2. DFS - 85,0±6,8% (n=108; ev=6)

4. STANDARD-RISK GROUP (SR) if available FC MRD < 0,1% or M1/ M2 marrow on day 15 HIGH-RISK GROUP (HR) IR and, if available FC MRD >10% or M3 marrow on day 15 SR if available FC MRD >10% INTERMEDIATE-RISK GROUP (IR) All patients who are not stratified to SR or HR are intermediate risk patients.

5.  Identify residual leukemia blasts in blood and bone marrow by microscopic analysis on 15 and 33 days.  Morphological assessment can be imprecise.  Measurement of MRD can be used to monitor treatment response much more precisely than morphological screening.

6.  Using 3-color flow cytometry on 15 day CD19 + CD10 + 13,6% NC CD19 + CD10 + CD58 ++ 13,6% NC CD19 + CD34 + 0,06% NC CD19 + CD34 + CD58 ++ 0,06% NC

7.  67 patients  64 patients with immunophenotype pre-pre B  2 patients with pro B immunophenotype  1 patient with pre B immunophenotype  Age group 6 months-16 years

8. CD19/CD10/CD34 CD19/CD10/CD45 or\and CD19/CD34/CD45 50 pt 1.Syto16/CD10/CD45/CD19 17pt 2. CD20/CD10/CD34/CD19 3 CD10/CD58/CD34/CD19

9.  31 patients  MRD < 0,1% – 19,4% ( 6 of 31)  MRD <0,1-10% – у 74 % (23 of 31)  MRD ≥10,0% – у 6,6% (2 of 31);

10.  30 patients  MRD <0,1-10% – у 86,6% (26 of 30)  MRD ≥10,0% – у13,4% (4 of 30) ;

11.  6 patients  MRD ≥10,0% - 100% (6 of 6)

12. Risk Group Morphological screening + MRD STANDARD-RISK GROUP (SR) 46,3% (31 )43.3% ( 29) INTERMEDIATE-RISK GROUP (IR) 44.8% (30)38.8%(26) HIGH-RISK GROUP (HR) 8.9% (6)17.9%(12)

13.  We can use MRD as independent prognostic factor in childhood  We can use MRD as tool for risk-group classification during front-line therapy  We can use MRD for adjust treatment intensity.

14. Thanks for you attention.