The introduction of imatinib mesylate made a remarkable contribution to the management of patients with chronic myeloid leukemia. In this study, we assessed the long-term efficacy of imatinib exposure in patients with CML in chronic phase according to European recommendations which consists both early and late chronic phase patients. This is a retrospective study including 101 chronic phase CML patients from a single center. The patient outcomes were analyzed according to initial treatment with

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... imatinib either as firstline or secondline option following prior interferon. Kaplan-Meier curves were constructed to estimate probability and differences between subgroups were analyzed by the log-rank test. Forty-three percent of the patients had a prior history of interferon therapy. Of the 101 patients included, complete cytogenetic responses were achieved in 43.6 % of patients; major cytogenetic response in 55.4%; major molecular response in 36.6%. Totally, 21.3% had cytogenetic failure and 5.3% without any hematological response. Response rates were lower in late chronic phase patients compared to early chronic phase patients. This study justified the significance of ELN criteria and once again approved the high efficacy of imatinib treatment in chronic phase CML patients.