Normal karyotype is a poor prognostic factor in Myeloid Leukemia of Down Syndrome: a retrospective international study

Abstract

Myeloid leukemia of Down Syndrome has a better prognosis than sporadic pediatric acute myeloid leukemia. Most myeloid leukemia of Down syndrome cases are characterized by additional cytogenetic changes besides the constitutional trisomy 21, but their potential prognostic impact is not known. We therefore conducted an international retrospective study of clinical characteristics, cytogenetics, treatment, and outcome of 451 children with myeloid leukemia of Down syndrome . All karyotypes were centrally reviewed before assigning patients to subgroups. The overall 7-year event-free survival for the entire cohort was 78% (+/-2%), with overall survival 79% (+/-2%), cumulative incidence of relapse 12% (+/-2%), and cumulative incidence of toxic death 7% (+/-1%). Outcome estimates showed large differences across the different cytogenetic subgroups. Based on the cumulative incidence of relapse , we could risk-stratify patients into two groups: normal karyotype cases (n=103) with a higher cumulative incidence of relapse (21% (+/-4%)) than cases with an aberrant karyotype (n=255) with a cumulative incidence of relapse of 9% (+/-2%) (p=0.004). Multivariate analyses revealed white blood cell counts >/=20 x109/l and age >3 years as independent predictors for poor event-free survival event-free survival, while normal karyotype independently predicted inferior overall survival, event-free survival, and relapse-free survival. In conclusion, this study showed large differences in outcome within Myeloid leukemia of Down Syndrome patients and identified novel prognostic groups that predicted clinical outcome and hence may be used for stratification in future treatment protocols.