Detection of minimal residual disease in childhood acute lymphoblastic leukemia by multi-parameter flow cytometry

Objective To establish a flow cytometric measurement of detecting minimal residual disease(MRD) according to the leukemia-associated immunophenotypes in children with acute lymphoblastic leukemia(ALL) and to explore the significance of MRD detection in ALL children for a individualized treatment. Methods A variety of four-color fluorescent antibody combinations were used to investigate the children's normal bone marrow. The normal bone marrow pattern at two-parameter plots was established to identify the residual tumor cells, seventy-five bone marrow samples from newly diagnosed ALL children were analyzed with four-color cytometry to determined the optimal combinations which can clearly distinguish the tumor cells from normal cells. The bone marrow samples were monitored with the combination panel in 60 patients at the end of induction therapy and follow-up treatment. Cytomorphology test, PCR amplification of 29 fusion genes as well as IgG and TCR gene rearrangements were performed simultaneously. Results Sixty-nine cases (92.0%) could be identified for effective antibody combinations to monitor MRD by four-color cytometry. Fusion genes or IgG and T cell receptor (TCR) gene rearrangements can be detected in 21 cases (28.0%) to monitor MRD by PCR. No MRD can be detected in 25 bone marrow samples at the end of induction therapy and follow-up treatment. Four-color cytometry could detect as low as 0.021%-4.130% residual leukemia cells. Conclusion MRD can be monitored by flow cytometry which is faster than PCR, and the sensitivity is superior to morphology method. Key words: Precursor cell lymphoblastic leukemia-lymphoma;  Neoplasm;  residual;  Flow cytometry