IGF1R and Ewing sarcoma: Despite significant preclinical activity of an IGF1R inhibitor in Ewing’s sarcoma models, the inhibitor and anti-IGF1R monoclonal antibodies cixutumumab and ganitumab have demonstrated only modest or partial response in a subset of patients [51], suggesting that a biomarker to predict responsiveness to IGF1R inhibition may be required for patient selection.