Assess Long-term Feasibility of Reduced Dose Dasatinib in Chronic Phase Chronic Myeloid Leukemia Patients

Inclusion Criteria:

* Adult CML-CP Ph+ (Philadelpia) patients with BCR-ABL1 patients diagnosed within 3 months
* Adequate renal function defined as serum creatinine ≤ 3 times the institutional ULN(Upper limit of normal)
* Adequate hepatic function defined as: total bilirubin ≤ 2 times the institutional ULN; alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 times the institutional upper limit of normal (ULN).
* Adequate cardiac function (see exclusion criteria)
* Adequate pulmonary function (see exclusion criteria)
* Serum Na, K, Mg, and total serum Ca or ionized Ca levels must be greater than or equal to the institutional lower limit of normal. Subjects with low K, Mg levels, total serum Ca and/or ionized Ca must be replete to allow for protocol entry: Rescreening is permitted in the event of temporary biochemical abnormalities
* CML-CP Ph+ patients with CHR but with BCR-ABL level \< 10% IS after 3 months of frontline dasatinib 100 mg treatment. And currently persisting any grade adverse events to dasatinib 100 mg QD
* ECOG(Eastern Cooperative Oncology Group) performance status 0-2
* Women must not be pregnant

Exclusion Criteria:

* Previous diagnosis of accelerated phase or blast crisis
* Documented any major ABL1 mutation
* A serious uncontrolled medical disorder or active infection that would impair the ability of the subject to receive dasatinib
* Pulmonary arterial hypertension
* Congenital bleeding disorders
* Prior or concurrent malignancy, except for the following
* Subject with any anti-CML other than dasatinib
* Subjects with prior stem cell transplantation and/or high dose chemotherapy for CML
* Subjects currently taking drugs that are generally accepted to have a risk of causing Torsades de Pointes
* Subjects who were previously treated with over 100mg at second phase screening
* Subjects who are not tolerable to 80mg at second phase screening
* Patients who are pregnant or breast feeding or likely to become pregnant
* Prisoners or subjects who are involuntarily incarcerated
* Subjects who are compulsorily detained for treatment of either a psychiatric or physical (eg, infectious disease) illness