteosarcoma as an example, when the diagnosis is made clinically, 80% of these patients have already developed lung metastases, so the treatment should first take high-dose chemotherapy. Wittig et al. 2002 reported that the use of neoadjuvant chemotherapy resulted in limb-sparing surgery in 90-95% of patients with osteosarcoma, with a five-year survival rate of 60%-80%. 2.Guiding postoperative chemotherapy by assessing the effect of preoperative chemotherapy: the histological response of the tumor to chemotherapy is the most important factor affecting long-term prognosis, and those found to have poor response in neoadjuvant chemotherapy are switched to other cytotoxic drugs after surgery (salvage chemotherapy). Neoadjuvant chemotherapy emphasizes preoperative chemotherapy for 6-10 weeks, followed by tumor resection and postoperative chemotherapy regimens based on the degree of tumor tissue necrosis. If the tumor necrosis rate is greater than 90%, the five-year survival rate can reach 80%-90% if the original chemotherapy program is continued after surgery; while the five-year survival rate is less than 60% if the necrosis rate is less than 90%, the postoperative chemotherapy program should be adjusted. 3.Reduce the tumor and the reactive zone around the tumor to improve the limb preservation surgery: high-dose chemotherapy can kill the tumor cells in several levels, the primary foci occur in a large area of necrosis, the tumor volume is reduced, which reduces the chance of tumor cell spread during surgery, the reactive edema zone around the tumor is reduced, the blood vessels are reduced, the cutting edge is safer, more muscles can be preserved, and the function of limb preservation surgery is good and the chance of recurrence is small. 4. Allow sufficient time to design limb preservation plan and make prosthesis: the site, scope and nature of bone tumor are not exactly the same in each case, so it is difficult to prepare prosthesis with uniform standard. During the time of preoperative chemotherapy, it is possible to carefully design the prosthesis and surgical plan for the patient without delaying the patient’s treatment.