 This study found that a tumor microenvironment, TME, index could accurately predict the prognosis of patients with osteosarcoma and their response to immune checkpoint inhibitor, ICI, therapy. This index was composed of four genes MYC, P4HA1, RAMP1, and TAC4, which are highly expressed in the TME of osteosarcoma patients. High levels of these genes indicate a poor prognosis and a lower likelihood of response to ICI therapy. Low levels of these genes indicate a better prognosis and a greater chance of response to ICI therapy. Furthermore, the TME index was also associated with other factors such as immune cell infiltration, immune-related signature scores, and response to 29 oncologic drugs. These findings suggest that the TME index may be useful in predicting the prognosis of osteosarcoma patients and their response to ICI therapies. This article was authored by Chang Wu Wu, Simon Gong, Ying Huan Duan, and others. We are article.tv, links in the description below.