Detection of minimal residual disease (MRD) by flow cytometry in children with acute lymphoblastic leukemia (ALL)
Margarita G. Bozhieva, Ludmila Y. Grivtsova, Alexander V. Popa, Irina N. Serebryakova, Irina E. Gavrilova, Boris V. Kurdyukov, Rono S. Ravshanova, Georgiy L. Mentkevich, Nikolay N. Tupitsyn
Pediatric Oncology and Hematology Research Institute, N. N. Blokhin RCRC RAMS, Moscow, Russia
The initial response of leukemia cells to treatment has consistently been shown to be a reliable prognostic indicator, and its evaluation has been significantly enhanced by methods that allow detection of submicroscopic levels of leukemia.
From January 2007 to April 2009, 45 patients with newly-diagnosed ALL were enrolled in ALL-IC BFM 2002 studies at our institution and had residual disease studies by flow cytometry on day 15 and day 33 of treatment. Of the 45 patients, 37 patients (82.2%) had a BCP-ALL and 8 had T-ALL (17.8%). Analyses were performed on a FACScan (Becton Dickinson). We used several standardized antibody combinations to screen ALL samples at diagnosis for leukemia-associated aberrations as well as to investigate BM.
In 40 samples (88.9%) on day 15 we identified at least 0.01% leukemic cells (0.01% – <0.1% in 12 (26.7%), 0.1% – <1% in 16 (35.6%), and ≥ 1% in 12 (26.7%). Of the 45 bone marrow samples studied by flow cytometry on day 15 of remission–induction therapy, 11 (24.4%) had leukemic lymphoblasts identifiable by morphologic analysis. In all the 11 morphologically positive samples, at least 0.1% cells expressing leukemia-specific immunophenotypes were detected by flow cytometry (median 17.2%, range 0.37% to 82.2%). Among the 34 (75.6%) samples without leukemic lymphoblasts recognizable by their morphologic features, 29 (64.5%) had detectable cells expressing leukemia-associated immunophenotypes (median 1.4%, range 0.01% to 25%).
The proportion of samples that were MRD+ was high on day 15 and decreased to 59.6% on day 33. Children with ALL who achieved an early clearance of leukemic cells had an excellent outcome.
acute lymphoblastic leukemia, children, minimal residual disease, flow cytometry