Prognostic significance of CD38 and CD20 expression as assessed by quantitative flow cytometry in chronic lymphocytic leukaemia

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Abstract
Summary.CD38 expression on chronic lymphocytic leukaemia (CLL) cells is a poor prognostic factor, however, methods for measuring this vary. The QuantiBRITETMflow cytometry (FC) system yields an absolute antigen expression value (antibodies bound/cell, ABC) and may be useful in standardizing CD38 expression analysis. We evaluated cryopreserved pretreatment CLL cells for CD20 ABC, CD38 ABC, and percentage of CD38+B cells from 131 patients requiring therapy. The 92 patients (70%) with ≥ 100 CD38 ABC had worse overall survival (OS; 34% at 5 years) compared with those with < 100 CD38 ABC (70% at 5 years, mortality hazard ratio 2·30, 95% confidence interval 1·28–4·12; two‐tailedP = 0·003). Among the 64 patients with < 30% CD38+cells, OS of the 25 with ≥ 100 ABC was worse than that of the 39 with < 100 ABC (P = 0·018). OS of patients with < 30% CD38+cells and ≥ 100 ABC was actually similar to that of patients with ≥ 30% CD38+cells.BrightCD20 expression (≥ 20 000 ABC) was not associated with a worse OS (P = 0·10). The presence of ≥ 100 CD38 ABC in CLL patients requiring therapy is an unfavourable prognostic factor for OS and quantitative FC may be superior to percentage CD38+cell assessment. Prospective trials are required to determine more precisely the prognostic significance of absolute expression levels in fresh CLL cells.

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