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.

BACKGROUND: The WHO and iwCLL diagnostic criteria for CLL rely on morphology and immunophenotype based on the co-expression of CD19/CD5/CD23 on B-cells with weak CD20 and monoclonal sIg expression. These diagnostic criteria are likely to persist in the near future because there is no specific diagnostic molecular abnormality for CLL. The current criteria have some limitations affecting reproducibility, particularly flexibility in marker expression with many centres using a scoring system that permits absence of CD5 or CD23. Potentially informative new markers have been identified but there is no consensus yet on which should be routinely assessed. AIM: To identify reproducible criteria and to achieve a consensus on markers recommended for the diagnosis of CLL METHODS: ERIC/ESCCA members were invited to classify 35 flow-cytometry markers as being required or recommended for the diagnosis of CLL. Consensus was considered to be achieved if >75% of participants agreed on the marker classification. A diagnostic panel was identified by the steering committee and characteristics of component markers that could be reproducibly validated within an individual laboratory were identified. The proposed panel was assessed in 13 different centres. RESULTS: Responses were received from 154 members (100 laboratory staff, 14 clinicians and 36 from both laboratory and clinic) with a diagnostic workload >20 cases per week in 23/154 (15%), 5-20 in 82/154 (53%) and <5 cases per week in 49/154 (32%). The consensus minimum diagnostic panel should include : CD19, CD5, CD20, CD23, Kappa and Lambda. Participants recommended the following markers: CD38, CD45, CD79b, CD10, CD22, CD43, CD200, and FMC7. A minimum and recommended panel with reproducible criteria for component reagents were determined and the criteria were applied to 10,876 cases diagnosed with a B-LPD, of which 8120 were CD5+ B-LPD. Out of 5947 sent as a primary referrals for diagnosis, 4493 (75.6%) met the proposed diagnostic criteria for CLL, 821 (13.8%) did not and had a clear alternative diagnosis (e.g. MCL) and 633 (10.6%) would not be readily classified by flow cytometry if the proposed criteria were applied. Out of 2173 cases previously diagnosed as CLL at another centre, 2028 (93.3%) met the proposed diagnostic criteria, 19 (0.9%) had a clear alternative diagnosis while 126 (5.8%) did not meet the flow-cytometry criteria. CONCLUSIONS: We present flow-cytometry criteria for the diagnosis of CLL largely consistent with current practice. In addition, reproducible definitions of the required expression pattern and performance characteristics of reagents are provided. Prospective evaluation of the proposed criteria as well as a parallel project to facilitate definitive diagnosis of CD5+ B-LPD cases that do not meet the proposed criteria are underway. Figure 1. required and recommended markers for use in the diagnosis of CLL with reagent specification based on expression patterns in normal peripheral blood. Figure 1. required and recommended markers for use in the diagnosis of CLL with reagent specification based on expression patterns in normal peripheral blood. ‡ Weak expression = median fluorescence intensity at least 20% lower than median for normal peripheral blood B-cells, reference range determined within each laboratory, based on ICSH/ISLH/CLIA guidelines for reproducibility *consensus, not specifically validated Disclosures Rawstron: Abbvie: Honoraria; Pharmacyclics: Research Funding; Celgene: Honoraria; Roche: Honoraria; BD Biosciences: Patents & Royalties; Gilead: Honoraria, Research Funding. Cuneo:Roche: Speakers Bureau; Gilead: Speakers Bureau; Jannsen: Speakers Bureau; Celgene: Speakers Bureau; Novartis: Speakers Bureau. Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Trneny:Celgene: Consultancy, Honoraria, Other: Travel, accommodations, expenses, Research Funding. Mulligan:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Speakers Bureau; Roche: Consultancy, Honoraria, Research Funding, Speakers Bureau; Sanofi Aventis: Research Funding. Hillmen:Celgene: Research Funding; Gilead: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; GSK: Consultancy, Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Roche: Consultancy, Honoraria, Research Funding. Hallek:Gilead: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding; Boehringher Ingelheim: Honoraria, Other: Speakers Bureau and/or Advisory Boards; Janssen: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding; Mundipharma: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding; Celgene: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding; Roche: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding; AbbVie: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding; Pharmacyclics: Honoraria, Other: Speakers Bureau and/or Advisory Boards, Research Funding. Ghia:AbbVie: Consultancy; Janssen: Consultancy; Roche: Consultancy, Research Funding; Adaptive: Consultancy; Gilead: Consultancy, Research Funding, Speakers Bureau; GSK: Research Funding; Acerta Pharma BV: Research Funding; Pharmacyclics: Consultancy.

The diagnostic criteria for CLL rely on morphology and immunophenotype. Current approaches have limitations affecting reproducibility and there is no consensus on the role of new markers. The aim of this project was to identify reproducible criteria and consensus on markers recommended for the diagnosis of CLL. ERIC/ESCCA members classified 14 of 35 potential markers as “required” or “recommended” for CLL diagnosis, consensus being defined as >75% and >50% agreement, respectively. An approach to validate “required” markers using normal peripheral blood was developed. Responses were received from 150 participants with a diagnostic workload >20 CLL cases per week in 23/150 (15%), 5–20 in 82/150 (55%), and <5 cases per week in 45/150 (30%). The consensus for “required” diagnostic markers included: CD19, CD5, CD20, CD23, Kappa, and Lambda. “Recommended” markers potentially useful for differential diagnosis were: CD43, CD79b, CD81, CD200, CD10, and ROR1. Reproducible criteria for component reagents were assessed retrospectively in 14,643 cases from 13 different centers and showed >97% concordance with current approaches. A pilot study to validate staining quality was completed in 11 centers. Markers considered as “required” for the diagnosis of CLL by the participants in this study (CD19, CD5, CD20, CD23, Kappa, and Lambda) are consistent with current diagnostic criteria and practice. Importantly, a reproducible approach to validate and apply these markers in individual laboratories has been identified. Finally, a consensus “recommended” panel of markers to refine diagnosis in borderline cases (CD43, CD79b, CD81, CD200, CD10, and ROR1) has been defined and will be prospectively evaluated. © 2017 International Clinical Cytometry Society

Summary Chronic lymphocytic leukaemia (CLL) is associated with immunocompromise and high risk of severe COVID‐19 disease and mortality. Monoclonal B‐cell lymphocytosis (MBL) patients also have immune impairment. We evaluated humoural and cellular immune responses in 181 patients with CLL (160) and MBL (21) to correlate failed seroconversion [<50 AU/ml SARS‐CoV‐2 II IgG assay, antibody to spike protein; Abbott Diagnostics)] following each of two vaccine doses with clinical and laboratory parameters. Following first and second doses, 79.2% then 45% of CLL, and 50% then 9.5% of MBL patients respectively remained seronegative. There was significant association between post dose two antibody level with pre‐vaccination reduced IgM (p < 0.0001), IgG2 (p < 0.035), and IgG3 (p < 0.046), and CLL therapy within 12 months (p < 0.001) in univariate analysis. By multivariate analysis, reduced IgM (p < 0.0002) and active therapy (p < 0.0002) retained significance. Anti‐spike protein levels varied widely and were lower in CLL than MBL patients, and both lower than in normal donors. Neutralisation activity showed anti‐spike levels <1000 AU/ml were usually negative for both an early viral clade and the contemporary Delta variant and 72.9% of CLL and 53.3% of MBL failed to reach levels ≥1000 AU/ml. In a representative sample, ~80% had normal T‐cell responses. Failed seroconversion occurred in 36.6% of treatment‐naïve patients, in 78.1% on therapy, and in 85.7% on ibrutinib.

Chronic lymphocytic leukemia (CLL) is associated with immunocompromise and high risk of severe COVID-19 disease and mortality. Monoclonal B-Lymphocytosis (MBL) patients also have immune impairment. We evaluated humoral and cellular immune responses in 181 patients with CLL (160) and MBL (21) to correlate failed seroconversion (<50AU/mL SARS-CoV-2 II IgG assay, antibody to spike protein, Abbott Diagnostics) following each of 2 vaccine doses with clinical and laboratory parameters. Following first and second doses, 79.2% then 45% of CLL, and 50% then 9.5% of MBL respectively remained seronegative, indicating 2 vaccine doses are crucial. There was significant association between post-dose 2 antibody level with pre-vaccination reduced IgM (p<0.0001), IgG2 (p<0.035), IgG3 (p<0.046), and CLL therapy within 12 months (p<0.001) in univariate analysis. By multivariate analysis, reduced IgM (p<0.0002) and active therapy (p<0.0002) retained significance. There was no significant correlation with age, gender, CLL duration, IgG, IgA or lymphocyte subsets. Anti-spike protein levels varied widely and were lower in CLL, than MBL, and both lower than normal donors. Neutralization activity showed anti-spike levels <1000AU/mL were usually negative for both an early viral clade and the contemporary Delta variant. There were 72.9% of CLL and 53.3% of MBL who failed to reach anti-spike levels >1000AU/mL. In a representative subset of 32 CLL patients, 80% had normal T-cell responses by IFNγ and IL-2 FluoroSpot assay. Failed seroconversion occurred in 36.6%% of treatment-naive patients, 52.9% treatment-naive with reduced IgM, 78.1% on therapy, and 85.7% on ibrutinib. Vaccination failure is very common in CLL, including early-stage disease.6 Key Novel FindingsComparison CLL vs MBL vs normal-45% of CLL and 9.5% of MBL fail to seroconvert with 2 doses of COVID-19 vaccineNeutralization assay-SARS CoV-2 IgG levels <1000 AU/mL rarely associated with neutralization activity.COVID-19-specific T-cell function by FluoroSpot IFN-g and IL-2 productionIgG, A, M class and IgG subclass: correlations by univariate and multivariate analysis-IgM (OR 7.29 p<0.0001), IgG2 and IgG3 subclass univariate significanceCorrelation with therapy – ICT, targeted therapies, and those on Ig replacementHigh risk of vaccination failure for all CLL, including early-stage disease, and MBLKey PointsCLL and MBL show significantly impaired anti-spike antibody, viral neutralization, with cellular immune response to COVID-19 vaccinationFailure to seroconvert is associated with low IgM, IgG2, IgG3, and recent therapy; many CLL and MBL patients remain COVID-19 vulnerable