Efficacy of 400 Mg Versus 800 Mg Imatinib in Chronic Myeloid Leukemia in Chronic Phase Patients - TOPS (Tyrosine Kinase Inhibitor Optimization and Selectivity)

Inclusion Criteria:

* Patients within 6 months of diagnosis (date of initial diagnosis is the date of first cytogenetic analysis)
* Diagnosis of chronic myelogenous leukemia (CML) in chronic phase with cytogenetic confirmation of Philadelphia chromosome of (9;22) translocations and presence of Breakpoint cluster region gene-abelson proto-oncogene (Bcr-Abl)
* Documented chronic phase CML
* Adequate end organ function as defined by:

  * total bilirubin \< 1.5 x Upper Limit of Normal (ULN)
  * Serum glutamic oxaloacetic transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) \< 2.5 x ULN
  * creatinine \< 1.5 x ULN

Exclusion Criteria:

* Patients in late chronic phase, accelerated phase, or blastic phase are excluded
* Patients who have received other investigational agents
* Patients who received Gleevec/Glivec for any duration prior to study entry, with the exception of those patients successfully completing \[CSTI571A2107 (NCT00428909)\] study immediately prior to the participation in this study
* Patient received any treatment for CML prior to study entry for longer than 2 weeks with the exception of hydroxyurea and/or anagrelide
* Patients with another primary malignancy except if the other primary malignancy is neither currently clinically significant or requiring active intervention
* Patients who are: (a) pregnant, (b) breast feeding, (c) of childbearing potential without a negative pregnancy test prior to baseline and (d) male or female of childbearing potential unwilling to use barrier contraceptive precautions throughout the trial (post-menopausal women must be amenorrheic for at least 12 months to be considered of non-childbearing potential).
* Patient with a severe or uncontrolled medical condition (i.e., uncontrolled diabetes,chronic renal disease)
* Patient previously received radiotherapy to ≥ 25% of the bone marrow
* Patient had major surgery within 4 weeks prior to study entry, or who have not recovered from prior major surgery
* Patients with an Eastern Cooperative Oncology Group (ECOG) Performance Status Score ≥ 3
* Patients with International normalized ratio (INR) or partial thromboplastin time (PTT) \> 1.5 x ULN, with the exception of patients on treatment with oral anticoagulants
* Patients with known positivity for human immunodeficiency virus (HIV); baseline testing for HIV is not required
* Patients with identified sibling donors where allogeneic bone marrow transplant is elected as first line treatment

Other protocol-defined inclusion/exclusion criteria applied.