Randomized Study Comparing the Effect of Dasatinib and Imatinib on Malignant Stem Cells in Chronic Myeloid Leukemia

Inclusion Criteria:

* Patients are able to provide written informed consent
* Patients must have CML in CP which is defined by the presence of all of the following criteria:

  * \< 15% blasts in peripheral blood (PB) and BM.
  * \< 30% blasts plus promyelocytes in PB and BM.
  * \< 20% basophils in the PB.
  * ≥ 100 x 109/L platelets.
  * No evidence of extramedullary leukemia apart from hepatosplenomegaly
  * Ph+ or variants must be demonstrated by BM cytogenetics, FISH or PCR.
  * Previously untreated CML in CP, with the exception of hydroxyurea or anagrelide
* Patients must be enrolled in this study within 90 days after the date of first being diagnosed with CML
* ECOG Performance Status (PS) Score 0 - 1 (see Appendix 2)
* Adequate hepatic function defined as: total bilirubin ≤ 2.0 times the institutional upper limit of normal (ULN) in absence of Gilbert type unconjugated hyperbilirubinemia; alanine aminotransferase (ALAT≤ 2.5 times the institutional ULN.
* Adequate renal function defined as serum creatinine ≤ 2 times the institutional ULN.
* Men and women, ages 18 years and older.
* Adequate BM aspiration sample before the start of study treatment (i.e sample is sufficient for stem cell analysis)
* Potentially fertile women must use an adequate method of contraception to avoid pregnancy throughout the study.
* Potentially fertile women must have a negative serum or urine pregnancy test

Exclusion Criteria:

* Fertile women who are unwilling or unable to use an acceptable method to avoid pregnancy for the entire study
* Women who are pregnant or breastfeeding.
* Men with fertile sexual partners who can or will not use an acceptable contraception method for the entire study
* A serious uncontrolled medical disorder or active infection that would impair the ability of the subject to receive protocol therapy.
* Known pleural effusion at baseline.
* Uncontrolled or significant cardiovascular disease
* History of significant bleeding disorder unrelated to CML, including:
* Prior chemotherapy for peripheral stem cell mobilization.
* Inadequate BM aspiration sample due to marrow fibrosis or other reasons
* Prior or concurrent malignancy
* Severe psychiatric illness, imprisonment or mental impairment inflicting on ability to give informed consent
* Abuse of alcohol, prescribed or illicit drugs
* Evidence of digestive dysfunction that would prevent administration of study therapy by mouth.
* Prohibited Treatments and/or Therapies

  * Any prior treatment with interferon
  * Any prior treatment with dasatinib
  * Any prior treatment with imatinib
  * Any other prior systemic treatments, with anti-CML activity \[except for anagrelide, or hydroxyurea (HU)\].
* Patients currently taking drugs that are generally accepted to have a risk of causing Torsades de Pointes as described in Appendix 3.