This protocol is a multicentric interventional phase II study from the French CML Intergroup (FILMC).

The core of the protocol is to explore the efficacy and safety of an optimization strategy consisting in the modulation of the dasatinib daily dose according to the results of repeated plasmatic levels of dasatinib.

The objective of this strategy is to improve the overall results of the treatment of early CP-CML in order to avoid the development of resistance and BCR-ABL tyrosine kinase mutations.

The study will be conducted in selected FILMC and Canadian centers.

The study is sponsored by the Hôpitaux de Versailles and supported by Bristol-Myers Squibb. The dasatinib treatment will be provided by Bristol-Myers Squibb until marketing authorization is granted in that indication.

Inclusion Criteria:

1. Male or female patient ≥ 18 years
2. ECOG Performance Status score 0-2
3. Philadelphia chromosome positive newly diagnosed (≤ 3 months) CP-CML
4. patients not previously treated except with hydroxyurea or imatinib (less than 4 weeks for imatinib)
5. Signed written inform consent
6. Adequate hepatic function defined as: total bilirubin ≤ 2.0 times the institutional ULN; ALT and AST ≤ 2.5 times the institutional upper limit of normal (ULN).
7. Adequate renal function defined as serum creatinine ≤ 3 times the institutional ULN.
8. Women of childbearing potential (WOCBP) must be using an adequate method of contraception.

Exclusion Criteria:

1. Patients with BCR-ABL positive, Philadelphia negative CML
2. Patient previously treated with a tyrosine kinase inhibitor (TKI) except with imatinib during less than 4 weeks.
3. Pregnancy
4. Active malignancy
5. Uncontrolled or significant cardiovascular disease
6. Patients with QTc > 450 ms
7. Significant bleeding disorder unrelated to CML
8. Concurrent severe diseases which exclude the administration of therapy