Dasatinib is an orally active, tyrosine kinase inhibitor that has demonstrated manageable safety and high response rates in patients with chronic phase (CP) chronic myeloid leukemia (CML). Dasatinib has shown promising therapeutic effects in CML patients, but its toxicity profile may impact its overall benefit. Long-term use of dasatinib causes pleural effusion, with higher incidence in patients over 60 years. Other significant toxicities include pulmonary hypertension, and thrombocytopenia. Study aims to design a therapeutic drug monitoring strategy for dasatinib, studying the correlation between plasma dasatinib concentrations and pleural effusion in CML patients. The study will also explore the Dasatinib pharmacokinetics to develop a population pharmacokinetic model of dasatinib in adult and paediatric CML patients. In this study, patients will be followed for a maximum of 24 months from the start of dasatinib. The total sample size is 174 adult CML patients and 15 paediatric patients.