The Outcome of Unselected Patients with Chronic Myeloid Leukemia (CML) In Chronic Phase (CP) Treated with Imatinib In the First Line and the Prognostic Value of ELN Defined Responses – Population Based Analysis of 458 Patients Treated Between 2003–2009.

Imatinib (IM), a selective BCR-ABL tyrosine kinase inhibitor (TKI), is a treatment of choice for newly diagnosed chronic myeloid leukemia (CML) patients (pts) in chronic phase (CP) as it was shown in the IRIS trial. The treatment strategy and response evaluation is based on NCCN or ELN guidelines. Only limited “real life” data of IM impact on pts outcome as well as ELN (European LeukemiaNet) recommendations applicability in daily practice has been published. In the Czech as well as in the Slovak Republic (15 million inhabitants), the treatment of CML patients is centralized in overall 13 centers, capable carrying on both the treatment and laboratory monitoring. There are two CML prospective projects CAMELIA and INFINITY focused on CML pts analysis. Aims. To analyze the treatment response and long-term outcome in consecutive, unselected patients with CP-CML treated with IM and to evaluate the prognostic role of ELN 2006 and 2009 response evaluation. To analyze molecular response in more detail.

Altogether 458 consecutively included patients in INFINITY (152 pts) and CAMELIA projects (306 pts) were assessed. For the treatment response evaluation the ELN 2006 and ELN 2009 definitions were used. We assessed rates and the cumulative incidences of complete hematologic responses (CHR), complete cytogenetic responses (CCyR), major (MMoR) and complete molecular responses (CMoR). Overall survival (OS) was defined as the time from the start of IM to death from any cause, overall survival CML-related death (OS_CML), transformation-free survival (TFS) as survival without evidence of AP or BP or death from any cause, progression-free survival (PFS) as survival without evidence of AP or BP, loss of CHR, MCyR, increasing white blood cell count or death fron any cause while on IM treatment and event-free survival (EFS) –events defined as a progression (the same as in PFS, as described above), loss of CCyR, failure to achieve CHR at 6 months, MCyR at 12 months and CCyR at 18 months, or intolerance of IM as the cause its discontinution. The patient survival according to MMoR achievement and the cumulative incidence of MMoR according to different BCR-ABL ratio within the first 3 months of IM therapy was analysed. Kaplan-Meier cumulative incidence methods and log rank test were used for survival statistic analysis.

A total of 458 patients (median age 52 year;17-81) treated with IM between 2003–2009 were analysed.The median follow-up was 33.1 months (1.4-82.1). At 2 and 4 years the cumulative incidence of CHR was 90.9% and 94.7%, CCyR 64.9% and 76%, MMR 52.4% and 68.1% and CMR 24.5% and 43%, respectively. In 4 years estimated OS was 91.1%, OS_CML 96.6%, TFS 93.9%, PFS 83.2% and EFS 66%. According to ELN 2006 criteria the optimal response (OR) by 6 months (defined as PCyR) and by 12 months (defined as CCyR) resp. had significant impact on PFS (p=0.04 and p<0.001 resp.). The optimal reponse by 3 months (defined as CHR) had significant impact on TFS (p<0.001). According to actualized criteria in ELN 2009, the new definition of optimal response in the 3^rd month - at least minor cytogenetic response (mCyR), did not show any prognostic impact on PFS. The achievement of MMoR was correlated with the significant improvement in PFS in the 3^rd month (p=0.039) as well as in the 12^th month (p<0.049). There was significant improvement in EFS for patients in MMoR in all timepoints (p<0.003, <0.001, <0.001, <0.005). The BCR-ABL ratio lower than 1% within the first 3 months was associated with MMoR achievement in higher number of patients in comparison to patients with higher BCR-ABL levels (p<0.001)

The excellent and long-lasting efficacy of imatinib in the treatment of CP-CML in non-selected group of patients treated in the defined region was confirmed. Our results are comparable to those achieved in IRIS trial. Response criteria and their predictive role defined by ELN 2006 and 2009 seems to be helpful at some time points, but the ELN 2009 modification does not seem to represent significant improvement compared to ELN 2006. On the other hand based on the present analysis the earlier incorporation of molecular response into the evaluation scheme may be beneficial.

CELL-The Czech Leukemia Study Group for Life, Project INFINITY; Project CAMELIA.

Faber:BMS, Novartis: Consultancy, Honoraria.