Expression of myeloid markers lacks prognostic impact in children treated for acute lymphoblastic leukemia: italian experience in AIEOP-ALL 88-91 Studies

The importance of coexpression of myeloid antigens in childhood acute lymphoblastic leukemia (ALL) has long been debated; results are conflicting. We studied children with ALL treated at Italian Association for Pediatric Hematology-Oncology (AIEOP) institutions over 6 years with Berlin-Frankfurt-Muenster (BFM)-based protocols and have analyzed the incidence of coexpression of six MyAg (CD11b, CD13, CD14, CD15, CD33, CD65w) to determine its prognostic impact. Criteria for MyAg coexpression (MyAg+ALL) included positivity to one or more MyAg on at least 20% of blasts and confirmation of coexpression at double-fluorescence analysis. A total of 291 of 908 cases were MyAg+ALL (32%). Incidence was similar in B-ALL and T-ALL; among common, pre-B, and pre-pre-B-ALL. CD13 and CD33 were most common. Patients with MyAg+ALL had presenting features similar to MyAg-ALL. They entered standard or intermediate risk protocols more frequently and had better prednisone response, but similar complete remission rates. Six-year event-free survival (EFS) was 69.0% in 291 MyAg+ALL cases and 65.3% in 617 MyAg-ALL cases, without significant difference. Cases expressing two or more MyAg presented similar clinical features and treatment response. MyAg+ALL had worse EFS only in infants (0% v 47%) (P = .01). Therefore, in this series of homogeneously diagnosed and treated ALL, coexpression of MyAg was not associated with prognostic significance, without relevance for clinical purposes or for patient stratification, except for infants