The Significance Of Flow Cytometry To Monitor Minimal Residual Disease In Prognosis Of Acute Myeloid Leukemia

Objective: The main root of recurrence of leukemia patients after complete remission is minimal residual disease(MRD)persisting in bone marrow.Most of scholars choose some point detecting MRD after chemotherapy,but less on MRD in the tendency of the research in the process of chemotherapy.The purpose of the study lies in the sequential multi-points monitoring MRD after CR and consolidation and analyzing relations between MRD and recurrence.Further exploring MRD in the development of the course,the value of clinical efficacy and prognosis.Methods: Fifty one AML patients with complete remission were retrospectively analyzed from September 2012 to December 2016 in the affiliated hospital of Qingdao university.All patients received standard chemotherapy and MRD was detected three time points after induction chemotherapy,first consolidation and second chemotherapy respectively.Bone marrow morphology was checked simultaneously.The end point of Follow-up was 12 months after CR or recurrence of bone marrow.According to MRD cut-off,AML patients are divided into four groups: MRD≦10-4,10-4<MRD<10-3,10-3≦MRD≦10-2,MRD>10-2.Different time points of MRD were evaluated for its value of the prognosis in AML patients.MRD > 10-4 is defined as positive for minimal residual disease.Results:MRD level in 51 AML patients who achieve complete remission after induction chemotherapy is 4.97% maximum,0.0062%minimum,respectively,average level is 0.57%.MRD level after one cycle of consolidation therapy is measured 4.72% maximum and 0.0053% minimum,respectively,average is 0.38%.MRD was greater than 10-4 in 47 AML patients after achieving complete remission of induction chemotherapy.MRD is negative(≦10-4)in 4 cases of AML patients after complete remission.MRD measured 3.11%maximum,0.0037% minimum,average 0.21% after second consolidation therapy.MRD in 5 patients tran after second course of consolidation chemotherapy,By choosing different time points after 12 months follow up,BM morphological relapse are: one case in MRD≦10-4 group(1.96%),6 cases in 10-4 < MRD< 10-3 group(11.76%),10 cases in10-3≦MRD≦10-2 group(19.61%),16 cases in MRD>10-2group(31.37%),respectively.Relapse-free survival(RFS)of four groups were analysed with Kaplan Meier method.The differences of four groups were statistically significant(P﹤0.05).MRD≦10-4 group,10-4 <MRD <10-3 group,10-3≦MRD≦10-2 group,MRD>10-2 group,the median average relapse-free survival were 23.1months and 14.3months,9.1 months and 3.5 months,respectively.Conclusion: 1.MRD is one of the important indexes which predicts remission and relapse of acute myeloid leukemias.Dynamic monitoring of MRD with FCM after AML CR may provide clinical basis for individual therapy and prognosis.2.MRD value changed individualy so it can not be as a single index for clinical prognosis.3.MRD can be used as the sensitive indexe for evaluation of prognosis.The probability of relapse was lower when MRD was less than 10-4,the probability of relapse was higher if MRD greater than 10-4,and the lower the MRD value the longer relapse-free survival.