BOSTONA rare pediatric leukemia, previously thought to be a subset of acute lymphoblastic leukemia (ALL), is actually a distinct form of the disease, according to investigators who used gene chips to create and contrast genetic profiles of cancer cells.
Scott Armstrong, MD, PhD, of Dana-Farber Cancer Institute, and his colleagues call the disease mixed-lineage leukemia (MLL) for a chromosomal translocation of the MLL gene.
Different Gene Expression Pattern
They reported in the January 2002 issue of Nature Genetics that the condition has a dramatically different pattern of gene expression from that of both ALL and acute myelogenous leukemia (AML), in addition to the distinguishing chromosomal translocation.
MLL affects infants in their first year; fewer than 100 babies annually are affected in the United States. It is especially aggressive, with recurrences leading to fatalities in about 60% of cases.
By 1999, a number of pediatric oncology groups had noticed that cells with the MLL translocation were more sensitive to cytarabine(Drug information on cytarabine) than other ALL cells, said Dr. Armstrong, who is also instructor in pediatric oncology, Harvard Medical School. The groups began experimenting with more intensive therapy than is standard for ALL, but have yet to determine whether outcomes are improved.
"You probably should think of treating MLL patients with hybrid therapy for ALL and AML," Dr. Armstrong told ONI. "We’re treating patients with a backbone of ALL therapy, but with much more cytarabine than normally would be used to treat ALL."