Objective. Evaluate the prognostic value of the regression of leukemic cells (LC) rate in the period from the 15th to the 36th day of the induction therapy for survival rates of children with acute lymphoblastic leucosis (B-ALL) receiving treatment according to the ALL-MB-2008 protocol. Using estimates of the rate of the LC regression and of the minimal residual disease (MRD) value on the 36th day of therapy, identify the group of patients at the highest risk of relapsing.

Materials and methods. The study included B-ALL 517 patients aged 1 to 18 years (median age — 4.16 years) lacking translocations t(9;22), t(4;11) the MRD values known on the 15th and 36th day of the induction therapy. The MRD values were determined by the 5—10 color flow cytometry. The studied patients were treated according to the ALL-MB 2008 protocol, therapy was initiated during the period from February 2008 to November 2014.

Results. The results of the study demonstrated an increase in survival rates in children with B-ALL received PEG-asparaginase. The increase in survival rates in patients with ALL received PEG-asparaginase on 3th dayof induction therapy is achieved due to a faster clearance of leukemic cells — a decrease in MRD<0.1% by day 15th of therapy.

Conclusion.The use of PEG-asparaginase did not affect the clearance of leukemic cells during the period from the 15th to the 36th day of induction therapy, and also did not affect the survival rates among patients with comparable clearance of leukemic cells at the induction therapy.The usedaunorubicin on 8th day of induction therapydid not affect the clearance of leukemic cells.