Recommendations for the diagnosis and initial evaluation of patients with Waldenström Macroglobulinaemia: A Task Force from the 8th International Workshop on Waldenström Macroglobulinaemia

Bruton Tyrosine Kinase Inhibition: an Effective Strategy to Manage Waldenström Macroglobulinemia

PURPOSE OF REVIEW

The treatment of Waldenström macroglobulinemia (WM) has evolved over the past decade. With the seminal discoveries of MYD88 and CXCR warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) mutations in WM cells, our understanding of the disease biology and treatment has improved. The development of a new class of agents, Bruton tyrosine kinase inhibitors (BTKi), has substantially impacted the treatment paradigm of WM. Herein, we review the current and emerging BTKi and the evidence for their use in WM.

RECENT FINDINGS

Clinical trials have established the role of covalent BTKi in the treatment of WM. Their efficacy is compromised among patients who harbor CXCR4WHIM mutation or MYD88WT genotype. The development of BTKC481 mutation-mediated resistance to covalent BTKi may lead to disease refractoriness. Novel, non-covalent, next-generation BTKi are emerging, and preliminary results of the early phase clinical trials show promising activity in WM, even among patients refractory to a covalent BTKi. Covalent BTK inhibitors have demonstrated meaningful outcomes in treatment-naïve (TN) and relapsed refractory (R/R) WM, particularly among those harboring the MYD88L265P mutation. The next-generation BTKi demonstrate improved selectivity, resulting in a more favorable toxicity profile. In WM, BTKi are administered until progression or the development of intolerable toxicity. Consequently, the potential for acquired resistance, the emergence of cumulative toxicities, and treatment-related financial burden are critical challenges associated with the continuous therapy approach. By circumventing BTK C481 mutations that alter the binding site to covalent BTKi, the non-covalent BTKi serve as alternative agents in the event of acquired resistance. Head-to-head comparative trials with the conventional chemoimmunotherapies are lacking. The findings of the RAINBOW trial (NCT046152), comparing the dexamethasone, rituximab, and cyclophosphamide (DRC) regimen to the first-generation, ibrutinib are awaited, but more studies are needed to draw definitive conclusions on the comparative efficacy of chemoimmunotherapy and BTKi. Complete response is elusive with BTKi, and combination regimens to improve upon the efficacy and limit the treatment duration are also under evaluation in WM.

The performance and applied value of 18F-FDG PET/CT imaging in Waldenstrom macroglobulinemia

Waldenstrom macroglobulinemia (WM) is a rare inert B lymphocyte lymphoma and the role of FDG PET/CT imaging in WM has not been well established. This study aimed to evaluate the metabolic status of WM by 18F-FDG PET/CT imaging. We retrospectively analyzed 20 patients who underwent pretherapy 18F-FDG PET-CT scan. All patients were diagnosed by bone marrow aspiration, laboratory examination and clinical symptoms. Bone marrow involvement was identified with 18F-FDG PET/CT imaging in 16 of 20, and the mean SUVmax of bone marrow was 4.06±0.85, Lymph nodes were involved in 8 of 20 patients, and the mean SUVmax of Lymph nodes was 4.07±1.27. Liver and spleen were involved in one case respectively, with SUVmax being 3.6 and 3.3. 1 case of extramedullary infiltration and 1 case of lymphomatous transformation. 18F-FDG PET/CT imaging not only could reveal the metabolic status of lymph nodes, liver, spleen and bone marrow in WM patients, but also evaluate the status of tumor burden which helps to formulate personalized treatment plans.

Multimodal Imaging Characteristics and Risk Factors Analysis of Waldenström Macroglobulinemia Retinopathy

PURPOSE

To summarize the multimodal imaging features and analyze the risk factors of Waldenström macroglobulinemia retinopathy (WMR).

DESIGN

Retrospective, cross-sectional study.

METHODS

Patients diagnosed with WM and underwent ophthalmic examination in Peking Union Medical College Hospital in the last decade were included. Multimodal imaging characteristics of WMR were summarized. Univariate and multivariate logistic regression analysis of WMR and potential systemic and ocular factors was performed.

RESULTS

A total of 50 patients with WM were included in this study, and 28 patients had WMR in at least 1 eye. WMR was found to have worse LogMAR visual acuity (0.52 ± 0.54 vs 0.21 ± 0.18, P = .009) and was characterized by tortuous retinal vessels, extensive retinal hemorrhage, distinctive shape of macular edema, and so on. In univariate analysis, the presence of WMR was significantly associated with the mean visual acuity (LogMAR), serum red blood cell counts, serum platelet counts, hemoglobin level, serum M protein, serum IgM level, and lactate dehydrogenase (with P < .05). In multivariate analysis, WMR was significantly correlated with M protein (adjusted odds ratio = 1.127, 95% CI: 1.052-1.209, P= .001) and serum IgM (adjusted odds ratio = 1.059, 95% CI: 1.023-1.095, P = .001) with the predicted areas under the curve of 0.859 and 0.820, respectively. The optimal cutoff values were 26.2 g/L for M protein and 51.0 g/L for IgM, which accounts for a sensitivity of 95.4% and 95.4% and specificity of 64.3% and 60.7%, respectively.

CONCLUSIONS

WMR has specific characteristics in ophthalmic examinations. Serum IgM levels and M protein are good predictors of WMR, which could attach important value of fundus examinations for patients with WM.

New developments in the diagnosis and characterization of Waldenström's macroglobulinemia

INTRODUCTION

Waldenström's macroglobulinemia (WM) is defined as a lymphoplasmacytic lymphoma (LPL) with immunoglobulin M (IgM) monoclonal gammopathy and morphologic evidence of bone marrow infiltration by LPL. Immunophenotyping and genotyping provide a firm pathological basis for diagnosis and are particularly valuable in differential diagnosis between WM and related diseases. Emerging technologies in mutational analysis present new opportunities, but challenges remain around standardization of methodologies and reporting of mutational data across centers.

AREAS COVERED

The review provides an overview of the diagnosis of WM, with a particular focus on the role of immunophenotyping and genotyping.

EXPERT OPINION

Demonstration of LPL with a bone marrow biopsy is essential to reach a definitive diagnosis of WM. However, MYD88L265P and a typical WM immunophenotypic profile are valuable for the differential diagnosis of WM and related diseases, such as marginal zone lymphoma, multiple myeloma, and chronic lymphocytic leukemia. These methodologies must be utilized across centers and with appropriate standards followed in the evaluation and reporting of sensitivities and specificities. The diagnostic and/or prognostic value of mutations in genes such as CXCR4 and TP53 that are currently not routinely evaluated in the diagnosis of WM should be explored.

Dysfunctions of innate and adaptive immune tumor microenvironment in Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a rare subtype of non-Hodgkin lymphoma characterized by malignant lymphoplasmacytic cells in the bone marrow (BM). To dissect the pathophysiology of WM, we evaluated clonal cells by mapping of B cell lymphomagenesis with adaptive and innate immune tumor microenvironment (TME) in the BM of WM patients using mass cytometry (CyTOF). In-depth immunophenotypic profiling of WM cells exhibited profound expansion of clonal cells in both unswitched and switched memory B cells and also plasma cells with aberrant expression variations. WM B lymphomagenesis was associated with reduction of most B cell precursors assessed with the same clonally restricted light chain and phenotypic changes. The immune TME was infiltrated by mature monocytes, neutrophils and adaptive T cells, preferentially subsets of effector T helper, effector CTL and effector memory CTL cells that were associated with superior overall survival (OS), in contrast to progenitors of T cells and myeloid/monocytic lineage subsets that were suppressed in WM cohort. Moreover, decrease in immature B and NKT cells was related to worse OS in WM patients. Innate and adaptive immune subsets of WM TME were modulated by immune checkpoints, including PD-1/PD-L1&PD-L2, TIGIT/PVR, CD137/CD137-L, CTLA-4, BTLA and KIR expression. The response of ibrutinib treatment to the reduction of clonal memory B cell was associated with high levels of immature B cells and effector memory CTL cells. Our study demonstrates that CyTOF technology is a powerful approach for characterizing the pathophysiology of WM at various stages, predicting patient risk and monitoring the effectiveness of treatment strategies.

Laboratory and Clinical Settings of Heavy/Light Chain (HLC) Assays in the Management of Monoclonal Gammopathies and Multiple Myeloma

The antibody-related immune response is mediated by immunoglobulins (Igs), soluble circulating glycoproteins produced by activated B cells that, upon the recognition of specific epitopes on pathogen surfaces, activate, proliferate, and differentiate into antibody-secreting plasma cells. Although the antibodies are effectors of the humoral immune adaptive response, their overproduction in response to a dysregulated proliferation of clonal plasma cell production in tumoral conditions (i.e., multiple myeloma), enriches the serum and urinary matrices, assuming the crucial role of biomarkers. Multiple myeloma (MM) is a plasma cell dyscrasia characterized by the expansion and accumulation of clonally activated plasma cells in bone marrow, determining the release of high amounts of monoclonal component (MC) that can be detected as intact immunoglobulin (Ig), immunoglobulin fragments, or free light chains (FLCs). The importance of detecting biomarkers for the diagnosis, monitoring, and prognosis of diseases is highlighted by the international guidelines that recommend specific assays for the analysis of intact Igs and FLC. Moreover, a developed assay called Hevylite^® allows for the quantification of immunoglobulins that are both involved (iHLC) and not involved (uHLC) in the tumor process; this is a fundamental aspect of following up the patient's workup and evaluating the progression of disease, together with the treatments response. We here summarize the major points of the complex scenario involving monoclonal gammopathies and MM clinical management in view of advantages derived for the use of Hevylite^®.

Prognostic impact of MYD88 and CXCR4 mutations assessed by droplet digital polymerase chain reaction in IgM monoclonal gammopathy of undetermined significance and smouldering Waldenström macroglobulinaemia

Waldenström macroglobulinaemia (WM) is characterized by recurrent somatic mutations in MYD88 and CXCR4 genes. However, limitations arise when analysing these mutations in IgM monoclonal gammopathy of undetermined significance (MGUS) or smouldering WM (SWM) given the lower tumour load. Here, we used droplet digital polymerase chain reaction (ddPCR) to analyse MYD88 L265P and CXCR4 S338* mutations (C1013G and C1013A) in unsorted bone marrow (BM) or cell-free DNA (cfDNA) samples from 101 IgM MGUS and 69 SWM patients. ddPCR was more sensitive to assess MYD88 L265P compared to allele-specific PCR, especially in IgM MGUS (64% vs 39%). MYD88 mutation burden correlated with other laboratory biomarkers, particularly BM infiltration (r = 0.8; p < 0.001). CXCR4 C1013G was analysed in MYD88-mutated samples with available genomic DNA and was detected in 19/54 (35%) and 18/42 (43%) IgM MGUS and SWM cases respectively, also showing correlation with BM involvement (r = 0.9; p < 0.001). ddPCR also detected 8 (38%) and 10 (63%) MYD88-mutated cfDNA samples in IgM MGUS and SWM respectively. Moreover, high BM mutation burden (≥8% MYD88 and ≥2% CXCR4) was associated with an increased risk of progression to symptomatic WM. We show the clinical applicability of ddPCR to assess MYD88 and CXCR4 in IgM MGUS and SWM and provide a molecular-based risk classification.

Diagnostics in Waldenström's macroglobulinemia: a consensus statement of the European Consortium for Waldenström's Macroglobulinemia

The diagnosis of Waldenström's macroglobulinemia (WM), an IgM-associated lymphoplasmacytic lymphoma, can be challenging due to the different forms of disease presentation. Furthermore, in recent years, WM has witnessed remarkable progress on the diagnostic front, as well as a deeper understanding of the disease biology, which has affected clinical practice. This, together with the increasing variety of tools and techniques available, makes it necessary to have a practical guidance for clinicians to perform the initial evaluation of patients with WM. In this paper, we present the consensus recommendations and laboratory requirements for the diagnosis of WM developed by the European Consortium of Waldenström's Macroglobulinemia (ECWM), for both clinical practice as well as the research/academical setting. We provide the procedures for multiparametric flow cytometry, fluorescence in situ hybridization and molecular tests, and with this offer guidance for a standardized diagnostic work-up and methodological workflow of patients with IgM monoclonal gammopathy of uncertain significance, asymptomatic and symptomatic WM.

Managing Waldenström's macroglobulinemia with BTK inhibitors

Bruton's tyrosine kinase (BTK) inhibition is one of the treatment standards for patients with relapsed/refractory Waldenström's macroglobulinemia (WM) and for patients with WM who are unsuitable for immunochemotherapy (ICT). It offers deep and durable responses with a manageable safety profile that is generally favorable compared with ICT regimens. However, the limitations of the first approved BTK inhibitor (BTKi), ibrutinib, include reduced efficacy in patients lacking the characteristic WM mutation (MYD88L265P) and toxicities related to off-target activity. The risk of atrial fibrillation (AF) and other cardiovascular side effects are a notable feature of ibrutinib therapy. Several next-generation covalent BTKis with greater selectivity for BTK are at various stages of development. In November 2021, zanubrutinib became the first of these agents to be approved by the European Medicines Agency for the treatment of WM. Head-to-head trial data indicate that it has comparable efficacy to ibrutinib for patients with WM overall, although it may be more effective in patients with CXCR4 mutations or wild-type MYD88. In the clinical trial setting, its greater selectivity translates into a reduced risk of cardiovascular side effects, including AF. Acalabrutinib, which is pre-approval in WM, appears to offer similar advantages over ibrutinib in terms of its safety profile. Beyond the next-generation covalent BTKis, non-covalent BTKis are an emerging class with the potential to provide a therapeutic option for patients who relapse on covalent BTKis. In the future, BTKis may be increasingly utilized within combination regimens. Several ongoing trials in WM are investigating the potential for BTKi use in combination with established and novel targeted agents.

Diagnosis and management of AL amyloidosis due to B-cell non-Hodgkin lymphoma

Immunoglobulin light chain (AL) amyloidosis may be caused by a B-cell non-Hodgkin lymphoma (NHL) rather than a plasma cell neoplasm in rare cases, which presents unique diagnostic and management considerations. NHL associated with AL will often have an IgM paraprotein; thus, this disease is termed IgM-related AL amyloidosis (IgM AL). The clinical presentation of IgM AL is more likely to involve the lungs, peripheral nerves, and soft tissue; cardiac involvement is less common. Patients with IgM AL amyloidosis should undergo a lymphoma-directed work-up including evaluation for nodal and extranodal disease. Additionally, patients with an IgM paraproteinemia should be screened for AL amyloidosis through history and physical examination. Treatment regimens active against underlying lymphoma, rather than plasma cell-directed regimens, are recommended. Historical response rates in IgM AL have been poor; prospective studies of novel antineoplastic regimens may improve treatment outcomes.

Study of heat sink effect of blood in a bifurcated vessel

Thermal ablation treatment uses elevated (hyperthermia) or depressed (hypothermia) tissue temperature to destroy tumor cells. The efficacy and effectiveness of thermal ablation therapy is dependent on the tissue temperature which is significantly affected due to heat sink effect of blood flow near the infected site. In this study, Euler-Euler multiphase model is used to analyze the effect of plasma and RBC concentration on the heat sink effect of blood in a bifurcated vessel. This study is divided into two separate cases. First case refers to the study of heat sink effect produced by a tumor patient suffering from HVS (hyperviscosity syndrome) and a normal (without blood disorder) tumor patient during hyperthermia treatment. The second case analyses the effect of RBCs on blood heat transfer. Temperature distribution and transient Nusselt number, which are used to represent heat sink effect, are calculated and compared for different cases of blood disorders. From the results, it is found that a patient with HVS blood disorder produces a smaller heat sink effect during hyperthermia treatment compared to a normal tumor patient. Also, the level of RBC concentration in the blood stream has a minimal effect on heat transfer.

Mono/polyclonal free light chains as challenging biomarkers for immunological abnormalities

Free light chain (FLC) kappa (k) and lambda (λ) consist of low molecular weight proteins produced in excess during immunoglobulin synthesis and secreted into the circulation. In patients with normal renal function, over 99% of FLCs are filtered and reabsorbed. Thus, the presence of FLCs in the serum is directly related to plasma cell activity and the balance between production and renal clearance. FLCs are bioactive molecules that may exist as monoclonal (m) and polyclonal (p) FLCs. These have been detected in several body fluids and may be key indicators of ongoing damage and/or illness. International guidelines now recommend mFLC for screening, diagnosis and monitoring multiple myeloma and other plasma cell dyscrasias. In current clinical practice, FLCs in urine indicate cast nephropathy and other renal injury, whereas their presence in cerebrospinal fluid is important for identifying central nervous system inflammatory diseases such as multiple sclerosis. Increased pFLCs have also been detected in various conditions characterized by B cell activation, i.e., chronic inflammation, autoimmune disease and HCV infection. Monitoring the coronavirus (COVID-19) pandemic by analysis of salivary FLCs presents a significant opportunity in clinical immunology worthy of scientific pursuit.

Does early disease progression predicts survival after first line-treatment of Waldenström macroglobulinemia?

In symptomatic Waldenström macroglobulinemia (sWM) patients, prognosis is assessed with the international prognostic scoring system (IPSSWM). In follicular lymphoma and other B‐cell and T‐cell lymphomas, disease progression within 24 months (POD24) or (in patients without POD24) after 24 months has been proposed as the start date for stratifying subsequent survival. In the present report, we assessed in a large series of 472 sWM patients, the prognostic value of this new dynamic endpoint already reported in many other lymphomas subtypes. The 3 year subsequent survival for patients with POD24 was 75% and 93% for patients without POD24. In sWM patients, departure from the proportional hazards assumption complicated this analysis. In patients without POD24, the median subsequent progression‐free survival time of 43 months accounted for favorable outcome, whereas survival after progression was not influenced by the time to progression. In addition, sensitivity analysis showed that the baseline IPSSWM score also influenced survival after POD24. In sWM patients, we conclude that the apparent difference in survival after POD24 or the 24 months time‐point (in patients without POD24) is mainly explained by the prolonged subsequent progression free survival of latter patients. Indeed, the mortality after progression is not influenced by the time to this event.

Diagnosis and management of Waldenström macroglobulinaemia-A British Society for Haematology guideline

SCOPE

The objective of this guideline is to provide healthcare professionals with clear guidance on the management of patients with Waldenström macroglobulinaemia. In individual patients, circumstances may dictate an alternative approach.

METHODOLOGY

This guideline was compiled according to the British Society for Haematology (BSH) process at http://www.b-s-h.org.uk/guidelines/proposing-and-writing-a-new-bsh-guideline/. Recommendations are based on a review of the literature using Medline, Pubmed, Embase, Central, Web of Science searches from beginning of 2013 (since the publication of the previous guidelines) up to November 2021. The following search terms were used: Waldenström('s) macroglobulin(a)emia OR lymphoplasmacytic lymphoma, IgM(-related) neuropathy OR cold h(a)emagglutinin disease OR cold agglutinin disease OR cryoglobulin(a)emia AND (for group a only) cytogenetic OR molecular OR mutation OR MYD88 OR CXCR4, management OR treatment OR transfusion OR supportive care OR plasma exchange OR plasmapheresis OR chemotherapy OR bendamustine OR bortezomib OR ibrutinib OR fludarabine OR dexamethasone OR cyclophosphamide OR rituximab OR everolimus, bone marrow transplantation OR stem cell transplantation. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) nomenclature was used to evaluate levels of evidence and to assess the strength of recommendations. The GRADE criteria can be found at http://www.gradeworkinggroup.org. Review of the manuscript was performed by the British Society for Haematology (BSH) Guidelines Committee Haemato-Oncology Task Force, the BSH Guidelines Committee and the Haemato-Oncology sounding board of BSH. It was also on the members section of the BSH website for comment. It has also been reviewed by UK Charity WMUK; these organisations do not necessarily approve or endorse the contents.

Primary central nervous system diffuse large B-cell lymphoma masqueraded as Bing-Neel syndrome: Steps in management and review of future directions

Bing-Neel syndrome (BNS) remains a rare complication of Waldenstrom Macroglobulinemia. Given the paucity of this disease, treatment guidelines are based on small clinical trials with limited participants. Here, we present a case of primary CNS diffuse large B-cell lymphoma masqueraded as BNS that developed while on ibrutinib therapy.

Determination of MYD88L265P mutation fraction in IgM monoclonal gammopathies

Quantitative evaluation of the tumor load in patients with IgM monoclonal gammopathies in tDNA and cfDNA samples.

We describe a novel method for the detection of MYD88^L265P mutation using a competitive allele-specific polymerase chain reaction (Cast-PCR) assay. This assay has a sensitivity of 1 × 10⁻³, is applicable in reactions containing very low amounts of DNA (as low as 20 pg), and allowed the detection of MYD88^L265P somatic mutation in both tumor-derived DNA (tDNA) and cell-free DNA (cfDNA). In addition, using the Cast-PCR assay, we were able to determine the mutation allele fraction (MAF) in each tested sample. We then analyzed baseline tDNA and cfDNA samples from 163 patients (53 with immunoglobulin M monoclonal gammopathy of undetermined significance and 110 with Waldenström’s macroglobulinemia [WM], of whom 54 were asymptomatic and 56 were symptomatic) and also in sequential samples of 37 patients. MAF in both cfDNA and tDNA was higher among patients with symptomatic compared with asymptomatic WM and in those with asymptomatic WM compared with those with immunoglobulin M (IgM) monoclonal gammopathy of undetermined significance. In addition, the evaluation of sequential samples showed that MAF decreased after treatment, whereas it increased in patients who relapsed or progressed to symptomatic WM. Thus, Cast-PCR is a highly sensitive, cost-effective diagnostic tool for MYD88^L265P detection, applicable in both tDNA and cfDNA samples, that also provides a quantitative evaluation of the tumor load in patients with IgM monoclonal gammopathies.

Waldenström's Macroglobulinemia: An Exploration into the Pathology and Diagnosis of a Complex B-Cell Malignancy

After 77 years since the initial description, Waldenström macroglobulinemia (WM) remains as a bone marrow neoplastic disorder with lymphoplasmacytic differentiation oversecreting a monoclonal immunoglobulin M (IgM). However, many biological and genetic aspects of this entity have been unraveled and it is now easy to correctly diagnose patients with this illness. The diagnosis requires the presence of a monoclonal IgM component and bone marrow lymphoid infiltration must be demonstrated. In addition, other small B-cell lymphoid neoplasms with plasma cell differentiation must be discarded. Although the clinical picture is highly heterogeneous, the diagnosis is much easier today compared to the past, since now we can demonstrate the presence of somatic mutations, especially the L265P mutation in the MYD88 gene, highly characteristic of WM (>90% of the patients), followed by the WHIM-like mutations in the CXCR4 gene (~35%). The identification of these mutations is very important, because they can modulate the response to new treatments with Bruton's tyrosine kinase (BTK) inhibitors. Thus, the conventional prognostic factors that predict the outcome of these patients (anemia, thrombopenia, high M component, high B2M, and advanced age), must be complemented with the genetic evaluation of the patient, that can help us in the prediction of the risk of transformation from asymptomatic to symptomatic forms (Del6q) and/or from indolent forms of the disease to aggressive lymphomas (CD79b mutations).

Iceland screens, treats, or prevents multiple myeloma (iStopMM): a population-based screening study for monoclonal gammopathy of undetermined significance and randomized controlled trial of follow-up strategies

Monoclonal gammopathy of undetermined significance (MGUS) precedes multiple myeloma (MM). Population-based screening for MGUS could identify candidates for early treatment in MM. Here we describe the Iceland Screens, Treats, or Prevents Multiple Myeloma study (iStopMM), the first population-based screening study for MGUS including a randomized trial of follow-up strategies. Icelandic residents born before 1976 were offered participation. Blood samples are collected alongside blood sampling in the Icelandic healthcare system. Participants with MGUS are randomized to three study arms. Arm 1 is not contacted, arm 2 follows current guidelines, and arm 3 follows a more intensive strategy. Participants who progress are offered early treatment. Samples are collected longitudinally from arms 2 and 3 for the study biobank. All participants repeatedly answer questionnaires on various exposures and outcomes including quality of life and psychiatric health. National registries on health are cross-linked to all participants. Of the 148,704 individuals in the target population, 80 759 (54.3%) provided informed consent for participation. With a very high participation rate, the data from the iStopMM study will answer important questions on MGUS, including potentials harms and benefits of screening. The study can lead to a paradigm shift in MM therapy towards screening and early therapy.

Management of Waldenström macroglobulinemia in 2020

The management of Waldenström macroglobulinemia (WM) has evolved tremendously with recent genomic discoveries that correlate with clinical presentation and could help to tailor treatment approaches. The current diagnosis of WM requires clinicopathological criteria, including bone marrow involvement by lymphoplasmacytic lymphoma cells, a serum immunoglobulin M (IgM) monoclonal paraprotein, and presence of the MYD88 L265P mutation. Once the diagnosis is established, the relationship between the patient's symptoms and WM should be carefully investigated, because therapy should be reserved for symptomatic patients. Bone marrow involvement and serum levels of IgM, albumin, and β2-microglobulin can be used to estimate the time until treatment initiation. The treatment of WM patients should be highly personalized, and the patient's clinical presentation, comorbidities, genomic profile, and preferences, as well as toxicity of the treatment regimens, should be taken into account. Alkylating agents (bendamustine, cyclophosphamide), proteasome inhibitors (bortezomib, carfilzomib, ixazomib), anti-CD20 monoclonal antibodies (rituximab, ofatumumab), and Bruton tyrosine kinase (BTK) inhibitors (ibrutinib, acalabrutinib, zanubrutinib) are safe and highly effective treatment options in patients with WM. Because novel covalent and noncovalent BTK inhibitors (tirabrutinib, vecabrutinib, LOXO-305, ARQ-531), BCL2 antagonists (venetoclax), and CXCR4-targeting agents (ulocuplumab, mavorixafor) are undergoing clinical development in WM, the future of WM therapy certainly appears bright and hopeful.

B-Cell-Specific Myd88 L252P Expression Causes a Premalignant Gammopathy Resembling IgM MGUS

A highly recurrent somatic L265P mutation in the TIR domain of the signaling adapter MYD88 constitutively activates NF-κB. It occurs in nearly all human patients with Waldenström’s macroglobulinemia (WM), a B cell malignancy caused by IgM-expressing cells. Here, we introduced an inducible leucine to proline point mutation into the mouse Myd88 locus, at the orthologous position L252P. When the mutation was introduced early during B cell development, B cells developed normally. However, IgM-expressing plasma cells accumulated with age in spleen and bone, leading to more than 20-fold elevated serum IgM titers. When introduced into germinal center B cells in the context of an immunization, the Myd88^L252P mutation caused prolonged persistence of antigen-specific serum IgM and elevated numbers of antigen-specific IgM plasma cells. Myd88^L252P-expressing B cells switched normally, but plasma cells expressing other immunoglobulin isotypes did not increase in numbers, implying that IgM expression may be required for the observed cellular expansion. In order to test whether the Myd88^L252P mutation can cause clonal expansions, we introduced it into a small fraction of CD19-positive B cells. In this scenario, five out of five mice developed monoclonal IgM serum paraproteins accompanied by an expansion of clonally related plasma cells that expressed mostly hypermutated VDJ regions. Taken together, our data suggest that the Myd88^L252P mutation is sufficient to promote aberrant survival and expansion of IgM-expressing plasma cells which in turn can cause IgM monoclonal gammopathy of undetermined significance (MGUS), the premalignant condition that precedes WM.

Oncologic Emergencies: Traditional and Contemporary

The recognition and management of oncologic emergencies are becoming increasingly relevant in the intensive care unit, particularly in the era of novel biologic therapies. Early recognition and multidisciplinary collaboration are essential to improving patient outcomes. This article discusses aspects of diagnosis and management for important malignancy-associated emergencies.

Diagnostic value of bone marrow core biopsy patterns in lymphoplasmacytic lymphoma/Waldenström macroglobulinaemia and description of its mutational profiles by targeted NGS

AIMS

The aim of this study was to describe the characteristics of the bone marrow infiltration found in a series of clinically defined lymphoplasmacytic lymphoma (LPL)/Waldenström macroglobulinaemia (WM) and IgM-monoclonal gammopathy of undetermined significance (MGUS) and to perform a targeted next-generation sequencing (NGS) for the identification of additional somatic mutations to MYD88p.L265P in LPL/WM.

METHODS

We have reviewed a series of 35 bone marrow biopsies from 28 patients with a clinical diagnosis of LPL/WM (24 cases) or MGUS (4 cases). Bone marrow infiltration characteristics by morphology, immunohistochemistry, flow cytometry (FCM), allele-specific real-time PCR for the detection of MYD88p.L265P mutation, targeted exonic amplicon-based NGS of 35 lymphoma-related genes and direct sequencing were analysed.

RESULTS

Our findings show that bone marrow trephine biopsy evaluation is superior to FCM in the identification of significant lymphoid infiltrates. A combined paratrabecular and interstitial infiltration pattern is the most common feature in LPL/WM while a patchy interstitial pattern characterises IgM-MGUS cases. MYD88p.L265P mutation was found by allele-specific-PCR in 92% of the LPL cases (22 out of 24) and 25% of IgM-MGUS cases (1 out of 4 cases). In addition to MYD88p.L265P somatic mutations in CXCR4, KMT2D, PRDM1/Blimp1, MYC and ID3 were found by NGS and direct sequencing in 4 cases.

CONCLUSIONS

In conclusion, bone marrow core biopsy evaluation is critical in the identification of unequivocal bone marrow infiltration by LPL/WM. In addition to MYD88p.L265P, somatic mutations in CXCR4, KMT2D, PRDM1/Blimp1, MYC and ID3 can appear in a fraction of LPL/WM.

Clinical and molecular characteristics of lymphoplasmacytic lymphoma not associated with an IgM monoclonal protein: A multicentric study of the Rete Ematologica Lombarda (REL) network

Lymphoplasmacytic lymphoma (LPL) is usually associated with a serum IgM paraprotein, corresponding to Waldenström's Macroglobulinemia (WM). Cases presenting with IgG or IgA, or without a monoclonal protein are extremely rare. We analyzed clinical characteristics, frontline treatment, and the outcome of 45 patients with non-IgM LPL, and compared them with a control group of WM patients. The median age was similar, with significantly higher prevalence of females in non-IgM LPL, than in WM patients (60% vs 39%, P = .016). Patients with non-IgM LPL more frequently presented with lymphadenopathies (53% vs 15%, P < .001), splenomegaly (22% vs 8%, P = .015) or extranodal involvement (20% vs 8%, P = .05). In non-IgM LPL a serum monoclonal protein and bone marrow infiltration were less common than in WM patients (69% and 84% of cases respectively, P < .001 for both comparisons). The MYD88 (L265P) mutation was found in 8/19 patients using allele-specific polymerase chain reaction. A CXCR4 mutation was found in 4/17 cases using Sanger. In 16 patients we performed targeted next-generation sequencing of genes MYD88, CXCR4, ARID1-A, KMT2D, NOTCH2, TP53, PRDM1, CD79B, TRAF3, MYBBP1A, TNFAIP3. Seven patients (44%) had a MYD88 mutation (S219C in one), four (25%) a CXCR4 mutation, three (19%) a KMT2D mutation, one (6%) a TP53 mutation and one (6%) a TRAF3 mutation. With a median follow-up of 55.7 months, 36 non-IgM LPL patients (80%) were treated. Non-IgM LPL patients received more frequently anthracycline-containing regimens, as compared with WM patients, who mainly received alkylating-based therapies. Five-year overall survival (OS) was 84%, similar to that of WM patients.

Insights into the genomic landscape of MYD88 wild-type Waldenström macroglobulinemia

Activating MYD88 mutations are present in 95% of Waldenström macroglobulinemia (WM) patients, and trigger NF-κB through BTK and IRAK. The BTK inhibitor ibrutinib is active in MYD88-mutated (MYD88 ^MUT ) WM patients, but shows lower activity in MYD88 wild-type (MYD88 ^WT ) disease. MYD88 ^WT patients also show shorter overall survival, and increased risk of disease transformation in some series. The genomic basis for these findings remains to be clarified. We performed whole exome and transcriptome sequencing of sorted tumor samples from 18 MYD88 ^WT patients and compared findings with WM patients with MYD88 ^MUT disease. We identified somatic mutations predicted to activate NF-κB (TBL1XR1, PTPN13, MALT1, BCL10, NFKB2, NFKBIB, NFKBIZ, and UDRL1F), impart epigenomic dysregulation (KMT2D, KMT2C, and KDM6A), or impair DNA damage repair (TP53, ATM, and TRRAP). Predicted NF-κB activating mutations were downstream of BTK and IRAK, and many overlapped with somatic mutations found in diffuse large B-cell lymphoma. A distinctive transcriptional profile in MYD88 ^WT WM was identified, although most differentially expressed genes overlapped with MYD88 ^MUT WM consistent with the many clinical and morphological characteristics that are shared by these WM subgroups. Overall survival was adversely affected by mutations in DNA damage response in MYD88 ^WT WM patients. The findings depict genomic and transcriptional events associated with MYD88 ^WT WM and provide mechanistic insights for disease transformation, decreased ibrutinib activity, and novel drug approaches for this population.

Diagnosis of Waldenström macroglobulinemia

Waldenström macroglobulinemia is a rare disorder affecting about 1400 people annually in the United States. This case report reviews from a primary care provider's perspective the initial presentation of a patient who complained of fatigue and dizziness that ultimately led to hospital admission with a diagnosis of Waldenström macroglobulinemia. The referral to hematology/oncology prompting the bone marrow biopsy that led to the diagnosis highlights the important role of the primary care provider in the initial workup, coordination among specialists, and overall management of patients with rare disorders.

Progression Risk Stratification of Asymptomatic Waldenström Macroglobulinemia

BACKGROUND

Waldenström macroglobulinemia (WM) is preceded by asymptomatic WM (AWM), for which the risk of progression to overt disease is not well defined.

METHODS

We studied 439 patients with AWM, who were diagnosed and observed at Dana-Farber Cancer Institute between 1992 and 2014.

RESULTS

During the 23-year study period, with a median follow-up of 7.8 years, 317 patients progressed to symptomatic WM (72%). Immunoglobulin M 4,500 mg/dL or greater, bone marrow lymphoplasmacytic infiltration 70% or greater, β2-microglobulin 4.0 mg/dL or greater, and albumin 3.5 g/dL or less were all identified as independent predictors of disease progression. To assess progression risk in patients with AWM, we trained and cross-validated a proportional hazards model using bone marrow infiltration, immunoglobulin M, albumin, and beta-2 microglobulin values as continuous measures. The model divided the cohort into three distinct risk groups: a high-risk group with a median time to progression (TTP) of 1.8 years, an intermediate-risk group with a median TTP of 4.8 years, and a low-risk group with a median TTP of 9.3 years. We validated this model in two external cohorts, demonstrating robustness and generalizability. For clinical applicability, we made the model available as a Web page application ( www.awmrisk.com ). By combining two cohorts, we were powered to identify wild type MYD88 as an independent predictor of progression (hazard ratio, 2.7).

CONCLUSION

This classification system is positioned to inform patient monitoring and care and, for the first time to our knowledge, to identify patients with high-risk AWM who may need closer follow-up or benefit from early intervention.

Onsets of progression and second treatment determine survival of patients with symptomatic Waldenström macroglobulinemia

Few reports assess prognosis during follow-up of patients with symptomatic Waldenström macroglobulinemia (WM). In 121 WM patients treated between 1993 and 2016, we analyzed the prognostic role during the clinical course of the initial International Prognostic Scoring System for WM (IPSSWM). Then, we assessed onset of response, progression, and second treatment initiation coded as time-dependent covariates. High-risk IPSSWM was an adverse prognostic factor for survival after first treatment initiation (SAFTI). Nevertheless, the corresponding Dxy concordance index obtained in multiple landmark analyses decreased from 0.24 to 0.08 during the first 6 years, in accordance with a departure from the proportional hazard assumption. By contrast with onset of response (whatever its level), onset of progression and initiation of second-line treatment retained prognostic value for SAFTI (P = .02 and P = .006, respectively). These findings were confirmed in cause-specific Cox models for deaths related to WM, but not for unrelated deaths. Time to progression after first-line treatment and time to initiation of second-line treatment had no prognostic value for survival after these 2 events. These results were confirmed in an independent series of 119 patients homogeneously treated with chemoimmunotherapy. Finally, after second-line and third-line treatment, onset of progression had significant prognostic value for subsequent risk of related death only. Thus, taking initial IPSSWM and delayed response to treatment into account, only onset of progression and second treatment initiation provided additional prognostic information for SAFTI. Therefore, progression-free survival or time to next treatment may be satisfactory surrogate end points of SAFTI in WM.

Monoclonal gammopathy of clinical significance: a novel concept with therapeutic implications

Monoclonal gammopathy is a common condition, particularly in the elderly. It can indicate symptomatic multiple myeloma or another overt malignant lymphoid disorder requiring immediate chemotherapy. More frequently, it results from a small and/or quiescent secreting B-cell clone, is completely asymptomatic, and requires regular monitoring only, defining a monoclonal gammopathy of unknown significance (MGUS). Sometimes, although quiescent and not requiring any treatment per se, the clone is associated with potentially severe organ damage due to the toxicity of the monoclonal immunoglobulin or to other mechanisms. The latter situation is increasingly observed but still poorly recognized and frequently undertreated, although it often requires rapid specific intervention to preserve involved organ function. To improve early recognition and management of these small B-cell clone–related disorders, we propose to introduce the concept of monoclonal gammopathy of clinical significance (MGCS). This report identifies the spectrum of MGCSs that are classified according to mechanisms of tissue injury. It highlights the diversity of these disorders for which diagnosis and treatment are often challenging in clinical practice and require a multidisciplinary approach. Principles of management, including main diagnostic and therapeutic procedures, are also described. Importantly, efficient control of the underlying B-cell clone usually results in organ improvement. Currently, it relies mainly on chemotherapy and other anti–B-cell/plasma cell agents, which should aim at rapidly producing the best hematological response.

TP53 mutations are associated with mutated MYD88 and CXCR4, and confer an adverse outcome in Waldenström macroglobulinaemia

Little is known about TP53 mutations in Waldenström Macroglobulinaemia (WM). We evaluated 265 WM patients for TP53 mutations by next-generation sequencing, and validated the findings by Sanger sequencing. TP53 mutations were identified and validated in 6 (2·6%) patients that impacted the DNA-binding domain. All six were MYD88- and CXCR4-mutated. Ibrutinib showed activity in patients carrying all three mutations. With a median follow-up of 18 months, 2 (33%) with biallelic TP53 inactivation died of progressive disease. TP53 mutations are rare in WM, and associate with MYD88 and CXCR4 mutations. WM patients with TP53 mutations show response to ibrutinib.

A head-to-head Phase III study comparing zanubrutinib versus ibrutinib in patients with Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM), an incurable B-cell malignancy, is sensitive to Bruton tyrosine kinase (BTK) inhibition with ibrutinib, a first-generation BTK inhibitor. Off-target effects of ibrutinib against TEC- and EGFR-family kinases are implicated in some adverse events. Patients with CXCR4WHIM and MYD88L265P mutations or who are MYD88WT have less sensitivity to ibrutinib than those with MYD88L265P and CXCR4WT disease. Zanubrutinib, a next-generation BTK inhibitor with potent preclinical activity in WM and minimal off-target effects, showed sustained BTK occupancy in peripheral blood mononuclear cells from patients with B-cell malignancies and promising responses in advanced WM. Described here is a head-to-head Phase III study comparing efficacy and safety of zanubrutinib and ibrutinib in WM patients. Effect of MYD88 and CXCR4 mutation status will be assessed.

Working Toward a Genomic Prognostic Classification of Waldenström Macroglobulinemia: C-X-C Chemokine Receptor Type 4 Mutation and Beyond

Waldenström macroglobulinemia is a rare indolent B-cell lymphoma. Whole-exome sequencing studies have improved our knowledge of the Waldenström macroglobulinemia mutational landscape. The MYD88 L265P mutation is present in nearly 90% of patients with Waldenström macroglobulinemia. CXCR4 mutations are identified in approximately 30% of MYD88L265P cases and have been associated with ibrutinib resistance in clinical trials. Mutations in CD79B, ARID1a, or TP53 were described at lower frequency. Deciphering the earliest initiating lesions and identifying the molecular alterations leading to disease progression currently represent important goals in the future to identify the most relevant targets for precision therapy in Waldenström macroglobulinemia.

Initial Evaluation of the Patient with Waldenström Macroglobulinemia

The initial evaluation of the patient with Waldenström macroglobulinemia can be challenging. Not only is it a rare disease, but the clinical features can vary greatly from patient to patient. In this article, we aim at providing concise and practical recommendations for the initial evaluation of patients with Waldenström macroglobulinemia, specifically regarding history taking, physical examination, laboratory testing, bone marrow aspiration, and biopsy evaluation and imaging studies. We then review the most common special clinical situations seen in patients with Waldenström macroglobulinemia, especially anemia, hyperviscosity, cryoglobulinemia, peripheral neuropathy, extramedullary disease, Bing-Neel syndrome, and amyloidosis.

Syndrome d’hyperviscosité : mise au point pour les réanimateurs

Le syndrome d’hyperviscosité (SH) est une entité clinique composée de signes variables non spécifiques et dont le diagnostic repose sur un faisceau d’arguments contextuels, anamnestiques et clinicobiologiques. En dehors de la mesure de la viscosité plasmatique, l’examen le plus spécifique pour confirmer le diagnostic semble être le fond d’œil. L’incidence du SH est inconnue, mais il s’agit d’une complication rare d’un grand nombre de pathologies. La physiopathologie est en rapport avec une augmentation de la viscosité plasmatique ou avec une augmentation du nombre d’éléments figurés du sang et/ou une altération de la capacité de ces cellules à circuler dans le lit capillaire. Le SH relève toujours d’un traitement de la pathologie sous-jacente et d’un traitement symptomatique visant à diminuer la viscosité sanguine. Dans les formes les plus sévères, il peut être nécessaire de recourir à un traitement par aphérèse thérapeutique en urgence. Le pronostic dépend principalement de la pathologie sous-jacente.

Idelalisib in a patient with refractory Waldenström's macroglobulinemia complicated by anuric renal failure: a case report

Background

Waldenström’s macroglobulinemia is a rare B-cell lymphoma. The gold standard treatment for Waldenström’s macroglobulinemia is an anti-CD20 antibody (rituximab) in combination with alkylating agents and dexamethasone. Treatment targeting the B-cell receptor such as ibrutinib (but not idelalisib) is currently approved for treatment of patients with relapsed or refractory Waldenström’s macroglobulinemia.

Case presentation

We report a case of a 71-year-old white French man with Waldenström’s macroglobulinemia who presented with acute renal failure and hyperviscosity syndrome. His Waldenström’s macroglobulinemia was refractory to first-line treatment with rituximab, cyclophosphamide, and dexamethasone. Because of his hemorrhagic syndrome and medical history of recent myocardial infarction, we decided to treat him with idelalisib 150 mg twice daily instead of ibrutinib. We observed a very quick improvement in the patient’s clinical status without need for dose adjustment.

Conclusion

Our patient’s case provides the first evidence, to the best of our knowledge, that idelalisib may be an efficient treatment option for patients with Waldenström’s macroglobulinemia complicated by anuric renal failure and in whom ibrutinib is contraindicated.

How we manage patients with Waldenström macroglobulinaemia

Waldenström macroglobulinaemia (WM) is a rare, indolent B-cell lymphoproliferative disorder characterized by cellular involvement in bone marrow and monoclonal IgM production. Symptoms can be related to cytopenias, tumoural involvement, or IgM-related disorders. Somatic mutations in the MYD88 gene have been described in the majority of WM cases. The mutation is responsible for a gain-of-function and induces activation of nuclear factor-κB, for DNA transcription and cell survival. It seems that MYD88 mutation is associated with better prognosis and better response to some treatment. Treatments are started when WM is symptomatic, following systematic biological and morphological assessments. Therapeutic choice depends on age, frailty and urgent efficacy need. In first line, the majority of patients are treated with monoclonal anti-CD20 antibody-based regimens combined with cytotoxic chemotherapy. Rituximab, cyclophosphamide and dexamethasone remain the most commonly used regimen with good safety. Nevertheless, increasing numbers of new drugs are becoming available or are in development. Proteasome inhibitors, such as bortezomib or carfilzmib, showed good and rapid responses. Bruton tyrosine kinase (BTK) inhibitor demonstrated excellent results and is now available for relapse/refractory disease or as first line for some patients. This review highlights the diagnostic procedures and therapeutic approaches in WM.

Toward personalized treatment in Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a rare lymphoma with 1000 to 1500 new patients diagnosed per year in the United States. Patients with WM can experience prolonged survival times, which seem to have increased in the last decade, but relapse is inevitable. The identification of recurrent mutations in the MYD88 and CXCR4 genes has opened avenues of research to better understand and treat patients with WM. These developments are giving way to personalized treatment approaches for these patients, focusing on increasing depth and duration of response alongside lower toxicity rates. In the present document, we review the diagnostic differential, the clinical manifestations, and the pathological and genomic features of patients with WM. We also discuss the safety and efficacy data of alkylating agents, proteasome inhibitors, monoclonal antibodies, and Bruton tyrosine kinase inhibitors in patients with WM. Finally, we propose a genomically driven algorithm for the treatment of WM. The future of therapies for WM appears bright and hopeful, but we should be mindful of the cost-effectiveness and long-term toxicity of novel agents.

Role of IRF4 in resistance to immunomodulatory (IMid) compounds® in Waldenström's macroglobulinemia

Background

Immunomodulatory drugs, IMid compounds, are active in Waldenström's macroglobulinemia (WM), although in a lesser extent than multiple myeloma, where it was initially developed. We hypothesized WM tumour cells might develop mechanisms of resistance, and sought to identify and describe these mechanisms.

Material and Method

MM and WM-derived cell lines, and Waldenström's CD19+ cells were treated using both lenalidomide and pomalidomide. Stable CRBN expressing cells were generated.

Results

WM-derived cells were resistant to IMid compounds. We demonstrated a modulation of the downstream targets of IRF4, despite low expression of cereblon, and hypothesized IRF4 was the cause for resistance to IMid compounds. We ruled out the role of various IRF4 regulatory mechanisms, and other pathways activating WM tumor cells, such as B cell activators.

Conclusion

This study demonstrated that mechanisms of resistance to IMid compounds could be not related to cereblon. IRF4 was identified as the potential mechanism of resistance to lenalidomide and pomalidomide in WM. It potentially explains the lesser activity observed in the clinic in WM. Interestingly, some WM patients benefited strongly to lenalidomide and pomalidomide, and future studies will have to describe the indirect mechanisms of IMid compounds in WM, possibly related to an immune-mediated process.

Waldenstrom's Macroglobulinemia: A Report of Two Cases, One with Severe Retinopathy and One with Renal Failure

We report here two cases of Waldenstrom's macroglobulinemia (WM), one with central nervous system (CNS) symptoms and severe retinopathy and one with renal failure. In both cases, the serum IgM levels exceeded 3,000 mg/dL and monoclonal IgM-kappa was observed in the blood. At onset, Case 1, a 63-year-old female, developed CNS symptoms—namely, drowsiness and syncope. Case 2, a 58-year-old male, had nausea and dysgeusia on admission associated with renal failure, which is quite rare in patients with WM. Both patients exhibited hyperviscosity-related retinopathy, but it was particularly severe in Case 1: she suddenly lost her vision after admission. However, her vision recovered completely during treatment. Case 2 required hemodialysis immediately after admission. Needle biopsy of his kidney revealed tubulointerstitial nephritis with marked infiltration with CD20-positive lymphoplasmacytic lymphoma cells. After treatment, Case 1 has been in a remission longer than 8 years, but Case 2 died of pneumonia in 6 months. Since the initial symptoms of WM are ambiguous and vary significantly and hyperviscosity-related ophthalmological problems or severe renal dysfunction can arise, it is essential to promptly measure serum IgM levels and to institute appropriate care immediately when WM is confirmed in a patient.

Current applications of multiparameter flow cytometry in plasma cell disorders

Multiparameter flow cytometry (MFC) has become standard in the management of patients with plasma cell (PC) dyscrasias, and could be considered mandatory in specific areas of routine clinical practice. It plays a significant role during the differential diagnostic work-up because of its fast and conclusive readout of PC clonality, and simultaneously provides prognostic information in most monoclonal gammopathies. Recent advances in the treatment and outcomes of multiple myeloma led to the implementation of new response criteria, including minimal residual disease (MRD) status as one of the most relevant clinical endpoints with the potential to act as surrogate for survival. Recent technical progress led to the development of next-generation flow (NGF) cytometry that represents a validated, highly sensitive, cost-effective and widely available technique for standardized MRD evaluation, which also could be used for the detection of circulating tumor cells. Here we review current applications of MFC and NGF in most PC disorders including the less frequent solitary plasmocytoma, light-chain amyloidosis or Waldenström macroglobulinemia.

Serum IgM level as predictor of symptomatic hyperviscosity in patients with Waldenström macroglobulinaemia

Symptomatic hyperviscosity is a common clinical manifestation in patients with Waldenström macroglobulinaemia (WM) and high serum IgM levels. Prompt intervention is required to prevent catastrophic events, such as retinal or central nervous system bleeding. Identifying patients at high risk of symptomatic hyperviscosity might support the decision to treat asymptomatic patients before irreversible damage occurs. We carried out a large retrospective study in 825 newly diagnosed WM patients, of who 113 (14%) developed symptomatic hyperviscosity. The median serum IgM level at the time of symptomatic hyperviscosity was 61·8 g/l (range 31-124 g/l). Forty-four patients (36%) had symptomatic hyperviscosity at the time of WM diagnosis. A serum IgM level >60 g/l at diagnosis was associated with a median time to symptomatic hyperviscosity of 3 months, whereas the median time for patients with serum IgM level of 50·01-60 g/l was approximately 3 years. Adjusting for other clinical factors, the odds of developing symptomatic hyperviscosity were 370-fold higher with serum IgM levels >60 g/l, and showed an association with CXCR4 mutational status. Symptomatic hyperviscosity did not impact overall survival (P = 0·12). The findings support the use of serum IgM level >60 g/l as a criterion for initiation of therapy in an otherwise asymptomatic WM patient.