Flow cytometry as a predictive modality for translocation (9;22) and translocation (12;21) in B acute lymphoblastic leukemia

Background
Cytogenetic aberrations are recognized to be an important determinant of the biological and clinical features in acute lymphoblastic leukemia (ALL). Also, they have prognostic impact and are important for stratifying patients into risk groups and tailoring treatment accordingly. However, these investigations are costly and time consuming.


Objectives
The purpose of this study was to predict the major chromosomal translocations in ALL, namely t(9;22)(q34;q11) and t(12;21)(p13;q22), on basis of the immunophenotypic markers (CD66c, CD10, CD25, CD34 and CD38).


Patients and methods
A total of 52 newly diagnosed Egyptian patients with ALL were evaluated by flow cytometry. Fluorescence in situ hybridization was performed for detection of the expression of t(9;22)(q34.1;q11.2); BCR-ABL1 and t(12;21)(p13.2;q22.1); ETV6-RUNX1 on bone marrow samples collected from the patients at diagnosis. We investigated the association between defined cytogenetic abnormalities revealed by Fluorescence in situ hybridization and selected immunophenotypic markers.


Results
Of these 52 cases, 11 patients were positive for t(9;22)(q34.1;q11.2); BCR-ABL1 and seven patients were positive for t(12;21)(p13.2;q22.1); ETV6-RUNX1. Genotype-phenotype association showed that CD33, CD25 and CD34 expression was significantly highly expressed in t(9;22) positive cases compared with negative cases (P=0.007, P=0.002, and 0.048, respectively). However, CD38 was significantly higher in t(9;22) negative cases (P=0.034). Multivariate analysis highlighted the robust predictive value of CD25 in prediction of t(9;22). Unfortunately, no significant association was detected regarding immunophenotypic markers and t(12;21).


Conclusion
Predictive probabilities of t(9;22) by immunophenotypic markers are proposed. There is a significant association between some immunophenotypic markers (CD33, CD34, CD38, and CD25) and t(9;22). Whereas the finding does not replace the detection of t(9;22) abnormality by cytogenetic or molecular techniques, it provides an early tool for prediction of high risk cases of B-ALL.