Text Box: SIGNIFICANCE AND RELATIONSHIP BETWEEN RELAPSE AND MINIMAL RESIDUAL DISEASE IN ACUTE LYMPHOBLASTIC LEUKEMIA 
Li Wenyi, Xia Yan, Guo Haixia, Den Qingli, Fang Jianpei, Xue Hongmang, Zhou Dunhua 
Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University of Medical Sciences, Guangzhou, China

Objective: To explore clinical significance and analyze the level or changes of minimal residual disease (MRD) correlated with relapse in acute lymphoblastic leukemia (ALL).  
Methods: A modified limiting dilation assay and nested-PCR was applied in this study, Kaplan-Meier method and COX model were applied to analyze the data.  
Results: Among 46 cases of ALL, the level of MRD by the time of complete remission (CR) positively correlated with relapse (γ=0.4696,P<0.05). There was statistic difference of the level of MRD between non-marrow relapse group and marrow relapse group in which the level of MRD was 7.3χ10-3. During the period of CR, the cases whose MRD was persistently positive or form negative to positive, had high possibility at relative risk for relapse (P<0.05). 
Conclusion: Minimal residual disease by the time of CR is a powerful prognostic factor in ALL, detection of MRD by PCR should be used to identify patients at risk for relapse and dynamic monitoring MRD could be valuable in guiding the management of ALL and predicting relapse.

Key words: acute lymphoblastic leukemia; minimal residual disease; relapse
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