The patient will be followed until major molecular response (MMR) is re-achieved and further 6 months beyond. Date of progression, hematological data at progression (molecular, cytogenetic, and hematological), and treatment proposed for molecular progression and response to it (molecular, cytogenetic, hematological) will be collected. Follow-up for overall survival (OS) and progression-free survival (PFS) will last 2 years since the date of switch of TKI.