High Progenitor Cell Frequency at Diagnosis Predicts High Minimal residual Disease Level in Childhood ALL.

Abstract 4705

Acute lymphoblastic leukemia (ALL) as the most frequent childhood malignancy exhibits a favorable prognosis, yet a significant proportion of patients suffer a relapse. Comparable to acute myeloblastic leukemia, immature leukemic cells may be resistant to therapy and initiate a new population of leukemic cells. 42 patients with childhood ALL treated according to the ALL-BFM 2000 protocol were included in the present study. We determined an aberrant immunophenotype of the leukemic population at diagnosis and investigated the expression of CD34, CD38 and CD45 in leukemic blasts. The fraction of immature leukemic cells defined by CD34+/CD38-/CD45low at time of diagnosis as well as level of minimal residual disease (MRD) at day 33 and day 80 was determined. This is the first study to show a significant correlation of the initial fraction of immature leukemic cells with minimal residual disease levels at day 33 and day 80 in childhood ALL. Thus the initial level of this CD34+/CD38-/CD45low population may serve as marker for adverse prognosis in pediatric ALL.