In chronic lymphocytic leukemia (CLL) the level of minimal residual disease (MRD) after therapy is an independent predictor of outcome. Given the increasing number of new agents being explored for CLL therapy, using MRD as a surrogate could greatly reduce the time necessary to assess their efficacy. In this European Research Initiative on CLL (ERIC) project we have identified and validated a flow-cytometric approach to reliably quantitate CLL cells to the level of 0.0010% (10(-5)). The assay comprises a core panel of six markers (i.e. CD19, CD20, CD5, CD43, CD79b and CD81) with a component specification independent of instrument and reagents, which can be locally re-validated using normal peripheral blood. This method is directly comparable to previous ERIC-designed assays and also provides a backbone for investigation of new markers. A parallel analysis of high-throughput sequencing using the ClonoSEQ assay showed good concordance with flow cytometry results at the 0.010% (10(-4)) level, the MRD threshold defined in the 2008 International Workshop on CLL guidelines, but it also provides good linearity to a detection limit of 1 in a million (10(-6)). The combination of both technologies would permit a highly sensitive approach to MRD detection while providing a reproducible and broadly accessible method to quantify residual disease and optimize treatment in CLL.

3rd Medical Department Paracelsus Medical University Salzburg Austria

Adaptive Biotechnologies Seattle WA USA

Department of Haematology Royal North Shore Hospital Sydney Australia

Department of Hematology Academic Medical Centre Amsterdam Netherlands

Department of Internal Medicine Hematology and Oncology University Hospital Brno and CEITEC Masaryk University Brno Czech Republic

Divisions of Hematology and Hematopathology Mayo Clinic Rochester MN USA

Experimental and Clinical Cell Therapy Institute Spinal Cord and Tissue Regeneration Center Paracelsus Medical University Salzburg Austria

General University Hospital Prague Czech Republic

Hematology and Flow Cytometry Laverty Pathology Sydney Australia

HMDS St James's Institute of Oncology Leeds UK

Hôpital Avicenne Assistance Publique Hôpitaux de Paris Bobigny France

Hospital Clínic IDIBAPS Barcelona Spain

Hospital de la Santa Creu i Sant Pau Barcelona Spain

Hospital Universitari Vall d'Hebron Barcelona Spain

Institute of Hematology and Blood Transfusion University Hospital Prague Prague Czech Republic

IRCCS San Raffaele Scientific Institute Milano Italy

Leeds Institute of Cancer and Pathology University of Leeds Leeds UK

MD Anderson Cancer Center Houston TX USA

Moores Cancer Center University of California San Diego La Jolla CA USA

National Cancer Institute National Institutes of Health Bethesda MD USA

Ohio State University Medical Center Columbus OH USA

Peter MacCallum Cancer Centre Melbourne Australia

Royal Liverpool and Broadgreen University Hospitals NHS Trust Liverpool UK

St James Hospital Dublin Ireland

Un1iversity of Pittsburgh Pittsburgh PA USA

Università Vita Salute San Raffaele Milan Italy

University Hospital Cologne Germany

University Hospital Geneva Geneva Switzerland

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Realizing precision medicine in chronic lymphocytic leukemia: Remaining challenges and potential opportunities

Reproducible diagnosis of chronic lymphocytic leukemia by flow cytometry: An European Research Initiative on CLL (ERIC) & European Society for Clinical Cell Analysis (ESCCA) Harmonisation project

Next-generation sequencing in chronic lymphocytic leukemia: recent findings and new horizons