Lineage Classification of Childhood Acute Lymphoblastic Leukemia according to the EGIL Recommendations: Results of the ALL-BFM 2000 Trial

Abstract

Flow cytometry immunophenotyping (FCM) is an undispensable tool for the diagnosis and for the treatment stratification of childhood acute lymphoblastic leukemia. The correlation of the EGIL-classification with prognostically relevant parameters like age, prednisone response and risk group is analyzed. Between March 2000 and June 2009 12 patients less than 1 year of age, 1 836 patients with 1 to less than 6 years, 620 patients with 6 to less than 10 years, 615 patients with 10 to less than 15 years and 275 patients with 15 to less than 19 years were analyzed with a comprehensive 4-color antibody panel and classified according to the EGIL recommendations. Bone marrow or peripheral blood mononuclear cells were isolated by ficoll gradient centrifugation, washed and stained with fluorochrome-conjugated antigen-specific monoclonal antibodies. Cell preparations were acquired and analyzed on a flow cytometer. Centralized FCM was performed for 2 775 patients (82.6%) with B-cell precursor acute lymphoblastic leukemia, 493 patients (14.7%) with T-cell acute lymphoblastic leukemia and 90 patients (2,7%) with biphenotypic acute leukemia. There was a slight overall predominance of male (56.1%) over female (43.9%) patients. Patients with B-cell precursor ALL had a slightly more favourable outcome with a 10 y pEFS of 78 ± 1.0%, compared to patients with a T-ALL or BAL (biphenotypic acute leukemia) phenotype with a 10 y pEFS of 74 ± 1.8% (n.s.) or 69 ± 9.0% (p<0.009), respectively. FCM according to the EGIL recommendations not only provides diagnostic lineage determination and subclassification but also enables an initial prognostic orientation before MRD (minimal residual disease)-based risk stratification becomes available.