Effect of Previous Use of Hydroxyurea on the Formation of Response to Tyrosine Kinase Inhibitor Therapy in Patients with Chronic Myeloid Leukemia

The objective of the study was to establish the role of prior use of hydroxyurea in shaping of the response to tyrosine kinase inhibitors therapy (TKI) in patients with chronic myeloid leukemia (CML). Patients were divided into 2 groups depending on the duration of the drug application. The first group included 134 patients treated with hydroxyurea no more than 6 months, the second - 253 patients who were treated with these drugs for more than 6 months before the appointment of imatinib. Studies indicate that the previous use of hydroxyurea no more than 6 months leads to the optimal response after 12 months imatinib treatment in (71.6±3.9)% of patients, to suboptimal in (17.2±3.3)%, to treatment failure in (11.2±2.7)% of patients. Study of imatinib treatment in patients who previously received hydroxyurea for more than 6 months, showed that at 12 months therapy the optimal response was achieved in (13.0±2.1)% of patients, suboptimal response defined in (29.6±2.9) %, treatment failure - in (57.3±3.1)%. It is proved that the previous use of hydroxyurea over the 6 months before prescribing TKI leads to poor response to therapy. Thus, hydroxyurea pretreatment >6 months is one of the factors that degrade the results TKI therapy and may be the cause of resistance to treatment.