Survival Outcomes of Children with Relapsed or Refractory Myeloid Leukemia Associated with Down syndrome.

Children with Down syndrome (DS) are at a significantly higher risk of developing acute myeloid leukemia, also termed myeloid leukemia associated with DS (ML-DS). In contrast to the highly favorable prognosis of primary ML-DS, the limited data that are available for children who relapse or who have refractory ML-DS (r/r ML-DS) suggest a dismal prognosis. There are few clinical trials and no standardized treatment approach for this population. We conducted a retrospective analysis of international study groups and pediatric oncology centers and identified 62 patients who received treatment with curative intent for r/r ML-DS between 2000-2021. Median time from diagnosis to relapse was 6.8 (range 1.1 - 45.5) months. Three-year event-free (EFS) and overall survival (OS) were 20.9±5.3% and 22.1±5.4%, respectively. Survival was associated with receipt of hematopoietic stem cell transplantation (HSCT) (HR 0.28), duration of first complete remission (CR1) (HR 0.31 for > 12 months) and attainment of remission after relapse (HR 4.03). Patients who achieved CR prior to HSCT, had an improved OS and EFS of 56.0±11.8% and 50.5±11.9% respectively, compared to those who underwent HSCT without CR (3-year OS and EFS of 10.0±9.5%). Treatment failure after HSCT was predominantly due to disease recurrence (52%) followed by treatment related mortality (10%). The prognosis of r/r ML-DS remains dismal even in the current treatment period and serve as a reference point for current prognostication and future interventional studies. Clinical trials aimed at improving the survival of patients with r/r ML-DS are needed.