Absence of prognostic impact of CD13 and/or CD33 antigen expression in adult acute lymphoblastic leukemia. Results of the GIMEMA ALL 0496 trial

Background and Objectives The prognostic value of myeloid antigen (MyAg) expression in adult acute lymphoblastic leukemia (ALL) is still controversial. The aim of this study was to correlate the expression of MyAg with clinical, hematologic and biological parameters, and to analyze the impact on response to treatment and prognosis in a large series of adult ALL uniformly characterized and treated. Design and Methods We analyzed the expression of the MyAg CD13 and/or CD33 in a cohort of 377 adult patients with de novo ALL enrolled and treated in the GIMEMA ALL 0496 protocol. Results MyAg expression was documented in 35% of the 377 adult ALL cases analyzed. MyAg were significantly more frequently associated with B-lineage ALL (38%) than with T-ALL (24%) (p=0.02). No difference was found with regard to clinical features at presentation; a difference was found only for white cell count (p=0.03), percentage of peripheral blasts (p=0.004) and platelet count (p=0.004). No difference was observed in the expression of MyAg between patients with normal or abnormal cytogenetics or between those with high-risk (BCR-ABL+, ALL1-AF4+, E2A-PBX1+) or low-risk B-lineage ALL. We failed to observe any difference between MyAg-positive and MyAg-negative cases in terms of achievement of complete remission, disease-free survival and overall survival at 5 years. Interpretation and Conclusions Our data indicate that ALL MyAg expression in adults with ALL is not associated with adverse presenting clinical and biological features, and that response to treatment and prognosis is comparable in MyAg-positive and MyAg-negative ALL patients with regards to both complete remission rate and overall survival. We suppose that these result are due to more intensive treatment modalities adopted in the GIMEMA ALL 0496 protocol.