Clinical significance of CD56 expression in patients with acute promyelocytic leukemia treated with all-trans retinoic acid and anthracycline-based regimens

<jats:title>Abstract</jats:title> <jats:p>The expression of CD56 antigen in acute promyelocytic leukemia (APL) blasts has been associated with short remission duration and extramedullary relapse. We investigated the clinical significance of CD56 expression in a large series of patients with APL treated with all-trans retinoic acid and anthracycline-based regimens. Between 1996 and 2009, 651 APL patients with available data on CD56 expression were included in 3 subsequent trials (PETHEMA LPA96 and LPA99 and PETHEMA/HOVON LPA2005). Seventy-two patients (11%) were CD56+ (expression of CD56 in ≥ 20% leukemic promyelocytes). CD56+ APL was significantly associated with high white blood cell counts; low albumin levels; BCR3 isoform; and the coexpression of CD2, CD34, CD7, HLA-DR, CD15, and CD117 antigens. For CD56+ APL, the 5-year relapse rate was 22%, compared with a 10% relapse rate for CD56− APL (P = .006). In the multivariate analysis, CD56 expression retained the statistical significance together with the relapse-risk score. CD56+ APL also showed a greater risk of extramedullary relapse (P < .001). In summary, CD56 expression is associated with the coexpression of immaturity-associated and T-cell antigens and is an independent adverse prognostic factor for relapse in patients with APL treated with all-trans-retinoic acid plus idarubicin–derived regimens. This marker may be considered for implementing risk-adapted therapeutic strategies in APL. The LPA2005 trial is registered at http://www.clinicaltrials.gov as NCT00408278.</jats:p>