In this chapter, we will review studies of HER2 in osteosarcoma and discuss the controversies that have existed in this field. Our present understanding of HER2 in the context of osteosarcoma is that it is expressed on a subset of patient samples, but that expression is not prognostic. We will review the two trials that have been conducted in osteosarcoma which have targeted HER2. Use of an antibody, trastuzumab, did not suggest activity, but a smaller study using HER2-targeted CAR T cells suggested activity may be present. A trial of an antibody-drug conjugate targeting HER2 for recurrent osteosarcoma is under consideration. Trials targeting other surface proteins for the treatment of osteosarcoma have occurred or are in development. Indeed, this leads us to discuss in a broader fashion therapeutic approaches to targeting surface proteins. It is hoped that some of these approaches will lead to new effective therapies for patients with osteosarcoma.
Keywords: Antibody–drug conjugates; CAR T cells; HER2; Pathogenesis; Prognostic markers; Targeted therapy; Trastuzumab.