Quantitative analysis of minimal residual disease by flow cytometry assay and its clinical significance in patients with acute leukemia

Objective To investigate the clinical significance of flow cytometry(FCM) assay in following up of the minimal residual disease (MRD) changes in 53 cases with acute leukemia (AL).Methods Bone marrow aspirates were collected from forty-three patients with newly diagnosed AL after induction therapy and during continuation therapy.The cells with leukemia associated with immunophenotypes were investigated using FCM,as immunologic target of MRD. At last,the results were compared with those from the traditional bone marrow cells morphology. Results The average sensibility and specificity to predict relapse of patients in the group of CR 1～5 months were 100%(13/13) and 76.6% (23/30),in the group of CR 6～11 months 100% (4/4 ) and 87% (20/23),and in the group of CR 12 months～100% (2/2 ) and 100% (13/13),respectively.The results of MRD positive were earlier in predicting the relapse than those of the traditional bone marrow cells morphology assay by an average of 4 months. MRD cells were quantitated when induction therapy achieved CR in 43 cases: (1) MRD was negative at CR in 25 cases, 16 of them were kept negative during following-up,and 9 cases turned to positive during following-up and after intensified chemotherapy, MRD decreased to negative,the disease relapsed in 6 of 9 cases during following-up,3 were CNSL. (2) MRD was positive at CR in 18 cases, in 10 cases of them the mean level of MRD was 2.20% at CR, decreased gradually and turned negative finally.MRD level of 8 cases was high at CR or persistently high, the disease relapsed in all these 8 cases.(3) The average amount of MRD cell was 0.48% in marrow relapse group (19 patients) at CR and 0.06% in non-relapse group (24 patients) (P0.05). Conclusion The application of FCM in detecting MRD in AL is very simple,fast,effective,sensitive and mini-traumatic,the accuracy can be further improved by means of continous and regular monitoring and dynamic analysis. It has important clinical significance in guiding chemotherapy,predicting relapse and selecting in dividualized treatment.