To validate our hypothesis that fusion versioning may influence clinical outcome, we compared hazard ratios for EFS across the CBFB-MYH11 AML cohort as a function of fusion versions and several well-established prognostic variables, including exon 17 KIT mutation status, WBC count at diagnosis, patient age at diagnosis, and initial response to therapy as measured by end of induction 1 (EOI1) minimal residual disease. This evidence concerns the gene CBFB and acute myeloid leukemia.