A Study on the Withdrawal of Second-generation Tyrosine Kinase Inhibitors After Dose Reduction in Patients With CML

Inclusion Criteria: 1. Male or female over 18 years 2. Patients diagnosed as Ph+ (or Ph- but PCR-positive for BCR-ABL) CML-CP 3. Patients have received one of the second-generation TKIs (nilotinib, dasatinib) for at least 3 years 4. Patients have maintained MMR (BCR/ABL IS\<0.1% or more) at least 2 years 5. in the past 24 months, at least three times recent molecular reactions have confirmed MMR 6. Patients have signed the informed consent Exclusion Criteria: 1. patients with the presence or history of T315I mutation 2. patients with the presence of rare unquantifiable atypical transcripts 3. Patients with comorbid cardiovascular disease or a history of severe cardiovascular disease 4. patients have history of accelerated or blast phase, or suspected blast disease 5. patients have received allogeneic hematopoietic stem cell transplantation 6. patients have severe abnormal liver and kidney function (ALT \> upper limit of normal, AST \> 3 times normal upper line, glomerular filtration rate \< 50%) 7. patients combined with other tumors or a history of other malignancies ECOG score\>3 8. Two-line abnormality in the patient's blood routine examination 9. women is pregnant or nursing