title: 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.
abstract: BACKGROUND
  Expression of CD56 has been associated with poor prognosis in acute myeloid leukemia and aggressive lymphoma.
  
  
  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.
authors.affiliation: Charité Campus Benjamin Franklin, Medizinische Klinik III, Berlin. lars.fischer@charite.de
authors.forename: Lars
authors.initials: L
authors.lastname: Fischer
authors.forename: Nicola
authors.initials: N
authors.lastname: Gökbuget
authors.forename: Stefan
authors.initials: S
authors.lastname: Schwartz
authors.forename: Thomas
authors.initials: T
authors.lastname: Burmeister
authors.forename: Harald
authors.initials: H
authors.lastname: Rieder
authors.forename: Monika
authors.initials: M
authors.lastname: Brüggemann
authors.forename: Dieter
authors.initials: D
authors.lastname: Hoelzer
authors.forename: Eckhard
authors.initials: E
authors.lastname: Thiel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019002:CD56 Antigen; D002986:Clinical Trials as Topic; D019008:Drug Resistance, Neoplasm; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D054218:Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy; D011379:Prognosis; D012074:Remission Induction / Q000379:methods; D016019:Survival Analysis; D055815:Young Adult
chemical_list: D019002:CD56 Antigen