After standard multimodal therapy, the prognosis of relapsed and unresectable high-grade osteosarcoma is dismal and unchanged over the last decades.Thus, the investigators explored apatinib activity in patients with relapsed and unresectable osteosarcoma after the failure of first-line or second-line chemotherapy. Patients >14 years, progressing after standard treatment, were eligible to receive 500 mg or 750 mg of apatinib once daily until progression or unacceptable toxicity. The primary end point was progression-free survival (PFS) at 4 months. Secondary objectives were PFS, overall survival (OS), clinical benefit rate (CBR), defined as no progression at 4 months and safety.