CD56 expression in acute promyelocytic leukemia: A possible indicator of poor treatment outcome?

Purpose: Blast expression of CD56 is frequent in patients with t(8;21)(q22; q22) acute myeloid leukemia and is associated with an inferior outcome. The expression of CD56 has rarely been reported in acute promyelocytic leukemi a (APL) and has nat been clinically characterized. Therefore, we examined t he prognostic significance of CD56 expression in APL, Patients and Methods: We identified all reported cases of CD56(+) APL in th e medical literature and collected clinical, biologic, and therapeutic deta ils. Results: Data were obtained for 12 patients with CD56(+) APL (> 20% blast e xpression of CD56), including four cases from a single institution with a t otal of: 42 APL patients. All of the CD56(+) APL patients had documented cy togenetic presence of t(15;17), and of the nine reported isotypes, eight (8 9%) were S-isoform. Only six CD56(+) patients (50%) attained complete remis sion (CR); the other six individuals died within 35 days of presentation. O f the six patients who attained a CR, three (50%) relapsed at 111, 121, and 155 weeks, whereas three remained in continuous CR at 19, 90, and 109 week s. Comparison of the control CD56(-) to CD56(+) APL patients demonstrated t hat the latter group had a significantly lower fibrinogen level (P = .007), and among patients far whom data were available, there was a higher freque ncy of the S-isoform (P = .006). Additionally, the CR rate (50% v 84%, P = .025) and overall median survival (5 v 232 weeks; P = .019)were significant ly inferior for CD56(+) APL patients. Conclusion: CD56(+) acute promyelocytic leukemia is infrequent, seems to oc cur more frequently with the S-isoform subtype, and may be associated with a lower CR rate and inferior overall survival. J Clin Oncol 17:293-297. (C) 1999 by American Society of Clinical Oncology.