Abstract 4616

Chronic lymphocytic leukemia (CLL) is an indolent lymphoma with largely heterogeneous clinical course. Identifying patients which benefit from early therapy is one of the most important issues in the management of CLL. Besides patient-specific characteristics and applicability of different treatment approaches the decision on therapy is based on conventional prognostic parameters as well as on chromosomal aberrations, IgVH mutational status and expression of ZAP-70, which all have been shown to be independently associated with outcome. The expression of CD8 has been rarely observed in CLL and its prognostic impact is unclear yet. In order to clarify the frequency of CD8 expression, its correlation to established prognostic parameters as well as its prognostic impact we analyzed a total of 5,523 patients with CLL by multiparameter flow cytometry including the expression of CD8 between August 2005 and August 2010. Fluorescence in situ hybridization (FISH) applying a standard set of probes for the detection of del(6q), del(11q22.3) (ATM), trisomy 12, del(13q14) (D13S25, D13S319), and del(17p13) (TP53) was performed in 3,407 patients. IGHV mutational status was determined and evaluable in 2,845 patients. Clinical follow-up data was available in 1,021 patients (median follow-up: 21.3 months). 61 patients (1.1%) showed an expression of CD8 (antibody clone B9.11, Immunotech, France) as compared to isotype used as negative control. CD8+ vs. CD8- cases did not differ in age (mean±SD: 70.3±9.7 vs. 68.3±10.4 years, n.s.) and the male/female ratio was 1.11 vs. 1.61 (n.s.). There were no significant differences in WBC count (mean±SD, 31.7±33.9 vs. 36.1±53.1 × 10e9/l) and hemoglobin level (Hb, mean±SD, 13.6±2.0 vs. 13.2±2.1 g/dl), while platelet counts were higher in CD8+ vs. CD8- cases (229±72 vs. 194±99 × 10e9/l, p=0.021). In CD8+ vs. CD8- cases chromosomal aberrations were detected by FISH analysis with the following frequencies: del(6q), 5.9% vs. 3.1%, n.s.; del(11q22.3), 17.1% vs. 10.7% (n.s.); trisomy 12, 20.0% vs. 14.5% (n.s.); del(13q14), 66.7% vs. 59.8% (n.s.); del(13q14) as sole chromosomal aberration, 41.2% vs. 45.5% (n.s.); del(17q13), 2.9% vs. 5.7% (n.s.). The IGHV status was mutated in 79.3% vs. 60.4% (p=0.054) in CD8+ vs. CD8- cases. Patients with CD8 expression had a significantly shorter time to therapy (TTT) as compared to CD8- patients (median TTT, 12.0 vs. 77.1 months, p=0.008). The following parameters showed a significant relation to a shorter TTT in univariate Cox analyses: CD8 positivity, p=0.011, relative risk (RR)=2.87; higher WBC count, p=0.008, RR=1.01 per 10 × 10e9 increase; del(11q22.3), p<0.001, RR=1.97; del(17p13), p=0.005, RR=1.72; higher % of CLL cells with ZAP-70 expression (antibody clone SBZAP, Immunotech, France), p=0.011, RR=1.04 per 10% increase. Parameters significantly related to a longer TTT in univariate Cox analyses were: higher Hb level, p<0.001, RR=0.86 per 1 g/dl; higher platelet count, p=0.021, RR=0.98 per 10 × 10e9 increase; and del(13q14) as sole chromosomal aberration, p<0.001, RR=0.58. Multivariate analysis identified two parameters to be independently related to a shorter TTT: higher ZAP-70 expression (p=0.002) and CD8 positivity (p=0.036), while a higher Hb level (p<0.001) and del(13q14) as sole chromosomal aberration (p=0.011) were identified to be independently related to a longer TTT. This data supports the further evaluation of the prognostic impact of CD8 expression in CLL in order to define its role in identifying the most appropriate timepoint for therapy and the most appropriate treatment modality for patients with CLL.

Disclosures:

Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Schnittger:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

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Asterisk with author names denotes non-ASH members.