High EVI1 Expression Predicts Outcome in Younger Adult Patients With Acute Myeloid Leukemia and Is Associated With Distinct Cytogenetic Abnormalities

PURPOSE The purpose of this study was to investigate frequency and prognostic significance of high EVI1 expression in acute myeloid leukemia (AML). PATIENTS AND METHODS A diagnostic assay detecting multiple EVI1 splice variants was developed to determine the relative EVI1 expression by single real-time quantitative polymerase chain reaction in 1,382 newly diagnosed adult patients with AML younger than 60 years. Patients were treated on four Dutch-Belgian HOVON (n = 458) and two German-Austrian AML Study Group protocols (n = 924). Results The EVI1 assay was tested in the HOVON cohort and validated in the AMLSG cohort. High EVI1 levels (EVI1(+)) were found with similar frequencies in both cohorts combined, with a 10.7% incidence (148 of 1,382). EVI1(+) independently predicted low complete remission (CR) rate (odds ratio, 0.54; P = .002), adverse relapse-free survival (RFS; hazard ratio HR, 1.32; P = .05), and event-free survival (EFS; HR, 1.46; P < .001). This adverse prognostic impact was more pronounced in the intermediate cytogenetic risk group (EFS; HR, 1.64; P < .001; and RFS; HR, 1.55; P = .02), and was also apparent in cytogenetically normal AML (EFS; HR, 1.67; P = .008). Besides inv(3)/t(3;3), EVI1(+) was significantly associated with chromosome abnormalities monosomy 7 and t(11q23), conferring prognostic impact within these two cytogenetic subsets. EVI1(+) was virtually absent in favorable-risk AML and AML with NPM1 mutations. Patients with EVI1(+) AML (n = 28) who received allogeneic stem cell transplantation in first CR had significantly better 5-year RFS (33% +/- 10% v 0%). CONCLUSION EVI1 expression in AML is unequally distributed in cytogenetic subtypes. It predicts poor outcome, particularly among intermediate cytogenetic risk AML. Patients with EVI1(+) AML may benefit from allogeneic transplantation in first CR. Pretreatment EVI1 screening should be included in risk stratification.