IGF1R and cancer: At least 50% of breast tumors have an activated type 1 insulin-like growth factor-1 receptor (IGF-1R).1 Several preclinical investigations have associated the activation of IGF-1R by its two natural ligands, insulin-like growth factor-1 (IGF-1) and IGF-2,2 as primary risk factors in various types of human diseases3 including cancer.4 A case for targeting IGF-1R was based on several observations.