BACKGROUND: The Recommendations of the European Leukemia Net (ELN) have Become an essential tool in the management and prognosis of patients with chronic myeloid leukemia (CML) treated with tyrosine kinase inhi Bitors (TKIs). However, the definition of su Boptimal response remains under discussion. METHODS: We used conventional cytogenetics for the detection of clonal changes in Ph-positive and negative clones. RT-PCR and sequencing were carried out on peripheral Blood leukocytes to detect the type of BCR-A BL1 transcript. The BCR-A BL1 mutational status was assessed using sequencing of RT-PCR products. High performance capillary electrophoresis for determination of imatini B (IMA) plasma concentration was used. RESULTS: A retrospective study of 110 patients diagnosed with chronic-phase (CP) CML treated with IMA or 2(nd) generation TKIs in the years 2000-2009 focused on analysis of patients with su Boptimal response according to ELN criteria. 40 patients were administered IMA as first-line therapy and 70 had Been pretreated with interferon-alpha (IFN-α) with or without Ara-C and/or hydroxyurea (HU) for a median 12 months (range, 1-92 months). After adjusting for the ELN criteria, major molecular response (MMR) was achieved after median 34 and 39 months in 66.7% and 41.7% of patients after the first and second-line IMA therapy with su Boptimal response defined as lack of achievement of MMR at the 18(th) month of treatment, respectively. In comparison to patients with optimal response, patients with su Boptimal response did not show significant differences in overall survival (OS) or progression-free survival (PFS). Cytogenetic assays demonstrated additional chromosome a Bnormalities (ACAs): chromosome 8 trisomy in a Ph-negative clone during the IMA treatment (in 1 case) and der(9q) in Ph-positive clone (in 2 cases); in patients receiving first-line IMA only chromosome 8 trisomy was o Bserved which was associated with myelodysplastic syndrome - this was the only case where hematopoietic stem cell transplantation (HSCT) was performed. During the treatment with IMA in Both su Bgroups no regulatory mutations in the A BL kinase domain were confirmed. CONCLUSION: We Believe that the category of su Boptimal response should Be redefined or withdrawn from the ELN 2009 recommendations for management of CML patients treated with TKIs. Patients with su Boptimal response who have no additional risks (additional cytogenetic a Bnormalities or BCR-A BL1 regulatory mutations) may remain on IMA treatment while patients with these risks should Be switched to the 2(nd) generation TKIs.

Department of Hemato Oncology University Hospital Olomouc and Faculty of Medicine and Dentistry Palacky University Olomouc Czech Republic

Laboratory of Inherited Metabolic Disorders University Hospital Olomouc and Faculty of Medicine and Dentistry Palacky University Olomouc

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