[Clinical significance of dynamic monitoring the minimal residual disease in childhood B-lineage acute lymphoblastic leukemia by multiparameter flow cytometry].

This study was aimed to explore the clinical significance of monitoring level of minimal residual disease (MRD) at different time point in B-lineage childhood acute lymphoblastic leukemia (B-ALL). Two hundred and six children with B-ALL were enrolled in this study from Augest 2008 to September 2011 in our hospital. MRD levels were detected by flow cytometry at day 15, 33 and week 12 after initial chemotherapy. The event-free survival (EFS) for patients based on MRD levels measured at different stages of chemotherapy were compared by Kaplan Meier analyses. The results showed that out of 206 cases 196 cases achieved complete remission (CR) after induction therapy (CR rate 95.1%), the 1- and 3-year EFS rate were (92.7 ± 1.8)% and (78.7 ± 3.7)%, respectively, and the 3-year EFS rate was (85.6 ± 4.9)% in standard risk group, (82.1 ± 5.8)% in intermediate risk group and (58.1 ± 9.2)% in high risk group, there was significant statistical difference between above mentioned 3 groups (P < 0.001). The MRD analysis at different time points showed that the higher the MRD level, the lower the 3-year EFS rate of children with ALL, in which the 3-year EFS rate of MRD ≥ 10(-2) at day 15, MRD ≥ 10(-3) at day 33 and MRD ≥ 10(-3) at week 12 were significantly lower. The MRD ≥ 10(-3) at week 12 was proven to be an independent predictor by multivariate Cox proportional-hazards regression model. The 3-year EFS rate for patients with MRD < 10(-3) and MRD ≥ 10(-3) at week 12 were (86.3 ± 4.1)% vs (55.8 ± 9.1)% (P < 0.05); 8 relapsed among 98 cases with negative MRD (MRD < 10(-4)) at day 33, 19 relapsed among 108 cases with positive MRD at day 33 between the two groups for recurrence rate has significant difference (P < 0.05). It is concluded that dynamically monitoring MRD by multi-parameter flow cytometry can precisely evaluate treatment response, judge treatment outcome and predict relapse in childhood B-ALL. The MRD 10(-2) at day 15, MRD 10(-3) at day 33 and MRD 10(-3) at week 12 should be considered as the best cut-off. MRD ≥ 10(-3) at week 12 was proven to be an independent factor of poor prognosis.