We identified a novel germline mutation in the PTPRD gene in three of eight patients (37.5%) with metastatic Ewing sarcoma….Of interest, two of three patients with germline PTPRD mutations achieved durable complete responses following treatment with IGF-1R monoclonal antibody-based therapies...Patients with Ewing sarcoma tested for germline mutations in PTPRD and outcomes with IGF-1R-based therapy.