EXPRESSION OF THE NEURAL CELL-ADHESION MOLECULE-CD56 IS ASSOCIATED WITH SHORT REMISSION DURATION AND SURVIVAL IN ACUTE MYELOID-LEUKEMIA WITH T(8-21)(Q22-Q22)

Although acute myeloid leukemia (AML) with t(8;21) (q22;q22) is associ ated with a high complete remission (CR) rate and prolonged disease-fr ee survival, treatment outcome is not universally favorable. Identifyi ng factors that predict for treatment outcome might allow therapy to b e optimized based on risk. AML with t(8;21) has a distinctive immunoph enotype, characterized by expression of the myeloid and stem cell anti gens CD13, CD15, CD34, and HLADr, and frequent expression of the B-cel l antigen CD19 and the neural cell adhesion molecule CD56, a natural k iller cell/stem cell antigen. Because CD56 expression has been associa ted with both extramedullary leukemia and multidrug resistance, we sou ght to correlate CD56 expression with treatment outcome in AML with t( 8;21). Pretreatment leukemia cells from 29 adult de novo AML patients with t(8;21) treated on Cancer and Leukemia Group B (CALGB) protocols were immunophenotyped by multiparameter flow cytometry as part of a pr ospective immunophenotyping study of adult AML (CALGB 8361). CD56 was expressed in 16 cases (55%). There was no correlation between CD56 exp ression and age, sex, white blood cell count, granulocyte count, the p resence of additional cytogenetic abnormalities, or the presence of ex tramedullary disease at diagnosis. The CR rate to standard-dose cytara bine and daunorubicin was similar for cases with and without CD56 expr ession (88% v 92%; P = 1.0). Post-CR therapy included at least one cou rse of high-dose cytarabine in 24 of 26 patients who achieved CR; numb ers of courses administered were similar in cases with and without CD5 6 expression. Although post-CR therapy did not differ, CR duration was significantly shorter in cases with CD56 expression compared with tho se without (median, 8.7 months v not reached; P = .01), as was surviva l (median, 16.5 months v not reached; P = .008). We conclude that CD56 expression in AML with t(8;21) is associated with significantly short er CR duration and survival. Our results suggest that CD56 expression may be useful in stratifying therapy for this subtype of AML. (C) 1997 by The American Society of Hematology.