MEMPHIS, Tenn--Children with acute lymphoblastic leukemia (ALL) who are in apparent remission but have detectable residual leukemic cells using immunologic techniques are four to nine times more likely to relapse than those with no detectable leukemic cells, says Dario Campana, MD, PhD, of St. Jude Childrens Research Hospital.
To identify leukemic cells in bone marrow aspirates, Dr. Campana and his colleagues used antibody probes coupled with fluorescent dyes to specifically tag leukemic cells. Levels of leukemic cells were then calculated using a flow cytometer. This technique can routinely detect one leukemic cell among 10,000 normal cells, which is 100 times more sensitive than conventional methods.
"These immunologic tests redefine remissions; our study shows that they also give physicians information about the likelihood of treatment success," he said.
The study was conducted in 158 children with newly diagnosed ALL who achieved complete clinical remission (Lancet, February 21, 1998). Patients were evaluated at five stages during treatment, while in remission by standard criteria. At each sampling interval, the detection of residual disease was associated with a significantly greater likelihood of treatment failure and leukemic relapse.