The need to study the significance of minimal residual disease (MRD) at the induction therapy in patients with acute lymphoblastic leukemia (ALL) is beyond doubt. This has been confirmed by many years of work by many research groups. The role of MRD in the late stages of treatment and the impact of these values on patients survival requires research and discussion.

To evaluate the influence of MRD-status in post-induction period on survival in patients with acute lymphoblastic leukemia.

From 2010 to 2022, 135 patients with primary B-ALL enrolled in ALL-IC BFM 2009 protocol. Median age was 5.4 year (range 1-17). Male was 62 (49,5%) and female 73 (54,1%). The diagnosis was based on WHO 2016 criteria. Stratification on prognostic risk groups was carried out according to protocol criteria. Prednisone response evaluated at day 8 of treatment. The 15th, 33th, and 78th (as post-induction) day response was assessed by bone marrow cytology and level of MRD by flow cytometry.

5y-overall survival (OS) for patients with MRD-negative status on day 15 was 94,4±5,4% and 87,0±3,4% for MRD-positive (p=0,5). On day 33 patients with MRD-negative status achieved 5y-OS in 86,7±5,8% and 89,6±3,5% for MRD-positive (p=0,6).5y-OS for patients with MRD-negative status on day 78 was 90.8±4.0%, MRD-positive - 90,4+6.5%. DFS for MRD-negative status was 88.5±4.5%, for MRD-positive - 66.3±11.8% (p=0,1). EFS for MRD-negative patients was 87.2±4,6% and for MRD-positive 66.3±11.8% (p=0,09).

We have found a tendency between MRD status on day 78 and the frequency of relapses in patients. At the moment, there are no reliable data on the effect of post-induction MRD status on survival. The assessment of MRD in the post-induction period has prognostic prospects and requires further study.