Imatinib (IM) is first-line treatment for patients with newly diagnosed CML in chronic phase. The drug is associated with high rates of cytogenetic responses with minimal toxicity in approximately 80% of patients. In 20% of patients however, the disease is either initially unresponsive to IM (Imatinib), resistance develops within a few months, or blast crisis occurs early and unexpectedly following an initial response. An increasing body of clinical evidence indicates that single agent molecularly targeted therapy (as in Gleevec/Imatinib) will not cure most patients with CML, as molecular remissions are rare. There is currently no clinically useful predictive tests to identify AT DIAGNOSIS those patients who are destined to be IM failures. The authors of this study have recently demonstrated that CML stem/progenitor cells are biologically insensitive to IM and are also genetically unstable and rapidly generate IM-resistant mutants in vitro and in vivo. The team recently discovered that the CD34 stem/progenitor cells of newly diagnosed CML patients who subsequently fail to respond to IM treatment show a reduced response to IM and a higher frequency of BCR-ABL mutations by comparison of 14 IM non-responders with 11 IM-responders. If this finding can be validated in a larger prospective cohort of patients, this predictive test could be used to more rationally design treatment plans with early addition of alternative therapies ie: Dasatinib or combination therapies for patients according to their individual risk profiles.