The present invention provides diagnostic and prognostic methods for predicting the effectiveness of treatment of a cancer patient with an IGF-1R kinase inhibitor. Methods are provided for predicting the sensitivity of tumor cell growth to inhibition by an IGF-1R kinase inhibitor, comprising assessing whether the tumor cell has undergone an epithelial to mesenchymal transition (EMT), by determining the expression level of epithelial and/or mesenchymal biomarkers, wherein tumor cells that have undergone an EMT are substantially less sensitive to inhibition by IGF-1R kinase inhibitors. Improved methods for treating cancer patients with IGF-1R kinase inhibitors that incorporate the above methodology are also provided.