Quantitative determination of plasma DNA to monitor efficiency of chemotherapy in adult acute lymphocytic leukemia patients

Objective To monitor the levels of plasma DNA in the chemotherapy process of adult patients with acute lymphocytic leukemia(ALL),and evaluate the relationship between plasma DNA level and chemotherapy efficiency.Methods Venous blood samples were taken from 55 adult patients with ALL before chemotherapy and 45 of them after one course of chemotherapy.The patients were divided into three groups according to the chemotherapy efficiency judged by bone marrow myelogram,hemogram and clinical manifestations.Eighty healthy subjects were selected as controls.The plasma DNA was extracted with magnetic beads,and the levels of plasma DNA were determined by duplex real-time PCR with the plasmid DNA as internal reference.Results The plasma DNA level [M(P25,P75)] in the patients with ALL before chemotherapy was 248.1(97.1,448.7) ng/mL,which was significantly higher than that of the control group [19.1(12.7,25.8) ng/mL,Z=8.916,P0.01].After one course of chemotherapy,the plasma DNA level was 35.5(17.7,83.0) ng/mL,which was markedly lower than that before chemotherapy(Z=6.322,P0.01).There was significant difference of plasma DNA levels among the three groups with different curative effect whether before chemotherapy(χ2=6.960,P0.05) or after chemotherapy(χ2=11.145,P0.01).However,there was significant difference of plasma DNA levels before and after chemotherapy(Z=3.92,P0.01) in the complete remission group,but no significant difference in the partial remission group and non-remission group.The analysis of Kaplan-Meier survival curves showed that the survival rate of patients with plasma DNA less than 50 ng/mL was higher than that of patients with plasma DNA more than or equal to 50 ng/mL(χ2=3.860,P0.05) after one course of chemotherapy.Conclusions The determination of plasma DNA level may have important significance for evaluating the curative effect and prognosis of acute lymphocytic leukemia.The reduced level of plasma DNA may predict a good prognosis.