The current outcome of children with acute lymphoblasic leukemia (ALL) after
receiving risk-directed therapy has been substantially improved. Approximately 70-
80% of these children survive for more than 5 years without disease recurrence. But a
proportion of these patients experience relapse. Monitoring of minimal residual
disease (MRD) is an essential adjunct to early prediction of relapse and further tailored
therapy based on identification of persistent disease.
The objectives of this study are to establish incidence of MRD in Thai children
with ALL during and after remission induction therapy, and to correlate the incidence
with other standard prognostic parameters such as age, sex, white blood cell count, and
Fifty-six bone marrow samples (BMs) (day15 and day43) from 32 consecutive
children with ALL admitted and treated at Ramathibodi hospital were assessed for
MRD based on leukemia-associated immunophenotypes using sensitive, rapid, and
reproducible flow cytometric analysis (FC) which can detect 1 leukemic cell in 104
normal bone marrow cells.
A high incidence of MRD positive at day15 and day43 was found in patients in
high-risk group (66.7% and 33.3%, respectively). In comparison, only 14.3% and
9.1% of standard- and low-risk patients at day15, and 9.1% and 0% at day43 had
detectable MRD. The multivariate statistical analysis showed no correlation of MRD
to sex, age, immunophenotype, white blood cell count, DNA ploidy, Philadelphia
chromosome, and the risk group. (P>0.007).
Monitoring of MRD in Thai childhood ALL by FC method could provide
insights and information on the responsiveness to treatment of the disease. Prognostic
importance of the levels of MRD and its cut-off point for risk stratification requires
further studies with larger sample size and long-term follow-up.