[1381] Comparison of B-Cell Lineage and Prognostic Markers before and after Therapy with Rituximab-Containing Regimen in Diffuse Large B-Cell Lymphoma (DLBCL) and Chronic Lymphocytic Leukemia (CLL)

BM Mahon, Y Chen. Northwestern Memorial Hospital, Chicago, IL

Background: It is well known that in a significant number of patients with B-cell lymphoma, the neoplastic B-cells become CD20- after therapy with rituximab; this has been observed with both immunohistochemistry (IHC) and flow cytometry (FC). However, changes in the staining of other lineage and prognostic markers are less well recognized. In this study, we examined a series of B-cell lineage and prognostic markers in pre- and after-treatment samples of DLBCL and CLL.
Design: Patients with a diagnosis of DLBCL treated with rituximab and with both positive pre- and post-therapy biopsies in our institution were searched from the database. CLL cases negative for CD20 by FC with a history of rituximab therapy were also searched. For DLBCL, IHC for B-cell lineage markers, CD20, CD79a, PAX-5, OCT-2 and BOB.1, and prognostic markers, CD10, BCL-6, BCL-2 and MUM-1, were performed. For CLL, IHC for CD20 and prognostic marker, Zap-70, were performed.
Results: A total of 58 samples from 27 patients were retrieved including 21 samples from 9 patients with DLBCL and 37 samples from 18 patients with CLL. In DLBCL, changes in the staining of B-cell lineage markers in post-therapy biopsies were observed in 13 of 21 samples from 5 of 9 (55%) patients. Changes were seen in CD20, CD79a, PAX-5, BCL-2, BCL-6, BOB.1, and CD10 expression. All 18 CLL patients negative for CD20 by FC in post-therapy biopsies were CD20+ before therapy by FC and IHC. IHC for CD20 in post-therapy biopsies showed that 13 of 19 samples from 12 of 18 (66%) patients were CD20+. IHC for Zap-70 was positive in neoplastic cells in 24 of 36 samples from 11 of 17 (65%) patients. FC results for Zap-70 were available in 15 samples and Zap-70 status determined by IHC correlated with FC analysis in 13 samples (83%).
Conclusions: 1. Chemotherapy regimens containing rituximab may not only affect the CD20 staining, but also other B-cell lineage and prognostic markers. It should be interpreted with caution in patients with residual/recurrent diseases after therapy. 2. CD20 is positive by IHC in a significant number of post-therapy CLL patients who were CD20- by FC. IHC may provide additional information regarding CD20 status in these patients for clinical therapeutic decisions. 3. Zap-70 does not change during the course of treatment. The Zap-70 status determined by IHC strongly correlates with the previously established objective FC analysis in this study.
Category: Hematopathology

Wednesday, March 24, 2010 9:30 AM

Poster Session V # 186, Wednesday Morning


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