[1298] Characterization of Immunophenotype Changes in Precursor B-Lymphoblastic Leukemia of Childhood during the Course of Leukemia Progression

F Castro-Silva, J Shao, A McGranahan, X Liang. The Children's Hospital, Aurora; University of Colorado Denver, Aurora

Background: Precursor B-lymphoblastic leukemia (LL) is the most common leukemia in childhood. Although there has been a significant improvement in the treatment of LL, patients with LL relapse remain more difficult to treat, convey a worse prognosis, and require different therapeutic approaches. Immunophenotypic characterization not only plays an important role in diagnosis of LL but also provides important information for the selection of an effective therapy to treat patients with leukemia relapse. It is unclear if immunophenotype changes significantly and what the pattern of change is during the course of precursor B-LL progression. We examined immunophenotype in a series of precursor B-LL at time of diagnosis and subsequent relapses.
Design: 29 cases of precursor B-LL at The Children's Hospital, Colorado from 1998 to 2009 which had immunophenotype available at both diagnosis and relapses were evaluated. Immunophenotype was performed by flow cytometry. We evaluated the frequency of change (“+” to “-” or “-” to “+”) (“+” is defined as expression of a marker in ≥20% of blasts) in each marker between initial diagnosis and relapse, and also between subsequent relapses.
Results: Frequencies of immunophenotype change during the course of leukemia progression in precursor B-LL of childhood.

# of cases% of cases with antigen
expression change during the
leukemia progression
Maturation related markersCD342917.24% (5/29)
TdT293.45% (1/29)
CD102910.34% (3/29)
CD202917.24% (5/29)
CD221915.79% (3/19)
cIgM1833.33% (6/18)
Pan-B cell markersCD19290% (0/29)
cCD79a100% (0/10)
T-cell markersCD2290% (0/29)
CD7293.45% (1/29)
Myeloid markersCD132917.24% (5/29)
CD332920.69% (6/29)
Other markerHLA-DR290% (0/29)



Conclusions: (1) Expression of maturation-related markers (CD20, CD22, cIgM, CD34, and CD10) and myeloid markers is more unstable (changes in 10%-33% of cases) during the course of precursor B-LL progression in pediatric patients. These findings suggest that instability in blast maturation and/or myeloid antigen expression may partially be responsible for a more aggressive clinical behavior in precursor B-LL at relapse. (2) CD20, CD22, and CD33 should be included in both diagnostic and relapsed panels due to potential therapeutic choices for treating relapsed patients with Ritaximab (anti-CD20), Epratuzumab (anti-CD22), and Gemtuzumab (anti-CD33).
Category: Hematopathology

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 186, Tuesday Afternoon

 

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