Monoclonal B-cell Lymphocytosis Research Articles

Abstract 5256: Incidence of squamous cell carcinoma (SCC) in a large screening cohort of monoclonal B-cell lymphocytosis (MBL)

Abstract MBL is a common pre-malignant condition characterized by circulating clonal B-cells with an absolute B-cell count <5x109/L and no lymphadenopathy, organomegaly, or cytopenias. MBL is the precursor to CLL. The incidence of cutaneous SCC in CLL is significantly higher compared to controls. The incidence of SCC in MBLs has not yet been determined. Study participants from the Mayo Clinic Biobank who had no prior history of hematologic malignancy, were 40 years or older, and were Olmsted County residents completed a health questionnaire and provided blood samples between 7/2009 and 12/2020. Stored peripheral blood mononuclear cells were screened for MBL using flow cytometry. We defined three MBL immunophenotypes: CLL-like MBL (CD5+, CD20dim), atypical MBL (CD5+, CD20+), and non-CLL-like MBL (CD5-, CD20+). MBL individuals were also classified by cell count into low-count MBL (LC-MBL) and high-count MBL (HC-MBL), with HC-MBL having a percent clonal B-cell count ≥85%. Data on newly diagnosed SCC was abstracted from the medical records, and prior history of skin cancer before sample collection was ascertained from patient questionnaires. Individuals were followed from sample date to the earliest of SCC, death, loss to follow-up, progression, or 12/31/2020. Cumulative SCC incidence was adjusted for competing risk of death. Cox regression was used to calculate hazard ratios (HR) and 95% confidence intervals (CIs) adjusted for age and sex. A total of 5,470 participants were screened for MBL and included 949 (17%) with LC-MBL, 63 (1%) with HC-MBL, and 4,458 (81%) controls (negative for MBL). Individuals with HC-MBL (median age 75 years) or LC-MBL (median age 73 years) were significantly older (P<0.001) than controls (median age 66 years). There were 41 (65%) males among HC-MBL, 447 (47%) among LC-MBL, and 1,551 (35%) among controls. Prior skin cancer history was highest among HC-MBLs (N=17, 27%) or LC-MBLs (N=236, 25%) compared to controls (N=767, 17%). After a median follow-up of 18 months (range 0-138), 154 of the 5,470 individuals were identified to have incident SCC following MBL screening. At least one SCC was observed in 3 individuals with HC-MBL, 33 individuals with LC-MBL, and 118 controls. The 5- and 10-year cumulative incidence of SCC in individuals with MBLs was 7% and 16%, respectively; control estimates were 4% and 8%, respectively. However, after adjusting for age and sex, we observed no evidence of an association between MBL and risk of incident SCC (HR=0.95, CI=0.65-1.40, P=0.80), nor when we stratified individuals by age or by sex (all P>0.05). In the largest MBL screening cohort to date, individuals with MBL do not have an increased risk of incident SCC compared to controls. In contrast to individuals with CLL, these individuals with screening MBL do not need increased dermatologic examination for skin cancer, which is important given the high prevalence of MBL (18% of the population above age 40). Citation Format: Ahmed Nadeem Ansari, Sara J. Achenbach, Sameer A. Parikh, Geffen Kleinstern, Aaron D. Norman, Kari G. Rabe, Connie E. Lesnick, Timothy G. Call, Janet E. Olson, James R. Cerhan, Neil E. Kay, Celine M. Vachon, Esteban Braggio, Curtis A. Hanson, Tait D. Shanafelt, Christian L. Baum, Susan L. Slager. Incidence of squamous cell carcinoma (SCC) in a large screening cohort of monoclonal B-cell lymphocytosis (MBL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5256.

Serum soluble CD23 levels are an independent predictor of time to first treatment in chronic lymphocytic leukemia.

Serum soluble CD23 (sCD23) levels have been acknowledged as a prognostic factor in patients with chronic lymphocytic leukemia (CLL), but their potential relevance has not been analyzed in recent times. We retrospectively studied 338 CLL, small lymphocytic lymphoma, or CLL-type monoclonal B-cell lymphocytosis patients from a single institution, with available sCD23 levels at diagnosis. Baseline features and outcomes were compared between patients with sCD23 ≤/>1000UI/L. The 140 patients (41%) who had sCD23>1000 UI/L showed adverse-risk clinical and biological characteristics. High sCD23 levels were predictive of a shorter time to first treatment (5-year probability of requiring treatment: 60 vs. 20%, p<0.0001; hazard ratio (HR)=1.72, p=0.003 in a multivariable model also including the CLL International Prognostic Index and the absolute lymphocyte count), and a poorer 5-year overall survival (70 vs. 82%, p=0.0009). These data suggest the potential of sCD23 to predict treatment-free survival and to shed light on mechanisms of activity and resistance to CD23-directed therapies.

A new diagnosis of monoclonal B-cell lymphocytosis with cytoplasmic inclusions in a patient with COVID-19.

A new diagnosis of monoclonal B-cell lymphocytosis with cytoplasmic inclusions in a patient with COVID-19.

Monoclonal B-cell lymphocytosis in the bone marrow: revisiting the criteria for chronic lymphocytic leukemia/small lymphocytic lymphoma

Monoclonal B-cell lymphocytosis is a clonal B-cell population in the peripheral blood (PB) of <5x10ˆ9/L without extramedullary (EM) disease, often with a chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) phenotype. The degree of bone marrow (BM) involvement is not currently a part of the diagnostic criteria for MBL or CLL/SLL, but CLL-type MBLs in BM can be seen in patients lacking PB lymphocytosis. Data are limited on the outcome of such cases. We assessed the clinicopathologic characteristics of isolated BM CLL-type MBL in patients who did not meet criteria for CLL/SLL. We evaluated BMs from 2006 to 2018 with CLL-like clonal B-cell populations in patients with a PB absolute lymphocyte count or monoclonal B-cell count of <5×109/L and without definite evidence of EM disease. We investigated the extent and pattern of marrow involvement, PB counts, flow cytometric data, genetics, concurrent hematopoietic diseases, and outcomes including progression and treatment. Thirty cases with BM MBL but <5x10E9/L PB monoclonal B cells and no EM disease were identified. Thirteen of 30 had additional hematopoietic neoplasms. The mean patient age was 74.1 years (median: 77 years, range: 43-91 years). No patients had lymphadenopathy (LAD) or splenomegaly by physical examination. By imaging, nine of 18 had LAD (8/9<1.5cm) and four of 18 had splenomegaly but with other attributable etiologies. Mean PB absolute lymphocyte count (ALC) was 1.8×10E9/L (range: 0.5-5.0×10E9/L). Twenty-four of 30 (80%) had low-level (<20%) BM involvement by MBL, and among these, none with available follow-up data progressed to diagnostic CLL/SLL. Six of 30 (20%) had >20% marrow involvement by MBL. Four of 6 were treated for CLL/SLL due to cytopenias, despite not meeting diagnostic criteria, and all 4 were CD38 or ZAP70 positive and had cytogenetic abnormalities, including trisomy 12. One of 6 developed overt CLL/SLL 3 years later and had cytogenetic abnormalities at the time of MBL diagnosis. One of 6 was monitored without treatment but had no cytogenetic abnormalities.Isolated BM CLL-type MBL represents a diagnostic gray area, and this study highlights the range of clinical outcomes. All cases with <20% BM involvement did not require CLL-specific treatment or progress to CLL/SLL. In the 4 cases where treatment was initiated due to cytopenias, patients had ≥20% BM involvement, CD38 or ZAP70 expression, and cytogenetic abnormalities but lacked a PB ALC of ≥5x10E9/L or LAD ≥1.5cm, suggesting that not all patients with clinically significant disease will meet criteria for CLL/SLL. The results also show that concurrent hematopoietic disorders can complicate the diagnosis, as the disease course or treatment may result in leukopenia, precluding PB absolute lymphocytosis. Though larger studies are needed, the degree of BM involvement, in conjunction with flow cytometric prognostic markers, and cytogenetic abnormalities may be a useful addition to the current diagnostic criteria for CLL/SLL which only considers a PB numerical cutoff and EM involvement.

P035 Subtle skin rash was the only presenting symptom of a premalignant condition; monoclonal B-cell lymphocytosis driven cryoglobulinaemic vasculitis, a case report

Abstract Background/Aims Intermittent episodes of subtle skin rash at the hands are commonly associated with dermatitis or allergy. We are reporting a case of cryoglobulinaemic vasculitis with a delayed diagnosis of more than two years because of subtle symptoms and normal investigations; highlighting important points to consider during the assessment of similar cases. Methods Case description: In June 2018, a 59-year-old man was initially assessed for intermittent episodes of pruritic skin rash usually on cold exposure, for the preceding 2 years. The patient described and showed pictures of non-blanching deep red-bluish plaques with raised irregular margins involving only the hands; usually self-resolving over 2-3 days without specific treatment and there were no defined predisposing factors. There was history of Raynaud’s, loss of appetite and weight loss of half a stone, but otherwise no other CTD/vasculitis symptoms. Clinical examination showed no skin, joints or systemic abnormalities. Investigations revealed positive RF at 30 U/mL, low C3 and C4 at 0.5 and &amp;lt; 0.1 g/L respectively; whereas full blood count, renal function, liver function, urine protein, ESR, CRP, immunoglobulins, s. protein electrophoresis, ANA, ANCA, HIV and hepatitis screen were all negative. Type 1 cryoglobulinaemia was detected at room temperature and cryoprecipitating IgG kappa was 3g/L on polyclonal background. Peripheral blood immune-phenotyping confirms kappa light chain and monoclonal B-cell lymphocytosis of CLL phenotype. Nailfold capillaroscopy revealed coiled capillaries and corkscrew ramification. CT-Chest abdomen pelvis showed widespread generalised lymphadenopathy. Over 3 years post diagnosis; there was no transformation of MBL to CLL clinically or haematologically except for episodes of rash, thus the plan was to continue monitoring for ‘B symptoms’, and to consider rituximab if significant symptoms appear. Results Cryoglobulins (immunoglobulins that precipitate in cold) are classified into three types: type I (monoclonal), type II (mixed) and type III (polyclonal). Polyclonal cryoglobulins are associated with autoimmune rheumatic diseases, hepatitis B and C. Mixed essential cryoglobulinaemia presents with purpuric skin lesions showing a leucocytoclastic vasculitis on biopsy. Type I monoclonal IgG, IgM, IgA, or their κ or λ light chains represent 10-15 % of the cases of cryoglobulinaemia. It is characterised by overwhelming association with hematologic neoplasia including MGUS, smouldering multiple myeloma, multiple myeloma, waldenström's macroglobulinemia, and chronic lymphocytic leukemia. Treatment is generally directed towards treating the underlying pre-malignant or malignant disorder. Conclusion Cryoglobulinaemia has a wide variety of clinical presentation scenarios, but physicians can play a key role by early recognition. In addition to the routine investigations, patients with suspected vasculitic rash especially to cold exposure need to be assessed for rheumatoid factor, complements and cryoglobulins, and cases confirmed with type I cryoglobulinaemia should be investigated for haematological malignancies. Nailfold Capillaroscopy is crucial in distinguishing secondary Raynaud’s, another feature of cryoglobulinaemia. Disclosure Z. Alkutobi: None. D. Laila: None. G. Ansari: None. A. Nandagudi: None.

Associations of history of vaccination and hospitalization due to infection with risk of monoclonal B-cell lymphocytosis

Associations of history of vaccination and hospitalization due to infection with risk of monoclonal B-cell lymphocytosis

Identification of a novel HOOK3-FGFR1 fusion gene involved in activation of the NF-kappaB pathway

BackgroundRearrangements involving the fibroblast growth factor receptor 1 (FGFR1) gene result in 8p11 myeloproliferative syndrome (EMS), which is a rare and aggressive hematological malignancy that is often initially diagnosed as myelodysplastic syndrome (MDS). Clinical outcomes are typically poor due to relative resistance to tyrosine kinase inhibitors (TKIs) and rapid transformation to acute leukemia. Deciphering the transcriptomic signature of FGFR1 fusions may open new treatment strategies for FGFR1 rearrangement patients.MethodsDNA sequencing (DNA-seq) was performed for 20 MDS patients and whole exome sequencing (WES) was performed for one HOOK3-FGFR1 fusion positive patient. RNA sequencing (RNA-seq) was performed for 20 MDS patients and 8 healthy donors. Fusion genes were detected using the STAR-Fusion tool. Fluorescence in situ hybridization (FISH), quantitative real-time PCR (qRT-PCR), and Sanger sequencing were used to confirm the HOOK3-FGFR1 fusion gene. The phosphorylation antibody array was performed to validate the activation of nuclear factor-kappaB (NF-kappaB) signaling.ResultsWe identified frequently recurrent mutations of ASXL1 and U2AF1 in the MDS cohort, which is consistent with previous reports. We also identified a novel in-frame HOOK3-FGFR1 fusion gene in one MDS case with abnormal monoclonal B-cell lymphocytosis and ring chromosome 8. FISH analysis detected the FGFR1 break-apart signal in myeloid blasts only. qRT-PCR and Sanger sequencing confirmed the HOOK3-FGFR1 fusion transcript with breakpoints located at the 11th exon of HOOK3 and 10th exon of FGFR1, and Western blot detected the chimeric HOOK3-FGFR1 fusion protein that is presumed to retain the entire tyrosine kinase domain of FGFR1. The transcriptional feature of HOOK3-FGFR1 fusion was characterized by the significant enrichment of the NF-kappaB pathway by comparing the expression profiling of FGFR1 fusion positive MDS with 8 healthy donors and FGFR1 fusion negative MDS patients. Further validation by phosphorylation antibody array also showed NF-kappaB activation, as evidenced by increased phosphorylation of p65 (Ser 536) and of IKBalpha (Ser 32).ConclusionsThe HOOK3-FGFR1 fusion gene may contribute to the pathogenesis of MDS and activate the NF-kappaB pathway. These findings highlight a potential novel approach for combination therapy for FGFR1 rearrangement patients.

COVID-19 vaccine failure in chronic lymphocytic leukaemia and monoclonal B-lymphocytosis; humoural and cellular immunity.

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 [<50AU/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 12months (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 <1000AU/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 ≥1000AU/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.

High Frequency of Low-Count Monoclonal B-Cell Lymphocytosis in Hospitalized COVID-19 Patients

High Frequency of Low-Count Monoclonal B-Cell Lymphocytosis in Hospitalized COVID-19 Patients

Understanding Monoclonal B Cell Lymphocytosis: An Interplay of Genetic and Microenvironmental Factors.

The term monoclonal B-cell lymphocytosis (MBL) describes the presence of a clonal B cell population with a count of less than 5 × 109/L and no symptoms or signs of disease. Based on the B cell count, MBL is further classified into 2 distinct subtypes: ‘low-count’ and ‘high-count’ MBL. High-count MBL shares a series of biological and clinical features with chronic lymphocytic leukemia (CLL), at least of the indolent type, and evolves to CLL requiring treatment at a rate of 1-2% per year, whereas ‘low-count’ MBL seems to be distinct, likely representing an immunological rather than a pre-malignant condition. That notwithstanding, both subtypes of MBL can carry ‘CLL-specific’ genomic aberrations such as cytogenetic abnormalities and gene mutations, yet to a much lesser extent compared to CLL. These findings suggest that such aberrations are mostly relevant for disease progression rather than disease onset, indirectly pointing to microenvironmental drive as a key contributor to the emergence of MBL. Understanding microenvironmental interactions is therefore anticipated to elucidate MBL ontogeny and, most importantly, the relationship between MBL and CLL.

Prevalence and Overall Survival of Low Count Monoclonal B-Cell Lymphocytosis (LC-MBL): A Screening Study of 8,297 Individuals from the Mayo Clinic Biobank

Prevalence and Overall Survival of Low Count Monoclonal B-Cell Lymphocytosis (LC-MBL): A Screening Study of 8,297 Individuals from the Mayo Clinic Biobank

TP53 Aberrations and Outcomes in MBL and Untreated CLL

TP53 Aberrations and Outcomes in MBL and Untreated CLL

Relationship and Susceptibility to Serious Infections Among Monoclonal B-Cell Lymphocytosis (MBL), Monoclonal Gammopathy of Undetermined Significance (MGUS), and Clonal Hematopoiesis (CH) Premalignant Conditions

Relationship and Susceptibility to Serious Infections Among Monoclonal B-Cell Lymphocytosis (MBL), Monoclonal Gammopathy of Undetermined Significance (MGUS), and Clonal Hematopoiesis (CH) Premalignant Conditions

Utilization of a Targeted Next Generation Sequencing Assay to Identify Copy Number Alterations in Chronic Lymphocytic Leukemia and Monoclonal B-Cell Lymphocytosis

Utilization of a Targeted Next Generation Sequencing Assay to Identify Copy Number Alterations in Chronic Lymphocytic Leukemia and Monoclonal B-Cell Lymphocytosis

Humoral and cellular immune responses to recombinant herpes zoster vaccine in patients with chronic lymphocytic leukemia and monoclonal B cell lymphocytosis.

Monoclonal B-cell lymphocytosis (MBL) and chronic lymphocytic leukemia (CLL) are clonal B-cell disorders associated with an increased risk of infections and impaired vaccination responses. We investigated the immunogenicity of recombinant zoster vaccine (RZV) in these patients. Individuals with MBL/untreated CLL and Bruton tyrosine kinase inhibitor (BTKi)-treated CLL patients were given two doses of RZV separated by 2 months. Responses assessed at 3 and 12 months from the first dose of RZV by an anti-glycoprotein E ELISA antibody assay and by dual-color Interferon-γ and Interleukin-2FLUOROSPOT assays were compared to historic controls matched by age and sex. About 62 patients (37 MBL/untreated CLL and 25 BTKi-treated CLL) were enrolled with a median age of 68 years at vaccination. An antibody response at 3 months was seen in 45% of participants, which was significantly lower compared to historic controls (63%, p= .03). The antibody response did not significantly differ between MBL/untreated CLL and BTKi-treated CLL (51% vs. 36%, respectively, p= .23). The CD4+ T-cell response to vaccination was significantly lower in study participants compared to controls (54% vs. 96%, p< .001), mainly due to lower responses among BTKi-treated patients compared to untreated MBL/CLL (32% vs. 73%, p= .008). Overall, only 29% of participants achieved combined antibody and cellular responses to RZV. Among participants with response assessment at 12 months (n= 47), 24% had antibody titers below the response threshold. Hypogammaglobulinemia and BTKi therapy were associated with reduced T-cell responses in a univariate analysis. Strategies to improve vaccine response to RZV among MBL/CLL patients are needed.

High-risk subtypes of chronic lymphocytic leukemia are detectable as early as 16 years prior to diagnosis

AbstractChronic lymphocytic leukemia (CLL) is preceded by monoclonal B-cell lymphocytosis (MBL), a CLL precursor state with a prevalence of up to 12% in aged individuals; however, the duration of MBL and the mechanisms of its evolution to CLL remain largely unknown. In this study, we sequenced the B-cell receptor (BcR) immunoglobulin heavy chain (IGH) gene repertoire of 124 patients with CLL and 118 matched controls in blood samples taken up to 22 years prior to diagnosis. Significant skewing in the BcR IGH gene repertoire was detected in the majority of patients, even before the occurrence of lymphocytosis and irrespective of the clonotypic IGH variable gene somatic hypermutation status. Furthermore, we identified dominant clonotypes belonging to major stereotyped subsets associated with poor prognosis up to 16 years before diagnosis in 14 patients with CLL. In 22 patients with longitudinal samples, the skewing of the BcR IGH gene repertoire increased significantly over time to diagnosis or remained stable at high levels. For 14 of 16 patients with available samples at diagnosis, the CLL clonotype was already present in the prediagnostic samples. Overall, our data indicate that the preclinical phase of CLL could be longer than previously thought, even in adverse-prognostic cases.

Characteristic bone marrow findings in patients with UBA1 somatic mutations and VEXAS syndrome

VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) is a newly characterized syndrome with underlying somatic UBA1 mutations in myeloid cells linking hematologic disease with autoinflammatory rheumatologic disorders. Hematologic abnormalities, particularly peripheral blood cytopenia(s) may prompt bone marrow evaluation in patients with known or unrecognized VEXAS syndrome. This review highlights key findings and diagnostic considerations encountered during bone marrow examination in patients with this disorder. Frequently reported hematologic changes include macrocytic anemia, cytoplasmic vacuoles in myeloid and erythroid precursors, marrow hypercellularity, and varying degrees of dysplasia. Myelodysplastic syndrome and plasma cell neoplasms have been diagnosed in patients with VEXAS syndrome. Macrophage activation syndrome and/or hemophagocytic lymphohistiocytosis and monoclonal B-cell lymphocytosis have also been reported. The bone marrow is a target organ in VEXAS syndrome. Heightened awareness of the bone marrow features and hematologic complications may aid in identifying individuals with VEXAS who may benefit from increased disease surveillance or alternative therapeutic strategies.

Benign and malignant hematologic manifestations in patients with VEXAS syndrome due to somatic mutations in UBA1

AbstractSomatic mutations in UBA1 involving hematopoietic stem and myeloid cells have been reported in patients with the newly defined VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome. Here, we report clinical hematologic manifestations and unique bone marrow (BM) features in 16 patients with VEXAS. All patients were male and had a history of severe autoinflammatory and rheumatologic manifestations and a somatic UBA1 mutation (p.Met41). Ten patients had hematologic disorders: myelodysplastic syndrome (MDS; 6 of 16), multiple myeloma (2 of 16), monoclonal gammopathy of undetermined significance (2 of 16), and monoclonal B-cell lymphocytosis (2 of 16), and a few of those patients had 2 co-existing clonal processes. Although macrocytic anemia (100%) and lymphopenia (80%) were prevalent in all patients with VEXAS, thrombocytopenia and neutropenia were more common in patients with progression to MDS. All BMs in VEXAS patients had prominent cytoplasmic vacuoles in myeloid and erythroid precursors. In addition, most BMs were hypercellular with myeloid hyperplasia, erythroid hypoplasia, and varying degrees of dysplasia. All patients diagnosed with MDS were lower risk (low blast count, very good to intermediate cytogenetics) according to standard prognostic scoring with no known progression to leukemia. In addition, 10 of 16 patients had thrombotic events, including venous thromboembolism and arterial stroke. Although VEXAS presents symptomatically as a rheumatologic disease, morbidity and mortality are associated with progression to hematologic disease. Given the increased risk of developing MDS and multiple myeloma, surveillance for disease progression is important.

Polygenic risk score and risk of monoclonal B-cell lymphocytosis in caucasians and risk of chronic lymphocytic leukemia (CLL) in African Americans

Monoclonal B-cell lymphocytosis (MBL) is a precursor to CLL. Other than age, sex, and CLL family-history, little is known about factors associated with MBL risk. A polygenic-risk-score (PRS) of 41 CLL-susceptibility variants has been found to be associated with CLL risk among individuals of European-ancestry(EA). Here, we evaluate these variants, the PRS, and environmental factors for MBL risk. We also evaluate these variants and the CLL-PRS among African-American (AA) and EA-CLL cases and controls. Our study included 560 EA MBLs, 869 CLLs (696 EA/173 AA), and 2866 controls (2631 EA/235 AA). We used logistic regression, adjusting for age and sex, to estimate odds ratios (OR) and 95% confidence intervals within each race. We found significant associations with MBL risk among 21 of 41 variants and with the CLL-PRS (OR = 1.86, P = 1.9 × 10−29, c-statistic = 0.72). Little evidence of any association between MBL risk and environmental factors was observed. We observed significant associations of the CLL-PRS with EA-CLL risk (OR = 2.53, P = 4.0 × 10−63, c-statistic = 0.77) and AA-CLL risk (OR = 1.76, P = 5.1 × 10−5, c-statistic = 0.62). Inherited genetic factors and not environmental are associated with MBL risk. In particular, the CLL-PRS is a strong predictor for both risk of MBL and EA-CLL, but less so for AA-CLL supporting the need for further work in this population.

Abstract 884: Tumor mutational load derived from recurrently mutated genes in chronic lymphocytic leukemia (CLL) predicts time-to-first treatment in high-count monoclonal B-cell lymphocytosis (HC MBL)

Abstract Clinical practice guidelines recommend that individuals with HC MBL are evaluated annually for evidence of progression as it has been shown that they progress to develop CLL requiring therapy at a rate of 1-5%/year. Next-generation sequencing identified 59 genes recurrently mutated in CLL, and we previously showed that the tumor mutational load (TML), i.e., the total number of these genes mutated, is associated with a shorter time to first treatment (TTT) among 112 HC MBLs independent of the CLL international prognostic index (CLL-IPI), an established prognostic score. Herein, we continue to support our finding in additional HC MBLs and report the pooled results across the two cohorts. From the Mayo Clinic CLL Resource, we sequenced a total 167 HC MBL (112 from the initial round and 55 from additional sequencing). We extracted DNA from CD5+/CD19+ B-cells and sequenced the coding regions of 59 driver genes. Somatic mutations were called using MuTect2 in tumor-only mode. Germline variants were eliminated based on minor allele frequencies &amp;gt;0.01% and by those identified in public databases, unless present in known CLL mutation hotspots. After filtering, we computed the TML based on the number of genes with high impact (nonsense, frameshift and splicing) and hotspot mutations. Cox regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI), adjusted for sex and CLL-IPI. Stratified analyses were conducted by low/intermediate risk and high/very high CLL-IPI. Of the 167 HC MBL, low risk CLL-IPI comprised 60%, intermediate risk 28%, high risk 12%; and none were very-high risk. The most commonly mutated genes were SF3B1 (11%), NOTCH1 (9%), TP53 (7%), BIRC3 (7%), and MYD88 (6%); and 52 (31%) individuals had mutations in at least one gene. The median follow-up was 4.4 years, and 26 of the 167 individuals progressed to CLL requiring therapy. HC MBL with ≥2 mutated genes had a 28% 5-year risk of needing therapy compared to 6% among those with no mutated genes. Similar to our initial finding (HR=1.53, CI:1.12-2.07; P=0.007), we found a shorter TTT in the additional HC MBLs (HR=4.63, CI:1.57-13.7, P=0.006), and in the pooled cohort (HR=1.72; CI:1.29-2.28, P=0.0002). When we stratified by CLL-IPI risk, TML remained associated with TTT among individuals with low/intermediate CLL-IPI risk in the additional HC MBLs (HR=3.52, CI:1.11-11.2, P=0.03) and in the pooled cohort (HR=2.25, CI:1.34-3.77, P=0.002). A non-significant 2.8 fold association was observed with high risk CLL-IPI in the pooled cohort. In conclusion, the TML along with the CLL-IPI provide clinicians with a more accurate prognostic information regarding disease progression requiring therapy, especially for those MBLs with low to intermediate risk based on CLL-IPI. If validated, these findings may modify current practice guidelines for individuals with HC MBL. Citation Format: Geffen Kleinstern, Cecilia Bonolo de Campos, Nicholas J. Boddicker, Daniel R. O'Brien, Shulan Tian, Chantel Barney, Kari G. Rabe, Cristine Allmer, Laura Bruins, Aaron D. Norman, Timothy G. Call, Sameer A. Parikh, Jose F. Leis, Wei Ding, Huihuang Yan, James R. Cerhan, Neil E. Kay, Celine Vachon, Esteban Braggio, Susan L. Slager. Tumor mutational load derived from recurrently mutated genes in chronic lymphocytic leukemia (CLL) predicts time-to-first treatment in high-count monoclonal B-cell lymphocytosis (HC MBL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 884.