Five-year follow-up results of imatinib 400 mg in late chronic phase chronic myeloid leukemia (CML) patients

Abstract

7041 Background: Imatinib (IM) is the drug of choice for the treatment of Ph+ CML, where a complete cytogenetic response (CCgR) is achieved in more than 80% of early chronic phase (ECP) patients, with a 6-year survival of 89%. Methods: We monitored the hematologic, cytogenetic and molecular response to imatinib in a cohort of 295 patients with Ph+ CML in late chronic phase (LCP) who were enrolled in a national prospective study of the GIMEMA CML Working Party, with focus on the rate of major molecular response and on progression-free survival and overall survival of complete cytogenetic responders. Patients were monitored for cytogenetic and molecular response every 6 months. Cytogenetics was performed on bone marrow cells with conventional methods. Molecular response was assessed on peripheral blood samples by quantitative PCR (RQ-PCR) using TaqMan methodology and expressing the results as a ratio of BCR-ABL to ABL x100. The duration of chronic phase prior to IM treatment ranged from 1 to 202 months (median 38). Treatment was IM 400 mg daily through all the study period, with a few dose increase to 600 or 800 mg. Results: 158 patients (54%) achieved a CCgR in 3 to 62 months (median 6) after the first IM dose and 124 of them (78%) are still in continuous CCgR after 5 years whereas 34 patients lost the CCgR, 23 of them within 24 months after the CCgR achievement. For the 158 patients the 5-year survival free from progression to accelerated or blastic phase is 95% and overall survival is 91%. 114 patients were evaluable for molecular response and 68% of them were in major molecular response with a BCR-ABL/ABL ratio lower than 0.05. Conclusions: We showed that for the complete cytogenetic responders progression-free and overall survival are likely to be as good as for ECP patients, suggesting that the quality of the cytogenetic response is prognostically more important than the chronic phase duration before IM start. Supported by European LeukemiaNet, COFIN 2003, AIL, AIRC. No significant financial relationships to disclose.