[Comparative analysis of blast immunophenotype between the diagnosis and relapse of childhood acute lymphoblastic leukaemia - implications for monitoring of minimal residual disease].

PURPOSE: The aim of the present study was to compare the blast immunophenotype of acute lymphoblastic leukaemia (ALL) at diagnosis and at relapse and to define the most frequent shifts in marker expression.

PATIENTS AND

METHODS

Bone marrow samples from 14 patients were analyzed by flow cytometry both at diagnosis and at relapse - in 12 patients with B-cell precursor (BCP)-ALL and in 2 patients with T-ALL.

RESULTS

The conversion in blast immunophenotype was observed in 12 out of 14 patients (86%). Antigen CD34 turned out to be the most unstable antigen - the shift in the signal expression was present in 57% of BCP-ALL and in both T-ALL cases. Regarding B-lineage markers, the shifts most frequently concerned CD20 (shifts present in 41.5% of cases) and CD22 (27%). Among the T-lineage markers: CD3, CD4 and CD8 demonstrated the highest incidence of altered signal expression. On the other hand, the most stable antigen included CD19 and CD10 for the BCP-ALL group and CD1a, CD2, CD5, CD7 for T-ALL patients. Expression of HLA-DR, TdT and CD45 antigens remained unchanged in both BCP-ALL and T-ALL groups.

CONCLUSIONS

The results of the present study support the requirement to monitor at least two different leukaemia specific antigen combinations for detection of MRD to prevent a false-negative result and to increase the effectiveness of monitoring minimal residual disease.