The purpose of this study is to assess the safety and efficiency of adding pioglitazone to chronic phase chronic myelogenous leukemia patients having received imatinib mesylate who have acquired a stable molecular response but not complete molecular response.

Although tyrosine-kinase inhibitors have profoundly converted the outcomes of chronic myelogenous leukemia patients ,the most of who could have a complete cytogenetic response, a large majority of patients could not come to a complete molecular response that is undetectable in breakpoint cluster region-Abelson chimeric oncogene transcripts. According to some previous researches, pioglitazone may target leukemia stem cells and induce them into cell cycle making them exit from quiescent undivided states. Subsequently, pioglitazone may gradually erode leukemia stem cells leading to undetectable minimal residual disease. Thus the investigators expect to assess the safety and efficiency of pioglitazone in combination with imatinib mesylate in clinical trials. Maybe the combination therapy induce more patients in a detectable molecular response into a deeper molecular response. Furthermore, pioglitazone may be extensively adapted into the treatment of chronic phase chronic myelogenous leukemia patients as a common protocol.

Inclusion Criteria:

1. Signed informed consent.
2. Treatment with imatinib mesylate for more than 2 years.
3. Patients with chronic phase chronic myelogenous leukemia having a complete cytogenetic response and a stable molecular response without complete molecular response.
4. Normal important organs such as kidney, liver and heart.

Exclusion Criteria:

1. Severe important organs disfunction such as liver and kidney.
2. Cardiovascular disease.
3. Osteoporosis in therapy.
4. Severe fluid retention.