Certain genetically defined cancers are dependent on a single overactive oncogene for their proliferation and survival, a phenomenon known as “oncogene addiction” that is exemplified by the BCR-ABL fusion gene in chronic myeloid leukemia as well as by mutant forms of the epidermal growth factor receptor (EGFR) gene and by the EML4-ALK fusion gene in non-small cell lung cancer (NSCLC). This evidence concerns the gene EGFR and chronic myelogenous leukemia, BCR-ABL1 positive.