Somatic mutations in MYD88 and CXCR4 are determinants of clinical presentation and overall survival in Waldenström macroglobulinemia

Good clinical response following Ibrutinib treatment of a rare case of lymphoplasmacytic lymphoma secreting IgA kappa paraprotein: A case report

Lymphoplasmacytic lymphoma (LPL) is a malignant proliferation of small lymphocytes, lymphoplasmocytoid cells and plasmocytes affecting the bone marrow, lymph nodes and spleen. Its incidence is 1/100,000 and represents 8% of all lymphomas. A total of ~5% of patients with LPL may secrete non-IgM of IgG, IgA, kappa or lambda type or be non-secretory. In the present study, a case of a 62-year-old female patient who was diagnosed with non-IgM LPL with kappa light chain monoclonal paraprotein production and normal serum immunoglobulin levels was reported. The MYD88 L265P mutation was detected by molecular genetic analysis using a sample of the bone marrow. The patient underwent initial treatment with a combination of Bendamustine-Rituximab, and later on, Ibrutinib (a Bruton kinase inhibitor) was added to the treatment protocol. The authors' aim was to describe a case of a rare type of LPL studied and cured at the University Hospital 'St. Ivan Rilski', as well as to show the methods used for its diagnosis and their applicability. The difficulty in diagnosing such rare cases of LPL which are associated with marked plasmacytic differentiation and IgA paraprotein secretion resembling plasma cell neoplasia was addressed. From the other side, the characteristic features in favor of LPL diagnosis are the immunophenotype profile of plasmocytes, as well as the presence of MYD88 L265P mutation. Finally, the methods of management and treatment of this type of lymphoma were reported, highlighting the favorable effect of the treatment with Bruton TK inhibitor (Ibrutinib).

Clinical Validation of a Targeted Next-Generation Sequencing Panel for Lymphoid Malignancies

Lymphoid malignancies are a heterogeneous group of hematological disorders characterized by a diverse range of morphologic, immunophenotypic, and clinical features. Next-generation sequencing (NGS) is increasingly being applied to delineate the complex nature of these malignancies and identify high-value biomarkers with diagnostic, prognostic, or therapeutic benefit. However, there are various challenges in using NGS routinely to characterize lymphoid malignancies, including pre-analytic issues, such as sequencing DNA from formalin-fixed, paraffin-embedded tissue, and optimizing the bioinformatic workflow for accurate variant calling and filtering. This study reports the clinical validation of a custom capture-based NGS panel to test for molecular markers in a range of lymphoproliferative diseases and histiocytic neoplasms. The fully validated clinical assay represents an accurate and sensitive tool for detection of single-nucleotide variants and small insertion/deletion events to facilitate the characterization and management of patients with hematologic cancers specifically of lymphoid origin.

Waldenström Macroglobulinemia - A State-of-the-Art Review: Part 1: Epidemiology, Pathogenesis, Clinicopathologic Characteristics, Differential Diagnosis, Risk Stratification, and Clinical Problems

Waldenström macroglobulinemia (WM) is an infrequent variant of lymphoma, classified as a B-cell malignancy identified by the presence of IgM paraprotein, infiltration of clonal, small lymphoplasmacytic B cells in the bone marrow, and the MYD88 L265P mutation, which is observed in over 90% of cases. The direct invasion of the malignant cells into tissues like lymph nodes and spleen, along with the immune response related to IgM, can also lead to various health complications, such as cytopenias, hyperviscosity, peripheral neuropathy, amyloidosis, and Bing-Neel syndrome. Chemoimmunotherapy has historically been considered the preferred treatment for WM, wherein the combination of rituximab and nucleoside analogs, alkylating drugs, or proteasome inhibitors has exhibited notable efficacy in inhibiting tumor growth. Recent studies have provided evidence that Bruton Tyrosine Kinase inhibitors (BTKI), either used independently or in conjunction with other drugs, have been shown to be effective and safe in the treatment of WM. The disease is considered to be non-curable, with a median life expectancy of 10 to 12 years.

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.

Mutational landscape in Waldenström macroglobulinemia evaluated using a next-generation sequencing lymphoma panel in routine clinical practice

Next-generation sequencing (NGS) affords comprehensive insights into the genomic landscape of lymphomas. We examined the mutational pattern in patients with Waldenström macroglobulinemia (WM) or lymphoplasmacytic lymphoma (LPL) as well as the diagnostic and clinical utility of a tailored NGS lymphoma panel. A consecutive series of 45 patients was reviewed and NGS analysis was performed as part of a routine diagnostic setup. The custom designed NGS panel assayed all coding sequences of 59 genes of known clinical significance in lymphoid neoplasms. The most frequently mutated genes were MYD88, CXCR4, BIRC3, CD79B, and ARID1A. Additional somatic mutations were detected in 17 genes with four mutations categorized as pathogenic or likely pathogenic. BIRC3 and TP53 mutations were associated with adverse clinical phenotypes. NGS performance for the MYD88L265P variant was 96% when compared to qPCR. In conclusion, targeted NGS provided important diagnostic and prognostic information in a routine clinical setting.

The landscape of rare genetic variants in familial Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a rare hematological malignancy. Risk for WM is elevated 20-fold among first-degree relatives of patients with WM. However, the list of variants and genes that cause WM remains incomplete. In this study we analyzed exomes from 64 WM pedigrees for evidence of genetic susceptibility for this malignancy. We determined the frequency of pathogenic (P) or likely pathogenic (LP) variants among patients with WM; performed variant- and gene-level association analyses with the set of 166 WM cases and 681 unaffected controls; and examined the segregation pattern of deleterious variants among affected members in each pedigree. We identified P/LP variants in TREX1 and SAMHD1 (genes that function at the interface between innate immune response, genotoxic surveillance, and DNA repair) segregating in patients with WM from 2 pedigrees. There were additional P/LP variants in cancer-predisposing genes (eg, POT1, RECQL4, PTPN11, PMS2). In variant- and gene-level analyses, no associations were statistically significant after multiple testing correction. On a pathway level, we observed involvement of genes that play a role in telomere maintenance (q-value = 0.02), regulation of innate immune response (q-value = 0.05), and DNA repair (q-value = 0.08). Affected members of each pedigree shared multiple deleterious variants (median, n = 18), but the overlap between the families was modest. In summary, P/LP variants in highly penetrant genes constitute a modest proportion of the deleterious variants; each pedigree is largely unique in its genetic architecture, and multiple genes are likely involved in the etiology of WM.

B-cell non-Hodgkin lymphomas

B-cell lymphomas occur with an incidence of 20 new cases per 100 000 people per year in high-income countries. They can affect any organ and are characterised by heterogeneous clinical presentations and courses, varying from asymptomatic, to indolent, to very aggressive cases. Since the topic of B-cell non-Hodgkin lymphomas was last reviewed in The Lancet in 2017, a deeper understanding of the biological background of this heterogeneous group of malignancies, the availability of new diagnostic methods, and the development and implementation of new targeted and immunotherapeutic approaches have improved our ability to treat patients. This Seminar provides an overview of the pathobiology, classification, and prognostication of B-cell non-Hodgkin lymphomas and summarises the current knowledge and standard of care regarding biology and clinical management of the most common subtypes of mature B-cell non-Hodgkin lymphomas. It also highlights new findings in deciphering the molecular background of disease development and the implementation of new therapeutic approaches, particularly those targeting the immune system.

How I use genomics and BTK inhibitors in the treatment of Waldenström macroglobulinemia

ABSTRACT

Mutations in MYD88 (95%-97%) and CXCR4 (30%-40%) are common in Waldenström macroglobulinemia (WM). TP53 is altered in 20% to 30% of patients with WM, particularly those previously treated. Mutated MYD88 activates hematopoietic cell kinase that drives Bruton tyrosine kinase (BTK) prosurvival signaling. Both nonsense and frameshift CXCR4 mutations occur in WM. Nonsense variants show greater resistance to BTK inhibitors. Covalent BTK inhibitors (cBTKi) produce major responses in 70% to 80% of patients with WM. MYD88 and CXCR4 mutation status can affect time to major response, depth of response, and/or progression-free survival (PFS) in patients with WM treated with cBTKi. The cBTKi zanubrutinib shows greater response activity and/or improved PFS in patients with WM with wild-type MYD88, mutated CXCR4, or altered TP53. Risks for adverse events, including atrial fibrillation, bleeding diathesis, and neutropenia can differ based on which BTKi is used in WM. Intolerance is also common with cBTKi, and dose reduction or switchover to another cBTKi can be considered. For patients with acquired resistance to cBTKis, newer options include pirtobrutinib or venetoclax. Combinations of BTKis with chemoimmunotherapy, CXCR4, and BCL2 antagonists are discussed. Algorithms for positioning BTKis in treatment naïve or previously treated patients with WM, based on genomics, disease characteristics, and comorbidities, are presented.

Biomarker analysis of the ASPEN study comparing zanubrutinib with ibrutinib for patients with Waldenström macroglobulinemia

ABSTRACT

The phase 3 ASPEN trial (NCT03053440) compared Bruton tyrosine kinase inhibitors (BTKis), zanubrutinib and ibrutinib, in patients with Waldenström macroglobulinemia (WM). Post-hoc biomarker analysis was performed using next-generation sequencing on pretreatment bone marrow samples from 98 patients treated with zanubrutinib and 92 patients treated with ibrutinib with mutated (MUT) MYD88 and 20 patients with wild-type (WT) MYD88 treated with zanubrutinib. Of 329 mutations in 52 genes, mutations in CXCR4 (25.7%), TP53 (24.8%), ARID1A (15.7%), and TERT (9.0%) were most common. TP53MUT, ARID1AMUT, and TERTMUT were associated with higher rates of CXCR4MUT (P < .05). Patients with CXCR4MUT (frameshift or nonsense [NS] mutations) had lower very good partial response (VGPR) and complete response rates (CR; 17.0% vs 37.2%, P = .020) and longer time to response (11.1 vs 8.4 months) than patients with CXCR4WT treated with BTKis. CXCR4NS was associated with inferior progression-free survival (PFS; hazard ratio [HR], 3.39; P = .017) in patients treated with ibrutinib but not in those treated with zanubrutinib (HR, 0.67; P = .598), but VGPR + CR rates were similar between treatment groups (14.3% vs 15.4%). Compared with ibrutinib, patients with CXCR4NS treated with zanubrutinib had a favorable major response rate (MRR; 85.7% vs 53.8%; P = .09) and PFS (HR, 0.30; P = .093). In patients with TP53MUT, significantly lower MRRs were observed for patients treated with ibrutinib (63.6% vs 85.7%; P = .04) but not for those treated with zanubrutinib (80.8% vs 81.9%; P = .978). In TP53MUT, compared with ibrutinib, patients treated with zanubrutinib had higher VGPR and CR (34.6% vs 13.6%; P < .05), numerically improved MRR (80.8% vs 63.6%; P = .11), and longer PFS (not reached vs 44.2 months; HR, 0.66; P = .37). Collectively, patients with WM with CXCR4MUT or TP53MUT had worse prognosis compared with patients with WT alleles, and zanubrutinib led to better clinical outcomes.

Ibrutinib and venetoclax as primary therapy in symptomatic, treatment-naïve Waldenström macroglobulinemia

ABSTRACT

Concurrent Bruton tyrosine kinase and BCL2 inhibition has not yet been investigated in Waldenström macroglobulinemia (WM). We performed an investigator-initiated trial of ibrutinib and venetoclax in symptomatic treatment-naïve patients with MYD88-mutated WM. Patients received ibrutinib 420 mg once daily (cycle 1), followed by a ramp-up of venetoclax to 400 mg daily (cycle 2). The combination was then administered for 22 additional 4-week cycles. The attainment of very good partial response (VGPR) was the primary end point. Forty-five patients were enrolled in this study. The median baseline characteristics were as follows: age 67 years, serum IgM 43 g/L, and hemoglobin 102 g/L. Seventeen patients (38%) carried CXCR4 mutations. Nineteen patients (42%) achieved VGPR. Grade 3 or higher adverse events included neutropenia (38%), mucositis (9%), and tumor lysis syndrome (7%). Atrial fibrillation occurred in 3 (9%), and ventricular arrhythmia in 4 (9%) patients that included 2 grade 5 events. With a median follow-up of 24.4 months, the 24-month progression-free survival (PFS) and overall survival (OS) rates were 76% and 96%, respectively, and were not impacted by CXCR4 mutations. The median time on therapy was 10.2 months, and the median time after the end of therapy (EOT) was 13.3 months. Eleven of the 12 progression events occurred after EOT, and the 12-month PFS rates after EOT were 79%; 93% if VGPR was attained, and 69% for other patients (P = .12). Ibrutinib and venetoclax induced high VGPR rates and durable responses after EOT, although they were associated with a higher-than-expected rate of ventricular arrhythmia in patients with WM, leading to early study treatment termination. This trial was registered at www.clinicaltrials.gov as #NCT04273139.

Interplay between proteasome inhibitors and NF-κB pathway in leukemia and lymphoma: a comprehensive review on challenges ahead of proteasome inhibitors

The current scientific literature has extensively explored the potential role of proteasome inhibitors (PIs) in the NF-κB pathway of leukemia and lymphoma. The ubiquitin-proteasome system (UPS) is a critical component in regulating protein degradation in eukaryotic cells. PIs, such as BTZ, are used to target the 26S proteasome in hematologic malignancies, resulting in the prevention of the degradation of tumor suppressor proteins, the activation of intrinsic mitochondrial-dependent cell death, and the inhibition of the NF-κB signaling pathway. NF-κB is a transcription factor that plays a critical role in the regulation of apoptosis, cell proliferation, differentiation, inflammation, angiogenesis, and tumor migration. Despite the successful use of PIs in various hematologic malignancies, there are limitations such as resistant to these inhibitors. Some reports suggest that PIs can induce NF-κB activation, which increases the survival of malignant cells. This article discusses the various aspects of PIs' effects on the NF-κB pathway and their limitations. Video Abstract.

Single-cell analysis of MYD88L265P and MYD88WT Waldenström macroglobulinemia patients

Waldenström macroglobulinemia (WM) is characterized by the expansion of clonal lymphoplasmacytic cells; the MYD88L265P somatic mutation is found in >90% of patients, but malignant B cells may still display intra-clonal heterogeneity. To assess clonal heterogeneity in WM, we generated and performed single-cell RNA sequencing of CD19+ sorted cells from five patients with MYD88 L265P and two patients with MYD88 WT genotype as well as two healthy donors. We identified distinct transcriptional patterns in the clonal subpopulations not only between the two genetically distinct WM subgroups but also among MYD88 L265P patients, which affected the B cell composition in the different subgroups. Comparison of clonal and normal/polyclonal B cells within each patient sample enabled the identification of patient-specific transcriptional changes. We identified gene signatures active in a subset of MYD88L265P patients, while other signatures were active in MYD88 WT patients. Finally, gene expression analysis showed common transcriptional features between patients compared to the healthy control but also differentially expressed genes between MYD88 L265P and MYD88 WT patients involved in distinct pathways, including NFκΒ, BCL2, and BTK. Overall, our data highlight the intra-tumor clonal heterogeneity in WM with potential prognostic and therapeutic implications.

Waldenström Macroglobulinemia: Targeted Agents Taking Center Stage

With the worldwide approval of the oral covalent Bruton tyrosine kinase (BTK) inhibitors ibrutinib and zanubrutinib for treating patients with Waldenström macroglobulinemia (WM), targeted agents have certainly taken center stage in the therapeutic landscape of WM. This review discusses the biological and clinical data supporting current and up-and-coming targeted agents in WM. Bruton tyrosine kinase inhibitors induce fast, deep, and durable responses in patients with WM, comparable to chemoimmunotherapy; however, there is a glaring absence of comparative studies between these regimens. The high response and progression-free survival rate and the ease of administration of BTK inhibitors must be balanced against their specific adverse-event profile with unique toxicity (e.g., bleeding and cardiac arrhythmia) and the indefinite duration of the therapy. Novel targeted agents of interest include BCL2 antagonists (e.g., venetoclax and sonrotoclax) and non-covalent BTK inhibitors (e.g., pirtobrutinib and nemtabrutinib), among others. The therapeutic landscape of patients with WM will benefit from the robust participation of patients in clinical trials.

Zanubrutinib Versus Ibrutinib in Symptomatic Waldenström Macroglobulinemia: Final Analysis From the Randomized Phase III ASPEN Study

The phase III ASPEN study demonstrated the comparable efficacy and improved safety of zanubrutinib versus ibrutinib in patients with Waldenström macroglobulinemia (WM). Here, we report long-term follow-up outcomes from ASPEN. The primary end point was the sum of very good partial response (VGPR) + complete response (CR) rates; secondary and exploratory end points were also reported. Cohort 1 comprised 201 patients (myeloid differentiation primary response 88-mutant WM: 102 receiving zanubrutinib; 99 receiving ibrutinib); cohort 2 comprised 28 patients (myeloid differentiation primary response 88 wild-type WM: 28 zanubrutinib; 26 efficacy evaluable). At 44.4-month median follow-up, VGPR + CR rates were 36.3% with zanubrutinib versus 25.3% with ibrutinib in cohort 1 and 30.8% with one CR in cohort 2. In patients with CXC motif chemokine receptor 4 mutation, VGPR + CR rates were 21.2% with zanubrutinib versus 10.0% with ibrutinib (cohort 1). Median progression-free survival and overall survival were not reached. Any-grade adverse events (AEs) of diarrhea (34.7% v 22.8%), muscle spasms (28.6% v 11.9%), hypertension (25.5% v 14.9%), atrial fibrillation/flutter (23.5% v 7.9%), and pneumonia (18.4% v 5.0%) were more common with ibrutinib versus zanubrutinib; neutropenia (20.4% v 34.7%) was less common with ibrutinib versus zanubrutinib (cohort 1). Zanubrutinib was associated with lower risk of AE-related treatment discontinuation. Overall, these findings confirm the long-term response quality and tolerability associated with zanubrutinib.

Current approach to Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a unique CD20+, B-cell non-Hodgkin lymphoma, characterized by lymphoplasmacytic infiltration of the bone marrow and circulating monoclonal immunoglobulin M. The clinical manifestations and outcomes of patients are highly variable. High-level evidence supports integration of monoclonal anti-CD20 antibody, rituximab, to the chemotherapy backbone to treat WM. However, its contemporary management has become more nuanced, with deeper understanding of the pathophysiology and incorporation of Bruton's tyrosine kinase (BTK) inhibitors to the treatment paradigm. Prior knowledge of the patients' MYD88L265P and CXCR4 mutation status may aid in the treatment decision-making. Currently, the two frequently utilized approaches include fixed-duration chemoimmunotherapy and BTK inhibitor-based continuous treatment until progression. Randomized trials comparing these two vastly divergent approaches are lacking. Recent studies demonstrating efficacy of B cell lymphoma-2 (BCL2) inhibitors and non-covalent BTK inhibitors in patients, previously exposed to a covalent BTK inhibitor, are a testament to the rapidly expanding options against WM.

Clonal Relationship and Mutation Analysis in Lymphoplasmacytic Lymphoma/Waldenström Macroglobulinemia Associated With Diffuse Large B-cell Lymphoma

Patients with lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL/WM) occasionally develop diffuse large B-cell lymphoma (DLBCL). This mostly results from LPL/WM transformation, although clonally unrelated DLBCL can also arise. LPL/WM is characterized by activating MYD88L265P (>95%) and CXCR4 mutations (~30%), but the genetic drivers of transformation remain to be identified. Here, in thirteen LPL/WM patients who developed DLBCL, the clonal relationship of LPL and DLBCL together with mutations contributing to transformation were investigated. In 2 LPL/WM patients (15%), high-throughput sequencing of immunoglobulin gene rearrangements showed evidence of >1 clonal B-cell population in LPL tissue biopsies. In the majority of LPL/WM patients, DLBCL presentations were clonally related to the dominant clone in LPL, providing evidence of transformation. However, in 3 patients (23%), DLBCL was clonally unrelated to the major malignant B-cell clone in LPL, of which 2 patients developed de novo DLBCL. In this study cohort, LPL displayed MYD88L265P mutation in 8 out of eleven patients analyzed (73%), while CXCR4 mutations were observed in 6 cases (55%). MYD88WT LPL biopsies present in 3 patients (27%) were characterized by CD79B and TNFAIP3 mutations. Upon transformation, DLBCL acquired novel mutations targeting BTG1, BTG2, CD79B, CARD11, TP53, and PIM1. Together, we demonstrate variable clonal B-cell dynamics in LPL/WM patients developing DLBCL, and the occurrence of clonally unrelated DLBCL in about one-quarter of LPL/WM patients. Moreover, we identified commonly mutated genes upon DLBCL transformation, which together with preserved mutations already present in LPL characterize the mutational landscape of DLBCL occurrences in LPL/WM patients.

Zanubrutinib: past, present, and future

In recent years, Bruton tyrosine kinase (BTK) inhibitors have provided significant advances in the treatment of patients with B-cell malignancies. Ibrutinib was the first BTK inhibitor to be approved, and it changed the standard-of-care treatment for diseases such as chronic lymphocytic leukemia, mantle cell lymphoma, marginal zone lymphoma, and Waldenström macroglobulinemia, improving efficacy outcomes and safety compared to chemotherapy. In this article, we review the development of zanubrutinib, a next-generation BTK inhibitor, from molecular design to patient-related outcomes. We start this journey by providing insights into the discovery of BTK and the physiologic, genetic, and molecular characterization of patients lacking this kinase, together with the brief treatment landscape in the era of chemo-immunotherapies. Zanubrutinib was originally developed by applying a structure-activity strategy to enhance the specificity as well as enzymatic and pharmacokinetic properties. Preclinical studies confirmed greater specificity and better bioavailability of zanubrutinib compared with that of ibrutinib, which supported the initiation of clinical trials in humans. Preliminary clinical results indicated activity in B-cell malignancies together with an improved safety profile, in line with less off-target effects described in the preclinical studies. The clinical program of zanubrutinib has since expanded significantly, with ongoing studies in a wide range of hemato-oncological diseases and in combination with many other therapies. Zanubrutinib currently is approved for various B-cell malignancies in multiple countries. This story highlights the importance of multidisciplinary collaborative research, from bench to bedside, and provides an example of how the commitment to finding improved treatment options should always run parallel to patient care.

Machine learning models-based on integration of next-generation sequencing testing and tumor cell sizes improve subtype classification of mature B-cell neoplasms

Background

Next-generation sequencing (NGS) panels for mature B-cell neoplasms (MBNs) are widely applied clinically but have yet to be routinely used in a manner that is suitable for subtype differential diagnosis. This study retrospectively investigated newly diagnosed cases of MBNs from our laboratory to investigate mutation landscapes in Chinese patients with MBNs and to combine mutational information and machine learning (ML) into clinical applications for MBNs, especially for subtype classification.

Methods

Samples from the Catalogue Of Somatic Mutations In Cancer (COSMIC) database were collected for ML model construction and cases from our laboratory were used for ML model validation. Five repeats of 10-fold cross-validation Random Forest algorithm was used for ML model construction. Mutation detection was performed by NGS and tumor cell size was confirmed by cell morphology and/or flow cytometry in our laboratory.

Results

Totally 849 newly diagnosed MBN cases from our laboratory were retrospectively identified and included in mutational landscape analyses. Patterns of gene mutations in a variety of MBN subtypes were found, important to investigate tumorigenesis in MBNs. A long list of novel mutations was revealed, valuable to both functional studies and clinical applications. By combining gene mutation information revealed by NGS and ML, we established ML models that provide valuable information for MBN subtype classification. In total, 8895 cases of 8 subtypes of MBNs in the COSMIC database were collected and utilized for ML model construction, and the models were validated on the 849 MBN cases from our laboratory. A series of ML models was constructed in this study, and the most efficient model, with an accuracy of 0.87, was based on integration of NGS testing and tumor cell sizes.

Conclusions

The ML models were of great significance in the differential diagnosis of all cases and different MBN subtypes. Additionally, using NGS results to assist in subtype classification of MBNs by method of ML has positive clinical potential.

Clinical Implications of Genomic Profile in Waldenström Macroglobulinemia

With the increasing availability of sequencing techniques and new polymerase chain reaction-based methods, data regarding the genomic profile of Waldenström macroglobulinemia (WM) are being continuously analyzed and reproduced. MYD88 and CXCR4 mutations are highly prevalent in all the stages of WM, including the early IgM monoclonal gammopathy of undetermined significance or a more advanced stage, such as smoldering WM. Thus, there is a need to define genotypes before starting either standard treatment regimens or clinical trials. Here, we review the genomic profile of WM and its clinical implications while focusing on recent advances.

Biomarkers of Progression and Risk Stratification in Asymptomatic Waldenström Macroglobulinemia

Waldenström macroglobulinemia is an indolent IgM-secreting B-cell lymphoplasmacytic lymphoma that is preceded by an asymptomatic stage. Clinical and molecular features have been used in risk models to predict progression rates in different asymptomatic subgroups. Risk models used both disease-specific and nonspecific biomarkers for asymptomatic patients. Recently, models that incorporate continuous variables rather than distinct cutoffs have emerged to more accurately predict the risk of progression. Integrating genetic alterations to the clinical models is a promising approach that could improve risk stratification and management of asymptomatic patients.

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.

Highly Sensitive Detection Method of CXCR4 Tumor Hotspot Mutations by Drop-Off Droplet Digital PCR in Patients with IgM Monoclonal Gammopathies

CXCR4 mutations impact disease presentation and treatment outcomes in Waldenström macroglobulinemia. Current techniques used for CXCR4 mutation detection have a number of limitations. The aim of the present study was to develop and analytically validate a novel droplet digital PCR (ddPCR) assay for the simultaneous detection of five of the most common CXCR4 mutations in bone marrow (BM). In silico novel primers and probes designed for simultaneous detection of five hotspot mutations of CXCR4 were first performed. Experimental conditions were optimized, and the assay was analytically validated. The developed assay was further applied in 95 BM samples from patients with IgM gammopathy, 7 BM samples from patients with non-IgM gammopathy and 12 PBMCs from healthy donors, whereas a direct comparison study of Sanger sequencing and allele-specific PCR was performed by using 95 and 39 identical patient tumor DNA samples, respectively. The drop-off ddPCR assay is a robust, cost-effective, highly sensitive, and highly specific screening tool for CXCR4 mutations. Of 95 patients with IgM gammopathy samples, 27 had at least one CXCR4 mutation in their BM samples. With Sanger sequencing, 12 of the 95 samples tested positive, whereas the direct comparison of the developed assay with allele-specific PCR revealed substantial agreement. The clinical performance of the developed assay will be prospectively evaluated in a large number of patients, and the applicability of this assay will be further evaluated.

Type II Cryoglobulinemic Membranoproliferative Glomerulonephritis Caused by Mucosa-associated Lymphoid Tissue Lymphoma

A 67-year-old man complained of lower limb edema with a purpuric skin rash. Laboratory tests revealed proteinuria, elevated serum creatinine levels, and low serum albumin levels. The patient was also positive for cryoglobulin in serum, immunoglobulin (Ig) M gammopathy, hypocomplementemia, and rheumatoid factor. He was negative for anti-hepatitis C virus antibodies. A pathological analysis of the renal tissue revealed membranoproliferative glomerulonephritis, common histological features of cryoglobulinemic vasculitis (CV), and mucosa-associated lymphoid tissue lymphoma invasion. Although hematologic malignancy is a rare cause of type II CV, these clinical findings suggest that mucosa-associated lymphoid tissue lymphoma (MALT) lymphoma may have been the cause in the present case.

Monoclonal gammopathy of increasing significance: time to screen?

Monoclonal gammopathy (MG) is a frequently detected clonal B-cell or plasma-cell disorder. Importantly, every multiple myeloma (MM) case is preceded by MG. Although clinical algorithms now allow earlier treatment of patients with biomarkers of malignancy before MM-induced tissue damage (CRAB) occurs, most patients are still diagnosed late. It is important to revisit how MG should be managed in clinical practice and whether screening is required. As the prevalence of MG and other medical co-morbidities both rise with increasing age, the degree of contribution of MG to disease states other than malignant progression is often unclear. This can lead to monitoring lapses and under recognition of the organ dysfunction that can occur with monoclonal gammopathy of clinical significance (MGCS). Therefore, models of progression to MM and/or MGCS require further refinement. While MG is currently detected incidentally, a case for screening has been made with ongoing studies in this area. Screening has the potential benefit of earlier detection and prevention of both MGCS and delayed MM presentations, but important drawbacks include the psychosocial impact on individuals and resource burden on healthcare services. MG terminology should transition alongside our increasing understanding of the condition and genomic characterization that have already begun to revise the MG nomenclature. The biology of MG has been poorly understood and is often inferred from the biology of MM, which is unhelpful. We review the literature and case for MG screening in this paper. In particular, we highlight areas that require focus to establish screening for MG.

Ibrutinib in relapsed/refractory patients with Waldenström macroglobulinemia: a real-life, retrospective study on behalf of the "RTL" (regional Tuscan lymphoma network)

Ibrutinib represents the first approved treatment for patients with Waldenström macroglobulinemia (WM). There are very few published experiences outside of a clinical trial. In this study, we investigated treatment response, survival, and safety in a real life setting. We retrospectively analyzed 49 consecutive R/R WM patients, managed in 8 Tuscan onco-hematological centers, that received ibrutinib after its approval, at a maximum dose of 420 mg once per day, until disease progression or unacceptable toxicity. Median age was 65 years (range 32-86), and the median number of previous regimens was 2 (range 1-5). Overall and major response rate were 91.8% and 87.7%, respectively. At best response, median IgM level declined from 3,094 to 831 mg/dl, and Hb level increased from 10.4 to 12.7 g/dl. In an intention-to-treat analysis, 36/49 patients (73.5%) were still receiving treatment, while 13/49 (26.5%) had discontinued therapy. Six out of 49 cases (12.2%) relapsed after an initial response, and 13/49 (26.5%) had a dose reduction. Estimated 2-year PFS, DOR, and OS were 76.7%, 88.7%, and 84.1%, respectively. After a median follow-up of 18.3 months, 43/49 patients (87.8%) were alive. The most frequent AE included atrial fibrillation or flutter (6/49 cases, 12.2%), bleeding (6/49 cases, 12.2%), arthralgia/myalgia (5/49 cases, 10.2%). Ibrutinib is a suitable treatment option for R/R WM patients and also suggested by ESMO, NCCN, and other societies. PFS and OS were durable, and DOR was sustained for responsive patients. Treatment toxicity is not negligible, but manageable in most cases without treatment discontinuation.

Waldenström Macroglobulinemia and Non-IgM-Type Lymphoplasmacytic Lymphoma Are Genetically Similar

INTRODUCTION

Waldenström macroglobulinemia (WM) represents a subset of lymphoplasmacytic lymphoma (LPL) with the immunoglobulin (Ig)M paraprotein. MYD88 L265P and CXCR4 mutations are common mutations in WM patients, and mutations in ARID1A and KMT2D (MLL2) have also been reported. However, little information has been accumulated on genetic changes in LPL with other paraproteins like IgG.

METHODS

We therefore aimed to evaluate genetic differences between WM and LPL with non-IgM paraprotein (non-IgM-type LPL) using targeted next-generation sequencing (NGS) in 20 Japanese patients (10 with WM, 10 with non-IgM-type LPL).

RESULTS

Mutations were detected in ARID1A (10%), CXCR4 (20%), MYD88 (90%), and KMT2D (0%) for WM patients and in ARID1A (10%), CXCR4 (20%), MYD88 (70%), and KMT2D (10%) for non-IgM-type LPL patients. No significant differences were identified. No mutations were detected in NOTCH2, PRDM1, CD274 (PD-L1), PDCD1LG2 (PD-L2), RAG2, MYBBP1A, TP53, or CD79B.

DISCUSSION

Mutant allele frequency in MYD88 L265P did not differ significantly between WM and non-IgM-type LPL. Most mutations detected by NGS were subclonal following MYD88 L265P, although one non-IgM-type LPL patient harbored only CXCR4 S338X mutation. Our NGS analyses reveal genetic characteristics in LPL patients and suggest genetic similarities between these two subsets of LPL, WM and non-IgM-type.

Bruton tyrosine kinase inhibitors in the management of Waldenström macroglobulinemia

Bruton tyrosine kinase (BTK) inhibitors have taken a central role in the management of patients with Waldenström macroglobulinemia and are the only agents approved by the Food and Drug Administration (FDA) to treat these patients. Although associated with high rates of durable responses, unmet needs with BTK inhibitor therapy include indefinite duration therapy, high cost, scarcity of complete responses, and lower rates and shorter duration of response in patients with CXCR4 mutations. Herein, we review the data supporting the use of covalent BTK inhibitors, selected management issues, clinical trials with covalent BTK inhibitor combination regimens, and up-and-coming non-covalent BTK inhibitors.

Dose reductions in patients with Waldenström macroglobulinaemia treated with ibrutinib

Waldenström macroglobulinaemia (WM) is characterized by the presence of a MYD88^L265P mutation. This mutation promotes growth and survival of malignant cells through Bruton tyrosine kinase (BTK) activation. Ibrutinib was the first BTK inhibitor approved for WM. Intolerance to ibrutinib frequently leads to dose reductions, though the impact of reducing ibrutinib dosing has not been systematically studied. We performed a retrospective study to determine the frequency and impact of reducing ibrutinib dosing in WM patients. With a median treatment time of 64 months, 96 (27%) of 353 WM patients required a dose reduction due to adverse events such as musculoskeletal symptoms, cardiac events, dermatologic symptoms, cytopenias, and gastrointestinal symptoms. The median time to initial dose reduction was 9.3 months (range, 0.5-74). Dose reductions were more common in those 65 years of age or older versus under 65 [hazard ratio (HR) 2.46, 95% confidence interval (CI) 1.55-3.90; p < 0.001], and in females versus males (HR 2.20, 95% CI 1.41-3.28, p < 0.001). Most patients (65%) had improvement or resolution of adverse effects after initial dose reduction. With a median follow-up of three years from dose reduction, hematologic response sustained or deepened in 79% of patients. These data suggest that dose reduction of ibrutinib is a reasonable treatment approach for patients with intolerable side effects.

Treatment of relapsed and refractory Waldenstrom Macroglobulinemia

Waldenström's Macroglobulinemia (WM) is a rare type of indolent non-Hodgkin lymphoma (NHL) that remains incurable. Several effective agents such as monoclonal antibodies (in combination with chemotherapy), Bruton's tyrosine kinase inhibitors, proteasome inhibitors, and BCL2 inhibitors are (becoming) available for the treatment of relapsed and refractory WM. There is however no consensus on a preferred treatment in the relapsed setting. Choice of therapy in relapsed WM should be individualized by taking several treatment and patients characteristics into account, such as treatment duration, toxicity, age, comorbidities and MYD88^L265P and CXCR4 mutational status. Due to better understanding of WM biology and the arrival of novel anti-lymphoma agents, the therapeutic options are increasing. Non-cytotoxic and fixed duration regimens, such as those explored in other indolent NHLs should be the focus of future clinical trials in WM.

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.

[Waldenström disease: News and perspectives in 2022]

Waldenström's disease is a B-cell neoplasm characterized by the accumulation of lymphoplasmacytic cells (LPCs) in the bone marrow, and more rarely in the lymph nodes and the spleen, which produce a monoclonal immunoglobulin M (IgM) protein. The diagnosis requires the identification of LPCs in the bone marrow, using specific markers in flow cytometry. The MYD88L265P mutation is found in 95% of cases and the CXCR4 mutation in 30-40% of cases. These markers must be sought because they have a diagnostic and prognostic role, and they might become predictive in the future. The clinical presentation is very variable, and includes anomalies related to the bone marrow infiltration of the LPCs (such as anemia), but also anomalies of the physico-chemical and/or immunological activity of the overproduced IgM (hyperviscosity, AL amyloidosis, cryoglobulinemia, anti-MAG neuropathies, etc.). Prognostic scores (IPSSWM) now make it possible to understand the prognosis of symptomatic WM requiring appropriate treatment. The therapeutic management depends on many parameters, such as the specific clinical presentation, the speed of evolution and of course the age and comorbidities. Immuno-chemotherapy is often the 1st line treatment (rituximab-cyclophosphamide-dexamethasone (RCD) or bendamustine-rituximab (BR)) but the role of targeted therapies is becoming preponderant. Bruton tyrosine kinase inhibitors (BTKi) are used today in first relapse. Other therapeutic perspectives will certainly allow us tomorrow to better understand this incurable chronic disease, such as new generations of BTKi, BCL2 inhibitors, anti-CXCR4, bi-specific antibodies, and CAR-T cells.

Case report: Circulating tumor DNA technology displays temporal and spatial heterogeneity in Waldenström macroglobulinemia during treatment with BTK inhibitors

Background: Waldenström macroglobulinemia (WM) is a rare subtype of B-cell lymphoma. Rituximab-based combination therapy and Bruton's tyrosine kinase (BTK) inhibitors have greatly improved the prognosis of WM. Despite the high response rate and good tolerance of BTK inhibitors in treatment of WM, a proportion of patients still experience disease progression. Case presentation: We report a 55-year-old man with relapsed WM. The patient achieved partial remission after six courses of CHOP chemotherapy and multiple plasma exchanges in initial treatment. He was admitted to the hospital with abdominal distension, and was diagnosed with relapsed WM and subsequently started on zanubrutinib. Disease progression and histological transformation occurred during treatment. We performed liquid biopsies on transformed plasma, tumor tissue and ascites at the same time and found high consistency between ascites and tissues. Moreover, we detected resistance mutations of BTK inhibitors (BTK, PLCG2) in ascites that were not detected in plasma or tissue. Eventually, the patient died during the 15-month follow-up after relapse. Conclusion: We describe a rare case of WM transformation to DLCBCL treated with chemoimmunotherapy and BTK inhibition. We analyzed tumor DNA obtained at different anatomic sites and circulating tumor DNA (ctDNA) derived from plasma and ascites specimens, with apparent significant temporal and spatial heterogeneity. The case specifically highlights the clinical value of ctDNA of ascites supernatant from WM patients, which is a more convenient and relatively noninvasive method compared with traditional invasive tissue biopsy.

MYD88 L265P Mutation Detection by ddPCR: Recommendations for Screening and Minimal Residual Disease Monitoring : ddPCR for Highly Sensitive Detection of MYD88 L265P Mutation

MYD88^L265P is a gain-of-function mutation, arising from the missense alteration c.794T>C, that frequently occurs in B-cell malignancies such as Waldenstrom macroglobulinemia and less frequently in IgM monoclonal gammopathy of undetermined significance (IgM-MGUS) or other lymphomas. MYD88^L265P has been recognized as a relevant diagnostic flag, but also as a valid prognostic and predictive biomarker, as well as an investigated therapeutic target. Up until now, allele-specific quantitative PCR (ASqPCR) has been widely used for MYD88^L265P detection providing a higher level of sensitivity than Sanger sequencing. However, the recently developed droplet digital PCR (ddPCR) shows a deeper sensitivity, compared to ASqPCR, that is necessary for screening low infiltrated samples. Actually, ddPCR could represent an improvement in daily laboratory practice since it allows mutation detection in unselected tumor cells, allowing to bypass the time-consuming and costly B-cell selection procedure. ddPCR accuracy has been recently proved to be suitable also for mutation detection in "liquid biopsy" samples that might be used as a noninvasive and patient-friendly alternative to bone marrow aspiration especially during the disease monitoring. The relevance of MYD88^L265P, both in daily management of patients and in prospective clinical trials investigating the efficacy of novel agents, makes crucial to find a sensitive, accurate, and reliable molecular technique for mutation detection. Here, we propose a protocol for MYD88^L265P detection by ddPCR.

A comparison of the International Consensus and 5th World Health Organization classifications of mature B-cell lymphomas

Several editions of the World Health Organization (WHO) classifications of lympho-hemopoietic neoplasms in 2001, 2008 and 2017 served as the international standard for diagnosis. Since the 4th WHO edition, here referred as WHO-HAEM4, significant clinico-pathological, immunophenotypic and molecular advances have been made in the field of lymphomas, contributing to refining diagnostic criteria of several diseases, to upgrade entities previously defined as provisional and to identify new entities. This process has resulted in two recent classifying proposals of lymphoid neoplasms, the International Consensus Classification (ICC) and the 5th edition of the WHO classification (WHO-HAEM5). In this paper, we review and compare the two classifications in terms of diagnostic criteria and entity definition, with focus on mature B-cell neoplasms. The main aim is to provide a tool to facilitate the work of pathologists, hematologists and researchers involved in the diagnosis and treatment of lymphomas.

Genomic profiling for clinical decision making in lymphoid neoplasms

With the introduction of large-scale molecular profiling methods and high-throughput sequencing technologies, the genomic features of most lymphoid neoplasms have been characterized at an unprecedented scale. Although the principles for the classification and diagnosis of these disorders, founded on a multidimensional definition of disease entities, have been consolidated over the past 25 years, novel genomic data have markedly enhanced our understanding of lymphomagenesis and enriched the description of disease entities at the molecular level. Yet, the current diagnosis of lymphoid tumors is largely based on morphological assessment and immunophenotyping, with only few entities being defined by genomic criteria. This paper, which accompanies the International Consensus Classification of mature lymphoid neoplasms, will address how established assays and newly developed technologies for molecular testing already complement clinical diagnoses and provide a novel lens on disease classification. More specifically, their contributions to diagnosis refinement, risk stratification, and therapy prediction will be considered for the main categories of lymphoid neoplasms. The potential of whole-genome sequencing, circulating tumor DNA analyses, single-cell analyses, and epigenetic profiling will be discussed because these will likely become important future tools for implementing precision medicine approaches in clinical decision making for patients with lymphoid malignancies.

First-Line Treatment of Waldenström’s Macroglobulinaemia: Considerations Based on the Dutch National Guideline

Waldenström macroglobulinemia (WM) is a rare B-cell Non-Hodgkin Lymphoma. There are only few prospective randomized clinical trials to guide treatment recommendations and there is no international consensus on a preferred first line treatment approach. In the recently revised Dutch guideline for WM, we describe recommendations for practice based as much as possible on the known data. Here, we summarize the considerations for first-line treatment based on these Dutch guidelines. Available evidence is summarized, including efficacy and toxicity data. Combinations of Rituximab with chemotherapy, proteasome inhibition or BTK-inhibition are all valid first line treatment options. The Dutch WM working group considers Dexamethasone/Rituximab/Cylofosfamide (DRC) a suitable first-line treatment for many WM patients, given the efficacy, the relatively mild toxicity profile and the extensive experience with this regimen. However, the long-term toxicities of DRC are unclear and need further clarification. Other regimens such as R-bendamustine, R-Bortezomib-dexamethason are also effective options, however with specific toxicities. BTK-inhibitors are not a preferred option in first line for most patients in the Dutch WM guidelines because of the need for longterm treatment and toxicities. Based on patient preferences research, future clinical trials should focus on effective fixed-duration regimens with non-cytotoxic therapies that have a favorable toxicity profile. Further development of (combinations with) BCL-2 inhibititors, novel proteasome inhibitors and BTK-inhibition could be interesting. In addition T-cell-directed treatments including bispecific antibodies as a monotherapy or combined with other novel agents deserve further study in WM.

Should Patients with Waldenström Macroglobulinemia Receive a BTK Inhibitor as Frontline Therapy?

Waldenström Macroglobulinemia (WM) is a rare indolent lymphoma with heterogeneous clinical presentation. As there are no randomised trials suggesting the best treatment option in treatment-naive patients, guidelines suggest either rituximab-combining regimens or BTK-inhibitors (BTKi) as feasible alternatives. Several factors play in the decision-making process: patients’ age and fitness, disease characteristics and genotype. Chemoimmunotherapy (CIT) represents a fixed-duration, less expensive and effective option, able to achieve prolonged time-to-next treatment even in patients with unfavourable genotypes. Immunosuppression and treatment-related second cancers may represent serious concerns. Proteasome-inhibitor-based regimens are effective with rapid disease control, although bortezomib-related neuropathy discourages the choice of these agents and treatment schedules may not be easily manageable in the elderly. BTKi have demonstrated high rates of response and prolonged survival together with the convenience of an oral administration and limited cytopenias. However, outcomes are impacted by genotype and some concerns remain, in particular the continuous drug exposure that may result in extra-haematological complications and drug resistance. Although next-generation BTKi have improved treatment tolerance, the question whether BTKi should be offered as frontline therapy to every patient is still debated. Giving fixed-duration schedule, prolonged time-to-next treatment and outcomes independent of genotype, CIT is still our preferred choice in WM. However, BTKi remain a valuable option in frail patients unsuitable for CIT.

Evaluation of orelabrutinib monotherapy in patients with relapsed or refractory Waldenström's macroglobulinemia in a single-arm, multicenter, open-label, phase 2 study

Background

Orelabrutinib is a novel, small molecule, selective irreversible Bruton tyrosine kinase inhibitor. The purpose of this study was to evaluate the efficacy and safety of orelabrutinib in patients with relapsed or refractory Waldenström's macroglobulinemia (R/R WM).

Methods

This is a prospective, multicenter study of orelabrutinib in patients with WM who had at least one prior line of treatment. Orelabrutinib was administered orally at a daily dose of 150 mg until disease progression or unacceptable toxicity. The primary endpoint was major response rate (MRR) assessed by the Independent Review Committee (IRC) according to IWWM-6. This study is registered with ClinicalTrials.gov, NCT04440059. This trial was also registered on Center for Drug Evaluation (www.chinadrugtrials.org.cn) in March 2019, with a number of CTR2019036.

Findings

Between August 2019 and December 2020, 66 R/R WM patients were assessed for eligibility. Forty-seven eligible patients were evaluated for efficacy at a median follow-up of 16.4 months (interquartile range: 12.5, 19.5). As assessed by IRC, the MRR was 80.9%, and the overall response rate was 89.4%. The median time to at least a minor response was 1.9 months. The PFS rates was 89.4% at 12 months. For patients with MYD88L265P /CXCR4NEG, MYD88L265P /CXCR4 S338X, and MYD88NEG /CXCR4NEG mutations, the MRRs were 84.6%, 100%, and 25.0%. Most adverse events were Grades 1 or 2 (91.0%). The common grade 3 or higher adverse events occurring were neutropenia (10.6%), thrombocytopenia (6.4%), and pneumonia (4.3%). Serious adverse events (SAE) occurred in 10 patients (21.3%). One treatment-related death was reported (hepatitis B reactivation).

Interpretation

Orelabrutinib has shown good efficacy and manageable safety profiles in patients with R/R WM.

Funding

InnoCare Pharma.

The Spectrum of Ocular Manifestations in Patients with Waldenström's Macroglobulinemia

PURPOSE

To investigate the ocular manifestations in 91 Waldenström's macroglobulinemia (WM) patients.

METHODS

Retrospective, cross-sectional, observational analysis.

RESULTS

Ocular impairments, detected in 19 patients, included flame-shaped hemorrhages, venous sausaging, papilledema, macular detachments, or central retinal vein occlusion in 16 patients; paraproteinemic keratopathy in 2; and a CANOMAD syndrome in 1. Best-corrected visual acuity was ≥0.5 logMAR units in 11 of 38 eyes. Intraocular pressure was increased in seven eyes. Genetic analysis in seven patients showed a mutation in the MYD88 gene in six patients and a nonsense mutation in the CXCR4 gene in five patients. Plasmapheresis followed by chemotherapy with or without the addition of rituximab resulted in improvement or normalization of the ophthalmological findings in 15 patients.

CONCLUSION

The ocular manifestations of WM are protean and potentially sight threatening. Recent advances in genomic profiling and chemotherapy have remarkably improved the hematological and ophthalmological outcomes of these patients.

A Canadian Perspective on the Treatment of Waldenström Macroglobulinemia

Waldenström macroglobulinemia (WM) is a slowly progressing B-cell non-Hodgkin lymphoma characterized by monoclonal IgM gammopathy in the blood and infiltration of the bone marrow by clonal lymphoplasmacytic cells. As an incurable disease, the goals for therapy for WM are to relieve symptoms, slow disease progression, prevent organ damage, and maintain quality of life. However, given the rarity of WM, clinical trials comparing treatments for WM are limited and there is no definitive standard of care. The selection of first-line WM therapy is thus based on patient factors, disease characteristics, and drug access, with bendamustine-rituximab and Bruton's tyrosine kinase (BTK) inhibitor therapy considered preferred treatments. Other treatments such as proteasome inhibitor- or purine analogue-based therapy, alternative chemoimmunotherapy, and autologous stem cell transplantation are generally reserved for the relapsed setting but may be used in rare circumstances in earlier lines of therapy. This paper summarizes the efficacy and safety of these WM therapies and discusses considerations for treatment from a Canadian perspective.

SOHO State of the Art Updates and Next Questions: Targeted therapies and emerging novel treatment approaches for Waldenström Macroglobulinemia

Waldenström Macroglobulinemia (WM) is a rare hematologic malignancy characterized by the presence of lymphoplasmacytic lymphoma cells involving the bone marrow and production of a monoclonal IgM paraprotein. Recurrent somatic mutations in MYD88^L265P and CXCR4 have been reported in 90% to 95% and 30% to 40% of patients with WM, respectively. Standard treatment regimens combine the anti-CD20 antibody rituximab with alkylating agents (eg, bendamustine, cyclophosphamide), nucleoside analogs (eg, fludarabine, cladribine), or proteasome inhibitors (eg, bortezomib, carfilzomib, and ixazomib). Covalent BTK inhibitors (eg, ibrutinib, acalabrutinib, zanubrutinib) have shown to be safe and highly effective in patients with WM. Novel and promising agents in this disease include next-generation covalent BTK inhibitors (eg, tirabrutinib, orelabrutinib), non-covalent BTK inhibitors (eg, pirtobrutinib, ARQ531), BCL-2 antagonists (eg, venetoclax), and CXCR4-targeted agents (eg, mavorixafor, ulocuplumab), among others. Future studies will focus on developing fixed-duration combinations regimens with these novel agents aimed at increasing durable responses while minimizing toxicity and cost.

Treatment and Survival Outcomes of Waldenstrom Macroglobulinemia in Latin American Patients: A Multinational Retrospective Cohort Study

Waldenstrom Macroglobulinemia (WM) is a rare lymphoma with distinct clinical features, and data from Latin American patients are lacking. Therefore, we aim to investigate the clinical, therapy, and outcome patterns of WM in Latin America.

Waldenstrom Macroglobulinemia (WM) is a rare lymphoma with distinct clinical features. Data from Latin American WM patients are lacking. In this article, we report, for the first time, the results of a retrospective analysis focused on the clinical, therapy, and outcome patterns of WM in Latin America. Moreover, we have validated the IPSSWM score as a prognostic factor for mortality and disease progression. Despite the limitations we acknowledge, this is the first study to provide novel real-world data on WM in Latin America.

The 5th edition of the World Health Organization Classification of Haematolymphoid Tumours: Lymphoid Neoplasms

We herein present an overview of the upcoming 5^th edition of the World Health Organization Classification of Haematolymphoid Tumours focussing on lymphoid neoplasms. Myeloid and histiocytic neoplasms will be presented in a separate accompanying article. Besides listing the entities of the classification, we highlight and explain changes from the revised 4^th edition. These include reorganization of entities by a hierarchical system as is adopted throughout the 5^th edition of the WHO classification of tumours of all organ systems, modification of nomenclature for some entities, revision of diagnostic criteria or subtypes, deletion of certain entities, and introduction of new entities, as well as inclusion of tumour-like lesions, mesenchymal lesions specific to lymph node and spleen, and germline predisposition syndromes associated with the lymphoid neoplasms.

SOHO State of the Art Updates and Next Questions: Waldenström Macroglobulinemia - 2021 Update on Management and Future Directions

Waldenstrom macroglobulinemia (WM) is a low-grade B-cell lymphoproliferative disorder. It is defined by having ≥ 10% bone marrow infiltration with lymphoplasmacytic cells and/or an immunoglobulin M (IgM) monoclonal gammopathy of ≥3g/dL. Risk factors include a personal history of IgM MGUS, and a family history of WM or a related disorder. Race, sex, and chronic antigen stimulation also appear to influence risk. Between 93 to 97% of patients with WM have a somatic mutation of the MYD88 gene. Of these, approximately 30% also have a mutation of CXCR4. The presence of a MYD88 mutation is associated with higher 10-year overall survival (90% vs. 73%; P < .001), while CXCR4 mutation status does not appear to have a similar effect. Based on consensus guidelines, WM patients with a disease-related hemoglobin level of less than 10g/dL, a platelet count of less than 100×10 9/L, bulky adenopathy or organomegaly, symptomatic hyperviscosity, severe neuropathy, amyloidosis, cryoglobulinemia, cold agglutinin disease, or evidence of disease transformation, should be considered for immediate therapy. Patients not meeting these criteria may be observed, with monitoring at 3 to 6 month intervals. When treatment is warranted, combinations of rituximab with alkylating agents and proteasome inhibitors are often effective, as are Bruton's tyrosine kinase (BTK) inhibitors and BCL-2 inhibitors. Selection among available regimens should take patients' gene mutation profile, disease-related features, and co-morbid conditions into account. Promising novel therapies in development include non-covalent BTK inhibitors, CXCR4 antagonists, BCL 2 inhibitors, bi-specific antibodies, radioimmunoconjugates, and CD19- and CD20-Targeted Chimeric Antigen Receptor T cells.

MYD88 Mutations: Transforming the Landscape of IgM Monoclonal Gammopathies

The MYD88 gene has a physiological role in the innate immune system. Somatic mutations in MYD88, including the most common L265P, have been associated with the development of certain types of lymphoma. MYD88L265P is present in more than 90% of patients with Waldenström's macroglobulinemia (WM) and IgM monoclonal gammopathy of undetermined significance (IgM-MGUS). The absence of MYD88 mutations in WM patients has been associated with a higher risk of transformation into aggressive lymphoma, resistance to certain therapies (BTK inhibitors), and shorter overall survival. The MyD88 signaling pathway has also been used as a target for specific therapies. In this review, we summarize the clinical applications of MYD88 testing in the diagnosis, prognosis, follow-up, and treatment of patients. Although MYD88L265P is not specific to WM, few tumors present a single causative mutation in a recurrent position. The role of the oncogene in the pathogenesis of WM is still unclear, especially considering that the mutation can be found in normal B cells of patients, as recently reported. This may have important implications for early lymphoma detection in healthy elderly individuals and for the treatment response assessment based on a MYD88L265P analysis.

Mast cell density and its clinical relevance in Waldenström's macroglobulinemia

The presence of numerous mast cells (MCs) mixed with tumor cells in the bone marrow (BM) is a hallmark of the diagnosis of Waldenström's macroglobulinemia (WM). MCs have been shown to support lymphoplasmacytic cell growth, but there is thus far no demonstration of the prognostic impact of BM MC density in WM. We investigated BM MC density by sensitive and specific digital quantification, allowing the analysis of a large area infiltrated by BM tumor cells. A total of 65 WM patients were investigated, including 54 at diagnosis and 11 at relapse. Tryptase and CD20 immunohistochemisty staining was performed on contiguous sections of deparaffinized BM trephine biopsies. After numerization of each section, the BM surface area was manually marked out, excluding the bone framework and adipocytes to limit the analyses to only hematopoietic tissue. MCs were assessed using a digital tool previously used to quantify immune-cell infiltrates on tumor-tissue sections. Deep next-generation sequencing and allele-specific PCR were used to explore the MYD88 and CXCR4 mutational status. MC density was heterogeneous among the WM patients. An optimal MC density threshold (> 56 MC.mm-2) was defined according to ROC curve analysis of overall survival. A higher MC density (> 56 MC.mm-2) was associated with greater BM involvement by WM lymphoplasmacytic cells and less hepatosplenic involvement (p = 0.023). Furthermore, MC density significantly correlated with a higher ISSWM score (p = 0.0003) in symptomatic patients. Patients with a higher MC density showed shorter median OS (56.5 months vs. nonreached, p = 0.0004), even in multivariate analysis after controlling for other predictive variables, such as age, ISSWM score, and CXCR4 mutational status. In conclusion, MC density can be accurately measured in WM patients using a specific digital tool on well-outlined hematopoietic tissue surfaces. High MC density is associated with aggressive features and a poor clinical outcome, emphasizing the need for further investigation of the involvement of MCs in the pathophysiology of WM.

Treatment paradigm in Waldenström macroglobulinemia: frontline therapy and beyond

Waldenström macroglobulinemia (WM) is an indolent lymphoplasmacytic lymphoma. Recent strides made in the genomic profiling of patients with WM have led to the identification of many novel therapeutic targets. Patients with WM can present with asymptomatic disease and not all patients require treatment. When criteria for initiating systemic therapy are met, the choice of therapy depends on the tumor genotype (MYD88 and CXCR4 mutation status), patient preference (fixed versus continuous duration therapy, oral versus intravenous route, cost), associated medical comorbidities, and adverse effect profile of the treatment. In the absence of head-to-head comparison between chemoimmunotherapy and Bruton’s tyrosine kinase inhibitors in otherwise fit patients with a MYD88^L265P mutation, our preference is fixed duration therapy with four to six cycles of chemoimmunotherapy with bendamustine–rituximab. In this review, we discuss the role of MYD88 and CXCR4 mutation in treatment selection, and current data for frontline and salvage treatment options in patients with WM.