CD56 expression in T-cell acute lymphoblastic leukemia is associated with non-thymic phenotype and resistance to induction therapy but no inferior survival after risk-adapted therapy

1 Charité Campus Benjamin Franklin, Medizinische Klinik III, Berlin 2 Johann Wolfgang Goethe-Universität, Medizinische Klinik III, Frankfurt/Main 3 Heinrich-Heine-Universität, Institut für Humangenetik und Anthropologie, Düsseldorf and 4 Universitätsklinikum Schleswig-Holstein, II. Medizinische Klinik und Poliklinik, Kiel, Germany Correspondence: Lars Fischer, MD, Charité Campus Benjamin Franklin, Medizinische Klinik III, Hindenburgdamm 30, 12200 Berlin, Germany. E-mail: lars.fischer{at}charite.de Background: Expression of CD56 has been associated with poor prognosis in acute myeloid leukemia and aggressive lymphoma. Design and Methods: We analyzed the impact of CD56 expression in a cohort of 452 newly diagnosed adult T-cell acute lymphoblastic leukemia (T-ALL) patients; clinical data were available for 306 patients. Treatment was according to the GMALL study protocols 06/99 and 07/03 stipulating stratification into standard (thymic T-ALL) and high risk (pre- and mature T-ALL) groups. Results: CD56 expression was detected in 63/452 (13.9%) patients. CD56 + T-ALL were predominantly of non-thymic (pre-T 35%, mature 41%) immunophenotypic subtypes, whereas 53% of the CD56 – cases were thymic T-ALL ( p =0.00002). CD13, CD33, CD34 and HLA-DR were significantly more frequently expressed. A clonal T-cell receptor rearrangement was detected in 22/23 CD56 + ALL. No major clinical differences were observed at presentation. Treatment of CD56 + ALL resulted in a lower rate of complete remissions (70% vs. 88%) ( p =0.001) and a higher rate of resistant disease (21% vs. 8%) ( p =0.004). CD56 expression had no significant influence on overall (48% vs. 59%) and disease free survival (67% vs. 57%) at three years. Conclusions: CD56 is expressed on a subset of adult T-ALL with distinct immunophenotypical features and higher resistance to therapy. Most CD56 + ALL were treated in the high-risk arm of the GMALL study protocols owing to their non-thymic phenotype. Thus after risk adapted treatment a prognostic impact of CD56 expression was not detectable. Key words: T-cell ALL, CD56, natural killer, immunophenotype. Related Article T-cell acute lymphoblastic leukemia Sabina Chiaretti, Robin Foà Haematologica 2009 94: 160-162. [Full Text] [PDF]