CD11b Expression is an independent adverse prognostic factor in pediatric acute myeloid leukemia treated with allogeneic stem cell transplantation

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Background: The adhesion molecule CD11b, which associates with the beta2-integrin to form the Mac-1 complex, is expressed in monocytic leukemias as well as other myeloid leukemias. Its expression on the lekemic cells has been reported to correlate with more aggressive course in adult patients with AML. The clinical relevance of CD11b expression in pediatric AML is not known. More importantly, the clinical relevance of CD11b expression on pediatric AML when these patients are treated with allogeneic hematopoietic stem cell transplant (HSCT). We investigated whether HSCT can modify the expected adverse effects of CD11b expression in pediatric AML patients.
Methods: Immunophenotype data of 62 pediatric patients with AML, all treated with allogeneic HSCT, was reviewed. The expression of the CD11b on the blast population as determined by flow cytometry was correlated with clinical data and outcome. The median age of patients was 8 years (range: 8 months–14 years) and included 47 (76%) patients transplanted in their first complete remission (CR1). Fourty six (74%) of all patients had intermediate-risk cytogenetics and the remaining (26%) had adverse-risk cytogenetic abnormalities.
Results: Twenty five (40%) of all studied patients expressed CD11b on the surface of the blasts at diagnosis. Patients with CD11b expression had significantly shorter overall survival (P=0.038) with median survival of approximately 11 months while the median survival in the CD11b negative patients has not been reached. Similarly, CD11 positive patients had significantly shorter event free survival (EFS) (P=0.03). When we considered only patients treated with HSCT in CR1, the OS and EFS for the CD11b positive patients were both significantly shorter (P=0.04 and P=0.05, respectively). Multivariate analysis including CD11b expression and cytogenetic risk identified CD11b expression as an independent prognostic factor for survival and EFS, while cytogenetic-risk stratification became no longer a predictor.
Conclusion: Our data suggests that the expression of CD11b in pediatric AML is a significant independent poor prognostic factor and HSCT does not change this trend. Most of the CD11b positive patients die in their first year after HSCT and the management of these patients should be modified to address the biological basis of this subset of AML that expresses CD11b adhesion molecule.


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This work was published before the author joined Aga Khan University

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