High EVI1 Expression Predicts Outcome in Younger Adult (15 to 60 years) Patients with Acute Myeloid Leukemia and Is Associated with Distinctive Cytogenetic Subgroups.

Untying the heterogeneity of acute myeloid leukemias (AML) remains a major challenge for the development of accurate clinical classification, risk stratification, and therapy of the disease. In spite of the fact that molecular insight of AML has increased tremendously, the discovery and validation of novel discriminative biomarkers is of utmost value for better outcome prediction. Overexpression of the ecotropic viral integration 1 gene (EVI1⁺) occurs in ∼8% of adult AML, and it is presumed that EVI1 plays a major role in the pathogenesis of a subset of high-risk leukemias. Quantitative measurement of EVI1 has been complicated due to the existence of various EVI1 5'-splice variants. To overcome this complexity, we established one standardized quantitative real-time PCR (qPCR) assay allowing for comprehensive splice variant quantification, and determined the clinical impact of EVI1⁺ in younger adult AML patients (15-60 years) in the context of established cytogenetic and molecular markers.

The expression of EVI1 was determined in 1,382 newly diagnosed AML patients treated on four Dutch-Belgian HOVON (04/A, 29, 42; n=458) and two German-Austrian AMLSG (HD98A, 07/04; n=924) protocols. Selection was based on availability of blood or bone marrow specimens for analysis. An EVI1 overexpressing ovarian cancer cell line (SKOV3) was used for relative quantification.

The EVI1 diagnostic assay identified all previously reported EVI1⁺ patients within the HOVON cohort (44/458; 10%) (Lugthart et al; Blood 2008). The incidence of EVI1⁺ in the AMLSG cohort was comparable (104/924; 11%). Therefore, both cohorts were combined for further analyses. Overall, 148 of 1,382 (11%) AML cases were identified as EVI1⁺. Cytogenetic abnormalities significantly over-represented among EVI1⁺ cases included inv(3)/t(3;3) (15%), other 3q26 abnormalities (4%), non-complex -7 (12%) and 11q23 translocations (22%). The favorable cytogenetic abnormalities were significantly under-represented in EVI1⁺ patients: EVI1⁺ was not found in core-binding factor leukemias, and occurred in 1/148 (1%) t(15;17) leukemia. In contrast, the unfavorable cytogenetic abnormalities, i.e. inv(3)/t(3;3), t(6;9), 11q23 translocations except t(9;11), -5/5q-, -7, and complex karyotype accounted for 54% of the EVI1⁺ AMLs (P<.001). The intermediate cytogenetic abnormalities, i.e. normal karyotype AML and aberrations that do not classify as favorable or unfavorable cytogenetic groups, accounted for 45% of the EVI1⁺ patients. This included 21% (31/148) normal karyotype AML, with only 2 cases displaying the NPM1^mut/FLT3-ITD^neg favorable molecular genotype (P<.0001). EVI1⁺ patients had a significantly inferior event-free (EFS; P<.0001), relapse-free (RFS; P<.0001), and overall survival (OS; P<.0001). In multivariable analysis, EVI1⁺ predicted a low complete remission (CR) rate (OR=0.54, P=.002), as well as poor RFS (HR=1.32, P=.05) and poor EFS (HR=1.46, P=.0003) independently of other prognostic features. The independent prognostic value of EVI1⁺ was also found in patients with intermediate cytogenetics, for EFS (HR=1.64, P=.0006) and RFS (HR=1.55, P=.02). Furthermore, the adverse effect of EVI1⁺ on OS was seen in two major cytogenetic subgroups over-represented in EVI1⁺ patients: non-complex -7 with 2-year survival rate of 0%, and 11q23 translocations with 2-year survival rate of 7% (95%-CI 0–27%, P=.03). Importantly, EVI1⁺ patients (n=28) who received allogeneic stem cell transplantation from matched related or unrelated donors in first CR had a significant better survival (RFS, P=.001; OS, P=.05).

We developed a rapid and reproducible EVI1 specific pre-treatment qPCR assay and showed that EVI1⁺ is associated with unfavorable cytogenetic and molecular genetic AML. EVI1⁺ independently predicts for low CR rate, EFS, and RFS in the overall cohort. Nevertheless, EVI1⁺ adds independent adverse prognostic value for EFS and RFS in the intermediate-risk cytogenetic group. Therefore, EVI1⁺ appears as a useful prognostic biomarker in this large heterogeneous AML subgroup. The observations that EVI1⁺ may define prognostic subgroups within specific cytogenetic subsets, and that EVI1⁺ AML patients may benefit from allogeneic stem cell transplantation as frontline therapy warrant further studies.

No relevant conflicts of interest to declare.