[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 markers	CD34	29	17.24% (5/29)
	TdT	29	3.45% (1/29)
	CD10	29	10.34% (3/29)
	CD20	29	17.24% (5/29)
	CD22	19	15.79% (3/19)
	cIgM	18	33.33% (6/18)
Pan-B cell markers	CD19	29	0% (0/29)
	cCD79a	10	0% (0/10)
T-cell markers	CD2	29	0% (0/29)
	CD7	29	3.45% (1/29)
Myeloid markers	CD13	29	17.24% (5/29)
	CD33	29	20.69% (6/29)
Other marker	HLA-DR	29	0% (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