Development of acute lymphoblastic leukemia following treatment for acute myeloid leukemia in children with Down syndrome: A case report and retrospective review of Children's Oncology Group acute myeloid leukemia trials.

Children with Down syndrome have a 150-fold increased risk of developing acute myeloid leukemia (AML) and 20-fold increased risk of developing acute lymphoblastic leukemia (ALL). Although the risk of developing AML and ALL is significantly increased in children with Down syndrome, the development of both malignancies in the same patient is very rare. We describe a patient with Down syndrome who developed ALL 6 years after being diagnosed with AML. We performed a literature review and Children's Oncology Group query and discovered eight published cases and five cases of ALL following AML in pediatric patients with Down syndrome, as well as six cases of ALL following AML in non-Down syndrome patients. There was a similar cumulative incidence of ALL after treatment for AML in the Down syndrome and non-Down syndrome populations. Overall survival in patients with Down syndrome who developed ALL after treatment for AML was comparable to overall survival for patients with Down syndrome with de novo ALL with an average follow-up of 7 years after ALL diagnosis. Clinical data collected were used to discuss whether this phenomenon represents a secondary leukemia, second primary cancer, or mixed-lineage leukemia.