Chronic lymphocytic leukemia cells can be identified at levels as low as 0.0010% with a newly developed and validated single-tube assay, Dr. Andy C. Rawstro of St. James’s Institute of Oncology, Leeds, England, and his colleagues said in a European Research Initiative on CLL (ERIC) project report in Leukemia.
The high-throughput sequencing assay consists of a core panel of six markers – CD19, CD20, CD5, CD43, CD79b and CD81 – with a component specification independent of instrument and reagents. The new assay eliminates the need to distribute the blood sample across multiple tubes, which can impair sensitivity in cases with poor cellularity. The assay can be locally revalidated using normal peripheral blood and can be used to investigate new markers.
The new assay was validated in a multicenter study of 128 samples from 108 patients with CLL or monoclonal B-cell lymphocytosis, studied either at diagnosis or after FCR-based (fludarabine, cyclophosphamide, rituximab) treatment and compared with peripheral blood samples from healthy young women. In a parallel analysis, the assay compared with flow cytometry results at the 0.010% level, the minimal residual disease threshold defined in the 2008 International Workshop on CLL guidelines. The new assay, however, also was able to detect disease at the 0.0010% (one CLL cell in 1 million leukocytes) level.
The ability to detect disease below the levels that can be assessed by flow cytometry may prove to be a valuable resource to improve quantification of minimal residual disease and evaluate treatment response in CLL. Using minimal residual disease as a surrogate measure for treatment effectiveness would avoid the need for prolonged observation times in assessing new therapies, the researchers said (Leukemia 2016;30:929-36).
Dr. Rawstro disclosed receiving honoraria from Celgene, Abbvie, Gilead, Roche, and GSK. He receives royalty payments from BD Biosciences (Intrasure reagent) and study reagents. He is a consultant for Gilead and Biogen Idec.
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