ASXL1 mutations are associated with a response to alvocidib and 5-azacytidine combination in myelodysplastic neoplasms

Inhibitors of anti-apoptotic BCL-2 family proteins in combination with chemotherapy and hypomethylating agents (HMA) are promising therapeutic approaches in acute myeloid leukemia (AML) and high-risk myelodysplastic syndromes (MDS). Alvocidib, a cyclin-dependent kinase 9 (CDK9) inhibitor and indirect transcriptional repressor of the anti-apoptotic factor MCL-1, has previously shown clinical activity in AML. Availability of biomarkers for response to the alvocidib + 5-azacytidine (5-AZA) could also extend the rationale of this treatment concept to high-risk MDS. In this study, we performed a comprehensive in vitro assessment of alvocidib and 5-AZA effects in N=45 high-risk MDS patients. Our data revealed additive cytotoxic effects of the combination treatment. Mutational profiling of MDS samples identified ASXL1 mutations as predictors of response. Further, increased response rates were associated with higher gene expression of the pro-apoptotic factor NOXA in ASXL1-mutated samples. The higher sensitivity of ASXL1 mutant cells to the combination treatment was confirmed in vivo in ASXL1Y588X transgenic mice. Overall, our study demonstrated augmented activity for the alvocidib + 5-AZA combination in higher-risk MDS and identified ASXL1 mutations as a biomarker of response for potential stratification studies.

Prevalence of hypersensitivity reactions in various forms of mastocytosis: A pilot study of 2485 adult patients with mastocytosis collected in the ECNM registry

BACKGROUND

Hypersensitivity reactions (HR) are common in mastocytosis. However, little is known about triggers and risk factors. The registry of the European Competence Network on Mastocytosis (ECNM) enables reliable studies in a larger cohort of mastocytosis patients. We assessed prevalence, triggers and risk factors of HR in adults with mastocytosis in the ECNM registry.

METHODS

Data were collected in 27 ECNM centers. We analyzed potential triggers (Hymenoptera venoms, food, drug, inhalant and others) and risk factors at diagnosis and during follow-up. The study group consisted of 2485 adults with mastocytosis, 1379 women (55.5%) and 1106 men (44.5%). Median age was 48.2 years (range 18-91 years).

RESULTS

Nine hundred and forty eight patients (38.1%) reported one or more HR`. Most common triggers were Hymenoptera venoms in cutaneous mastocytosis (CM) and indolent systemic mastocytosis (ISM), whereas in advanced SM (advSM), most common elicitors were drugs, including nonsteroidal anti-inflammatory agents and penicillin. In multivariate analyses, tryptase level < 90 ng/mL, <15% infiltration by mast cells in bone marrow biopsy-sections, and diagnosis of ISM were identified as independent risk factors for HR. For drug-induced HR, prominent risk factors were advSM and high tryptase levels. New reactions were observed in 4.8% of all patients during 4 years follow-up.

CONCLUSIONS

HR are mainly triggered by Hymenoptera venoms in patients with CM and ISM and by drugs in patients with advSM. Tryptase levels <90 ng/mL, mast cell bone marrow infiltration <15%, and WHO category ISM are predictors of HR. New HR occur in 4.8% of all patients within 4 years.

Tumor necrosis factor α promotes clonal dominance of KIT D816V+ cells in mastocytosis: role of survivin and impact on prognosis

ABSTRACT

Systemic mastocytosis (SM) is defined by the expansion and accumulation of neoplastic mast cells (MCs) in the bone marrow (BM) and extracutaneous organs. Most patients harbor a somatic KIT D816V mutation, which leads to growth factor-independent KIT activation and accumulation of MC. Tumor necrosis factor α (TNF) is a proapoptotic and inflammatory cytokine that has been implicated in the clonal selection of neoplastic cells. We found that KIT D816V increases the expression and secretion of TNF. TNF expression in neoplastic MCs is reduced by KIT-targeting drugs. Similarly, knockdown of KIT or targeting the downstream signaling cascade of MAPK and NF-κB signaling reduced TNF expression levels. TNF reduces colony formation in human BM cells, whereas KIT D816V+ cells are less susceptible to the cytokine, potentially contributing to clonal selection. In line, knockout of TNF in neoplastic MC prolonged survival and reduced myelosuppression in a murine xenotransplantation model. Mechanistic studies revealed that the relative resistance of KIT D816V+ cells to TNF is mediated by the apoptosis-regulator BIRC5 (survivin). Expression of BIRC5 in neoplastic MC was confirmed by immunohistochemistry of samples from patients with SM. TNF serum levels are significantly elevated in patients with SM and high TNF levels were identified as a biomarker associated with inferior survival. We here characterized TNF as a KIT D816V-dependent cytokine that promotes clonal dominance. We propose TNF and apoptosis-associated proteins as potential therapeutic targets in SM.

Significant improvement of bone marrow-derived MSC expansion from MDS patients by defined xeno-free medium

BACKGROUND

Robust and reliable in vitro and in vivo models of primary cells are necessary to study the pathomechanisms of Myelodysplastic Neoplasms (MDS) and identify novel therapeutic strategies. MDS-derived hematopoietic stem and progenitor cells (HSPCs) are reliant on the support of bone marrow (BM) derived mesenchymal stroma cells (MSCs). Therefore, isolation and expansion of MCSs are essential for successfully modeling this disease. For the clinical use of healthy MSCs isolated from human BM, umbilical cord blood or adipose tissue, several studies showed that xeno-free (XF) culture conditions resulted in superior growth kinetics compared to MSCs cultured in the presence of fetal bovine serum (FBS). In this present study, we investigate, whether the replacement of a commercially available MSC expansion medium containing FBS with a XF medium is beneficial for the expansion of MSCs derived from BM of MDS patients which are often difficult to cultivate.

METHODS

MSCs isolated from BM of MDS patients were cultured and expanded in MSC expansion medium with FBS or XF supplement. Subsequently, the impact of culture media on growth kinetics, morphology, immunophenotype, clonogenic potential, differentiation capacity, gene expression profiles and ability to engraft in immunodeficient mouse models was evaluated.

RESULTS

Significant higher cell numbers with an increase in clonogenic potential were observed during culture of MDS MSCs with XF medium compared to medium containing FBS. Differential gene expression showed an increase in transcripts associated with MSC stemness after expansion with XF. Furthermore, immunophenotypes of the MSCs and their ability to differentiate into osteoblasts, adipocytes or chondroblasts remained stable. MSCs expanded with XF media were similarly supportive for creating MDS xenografts in vivo as MSCs expanded with FBS.

CONCLUSION

Our data indicate that with XF media, higher cell numbers of MDS MSCs can be obtained with overall improved characteristics in in vitro and in vivo experimental models.

Mast cell leukemia: clinical and molecular features and survival outcomes of patients in the ECNM Registry

Mast cell leukemia (MCL) is a rare subtype of systemic mastocytosis defined by ≥20% mast cells (MC) on a bone marrow aspirate. We evaluated 92 patients with MCL from the European Competence Network on Mastocytosis registry. Thirty-one (34%) patients had a diagnosis of MCL with an associated hematologic neoplasm (MCL-AHN). Chronic MCL (lack of C-findings) comprised 14% of patients, and only 4.5% had "leukemic MCL" (≥10% circulating MCs). KIT D816V was found in 62/85 (73%) evaluable patients; 9 (11%) individuals exhibited alternative KIT mutations, and no KIT variants were detected in 14 (17%) subjects. Ten evaluable patients (17%) had an abnormal karyotype and the poor-risk SRSF2, ASXL1, and RUNX1 (S/A/R) mutations were identified in 16/36 (44%) patients who underwent next-generation sequencing. Midostaurin was the most common therapy administered to 65% of patients and 45% as first-line therapy. The median overall survival (OS) was 1.6 years. In multivariate analysis (S/A/R mutations excluded owing to low event rates), a diagnosis of MCL-AHN (hazard ratio [HR], 4.7; 95% confidence interval [CI], 1.7-13.0; P = .001) and abnormal karyotype (HR, 5.6; 95% CI, 1.4-13.3; P = .02) were associated with inferior OS; KIT D816V positivity (HR, 0.33; 95% CI, 0.11-0.98; P = .04) and midostaurin treatment (HR, 0.32; 95% CI, 0.08-0.72; P = .008) were associated with superior OS. These data provide the most comprehensive snapshot of the clinicopathologic, molecular, and treatment landscape of MCL to date, and should help further inform subtyping and prognostication of MCL.

Inhibition of lysyl oxidases synergizes with 5-azacytidine to restore erythropoiesis in myelodysplastic and myeloid malignancies

Limited response rates and frequent relapses during standard of care with hypomethylating agents in myelodysplastic neoplasms (MN) require urgent improvement of this treatment indication. Here, by combining 5-azacytidine (5-AZA) with the pan-lysyl oxidase inhibitor PXS-5505, we demonstrate superior restoration of erythroid differentiation in hematopoietic stem and progenitor cells (HSPCs) of MN patients in 20/31 cases (65%) versus 9/31 cases (29%) treated with 5-AZA alone. This effect requires direct contact of HSPCs with bone marrow stroma components and is dependent on integrin signaling. We further confirm these results in vivo using a bone marrow niche-dependent MN xenograft model in female NSG mice, in which we additionally demonstrate an enforced reduction of dominant clones as well as significant attenuation of disease expansion and normalization of spleen sizes. Overall, these results lay out a strong pre-clinical rationale for efficacy of combination treatment of 5-AZA with PXS-5505 especially for anemic MN.

Prognostic Impact of Organomegaly in Mastocytosis: An Analysis of the European Competence Network on Mastocytosis

BACKGROUND

Organomegaly, including splenomegaly, hepatomegaly, and/or lymphadenopathy, are important diagnostic and prognostic features in patients with cutaneous mastocytosis (CM) or systemic mastocytosis (SM).

OBJECTIVES

To investigate the prevalence and prognostic impact of 1 or more organomegalies on clinical course and survival in patients with CM/SM.

METHODS

Therefore, 3155 patients with CM (n = 1002 [32%]) or SM (n = 2153 [68%]) enrolled within the registry of the European Competence Network on Mastocytosis were analyzed.

RESULTS

Overall survival (OS) was adversely affected by the number of organomegalies (OS: #0 vs #1 hazard ratio [HR], 4.9; 95% CI, 3.4-7.1, P < .001; #1 vs #2 HR, 2.1, 95% CI, 1.4-3.1, P < .001; #2 vs #3 HR, 1.7, 95% CI, 1.2-2.5, P = .004). Lymphadenopathy was frequently detected in patients with smoldering SM (SSM, 18 of 60 [30%]) or advanced SM (AdvSM, 137 of 344 [40%]). Its presence confered an inferior outcome in patients with AdvSM compared with patients with AdvSM without lymphadenopathy (median OS, 3.8 vs 2.6 years; HR, 1.6; 95% CI, 1.2-2.2; P = .003). OS was not different between patients having organomegaly with either ISM or SSM (median, 25.5 years vs not reached; P = .435). At time of disease progression, a new occurrence of any organomegaly was observed in 17 of 40 (43%) patients with ISM, 4 of 10 (40%) patients with SSM, and 33 of 86 (38%) patients with AdvSM, respectively.

CONCLUSIONS

Organomegalies including lymphadenopathy are often found in SSM and AdvSM. ISM with organomegaly has a similar course and prognosis compared with SSM. The number of organomegalies is adversely associated with OS. A new occurrence of organomegaly in all variants of SM may indicate disease progression.

Global Classification of Mast Cell Activation Disorders: An ICD-10-CM-Adjusted Proposal of the ECNM-AIM Consortium

Mast cell activation (MCA) is common and occurs in a number of pathologic conditions, including IgE-dependent and independent allergic reactions, atopic disorders, autoimmune processes, and mastocytosis. In a subset of patients, no underlying disease and no known trigger of MCA are found. When the symptoms are severe, systemic, and recurrent, and accompanied by a diagnostic increase in the serum tryptase level or other mast cell mediators, an MCA syndrome (MCAS) may be diagnosed. In these patients, the symptoms typically respond to drugs suppressing MCA, mediator production in mast cells, or mediator effects. In each case, diagnostic consensus criteria must be fulfilled to diagnose MCAS. In other patients, MCA may be local, less severe, or less acute, or may be suspected but not confirmed, so that the diagnostic criteria of MCAS are not fulfilled. In these patients, it may be difficult to prove MCA, for example, by measuring multiple mast cell mediators or basophil activation, the latter as a surrogate of IgE-dependent hypersensitivity. However, validated diagnostic criteria for implicating suspected MCA behind such conditions are lacking, even if some of these conditions have recently been assigned to an International Classification of Diseases-10-Clinical Modification code (ICD-10-CM). In this article, we discuss diagnostic features and criteria and propose a ICD-10-CM-adjusted classification for disorders associated with MCA, herein referred to as MCA disorders (MCADs), with special emphasis on the delineation between confirmed MCAS, MCAD not fulfilling MCAS criteria, and suspected MCAD that is not present. In addition, we discuss the discrimination between overt MCAD and predisposing conditions, such as atopic states, mastocytosis, and hereditary alpha tryptasemia.

Standards of Pathology in the Diagnosis of Systemic Mastocytosis: Recommendations of the EU-US Cooperative Group

Pathology plays a central role in the diagnosis of systemic mastocytosis (SM), its delineation from other neoplasms and reactive conditions, and in monitoring of SM under therapy. The morphologic hallmark of SM is the accumulation of spindle-shaped, hypogranulated mast cells (MCs) in bone marrow (BM) and other extracutaneous tissues. Four of the 5 World Health Organization-defined diagnostic criteria (ie, compact MC aggregates [=major criterion]; atypical MC morphology; activating KIT point mutations; aberrant expression of CD25 and/or CD2 and/or CD30 in MCs [=minor criteria]) can be addressed by the pathologist. The final classification of SM variants as either BM mastocytosis, indolent SM, smoldering SM, aggressive SM (ASM), SM with an associated hematologic neoplasm (SM-AHN), or MC leukemia (MCL) has important prognostic significance and requires the integration of certain morphological, clinical, radiological, and biochemical data, referred to as B- and C-findings. Substantial diagnostic challenges may be posed to the pathologist and clinician especially in the so-called advanced SM variants, that is, ASM, MCL, and SM-AHN. In this article, updated recommendations of the EU-US Cooperative Group regarding standards of pathology in the diagnosis of SM, presented during the year 2020 Working Conference held in September in Vienna, are reported.

CDK4/CDK6 Inhibitors Synergize with Midostaurin, Avapritinib, and Nintedanib in Inducing Growth Inhibition in KIT D816V+ Neoplastic Mast Cells

Simple Summary

Advanced systemic mastocytosis (AdvSM) is a rare malignant disease with a poor prognosis due to the drug resistance of neoplastic mast cells. We found that drugs targeting the cell cycle regulators CDK4 and CDK6 profoundly suppress the growth and survival of neoplastic mast cells. Furthermore, these drugs can overcome resistance against KIT D816V-targeting drugs, including midostaurin, in neoplastic mast cells. Finally, the CDK4/CDK6 inhibitors applied induced apoptosis in CD34+/CD38− stem cells in AdvSM. Based on these results, we believe that CDK4/CDK6 inhibition may be a new and interesting therapeutic approach with curative potential for AdvSM. Whether combinations of KIT D816-targeting drugs and CDK4/CDK6 inhibitors can induce long-term remission in patients with AdvSM remains to be determined in clinical trials.

Abstract

In most patients with advanced systemic mastocytosis (AdvSM), neoplastic mast cells (MC) express KIT D816V. However, despite their disease-modifying potential, KIT D816V-targeting drugs, including midostaurin and avapritinib, may not produce long-term remissions in all patients. Cyclin-dependent kinase (CDK) 4 and CDK6 are promising targets in oncology. We found that shRNA-mediated knockdown of CDK4 and CDK6 results in growth arrest in the KIT D816V⁺ MC line HMC-1.2. The CDK4/CDK6 inhibitors palbociclib, ribociclib, and abemaciclib suppressed the proliferation in primary neoplastic MC as well as in all HMC-1 and ROSA cell subclones that were examined. Abemaciclib was also found to block growth in the drug-resistant MC line MCPV-1, whereas no effects were seen with palbociclib and ribociclib. Anti-proliferative drug effects on MC were accompanied by cell cycle arrest. Furthermore, CDK4/CDK6 inhibitors were found to synergize with the KIT-targeting drugs midostaurin, avapritinib, and nintedanib in inducing growth inhibition and apoptosis in neoplastic MCs. Finally, we found that CDK4/CDK6 inhibitors induce apoptosis in CD34+/CD38− stem cells in AdvSM. Together, CDK4/CDK6 inhibition is a potent approach to suppress the growth of neoplastic cells in AdvSM. Whether CDK4/CDK6 inhibitors can improve clinical outcomes in patients with AdvSM remains to be determined in clinical trials.

Abstract 6257: Mutations in the ASXL1 and ZRSR2 genes are associated with the response to the combination of alvocidib and 5-azacytidine in higher-risk myelodysplastic syndromes

The hypomethylating agent 5-azacytidine (5-Aza) is a standard-of-care for patients with higher-risk myelodysplastic syndromes (MDS). Although an initial response is induced in approximately 50% of 5-Aza treated patients, subsequent relapse is almost certain. Recently, inhibitors of anti-apoptotic BCL-2 protein family members have shown therapeutic potential in acute myeloid leukemia (AML) and higher-risk MDS. Alvocidib (Alv), a CDK9 inhibitor and indirect transcriptional repressor of the anti-apoptotic factor MCL-1, has shown anti-leukemic effects in a phase 1 study of patients with AML (Lee DJ et al, Expert Opin Investig Drugs 2019; Zeidner JF et al, Leuk Res 2015). A phase 1b/2 study with Alv and 5-Aza or decitabine in higher-risk patients with MDS was recently completed (NCT03593915); however, biomarkers for response to the Alv and 5-Aza combination are not well characterized. To identify potential biomarkers of response, we performed a comprehensive in vitro assessment of Alv and 5-Aza combination using a clinically well-characterized cohort of n=45 higher-risk patients with MDS and n=11 healthy controls (HC). CD34+ cells were purified from bone marrow (BM) aspirates using positive selection with MACS beads. CD34+ cells of HC were obtained from femur head replacement surgery bone specimens. After 4 days of expansion in SFEM II medium containing StemSpan Myeloid Expansion Supplement, cells were treated with 5-Aza for 48h, Alv for 24h or their combination (5-Aza for 48h followed by Alv for 24h). Cell viability was determined using CellTiter-Glo (CTG) and Annexin-V apoptosis assays. MCL-1 dependency of MDS samples was assessed using MS1 peptide-based assay. Recurrent myeloid neoplasia mutations in 67 genes were assessed in BM mononuclear cells using NGS panel deep sequencing. The combination of 5-Aza+Alv had an additive cytotoxic effect on CD34+ MDS cells in CTG assay (median cell viability = 74%, 73.8% and 55% for 5-Aza, Alv and combination respectively, p&lt;0.0001). In Annexin-V apoptosis assay, MDS samples were more sensitive to the combination treatment compared to HC (median % of apoptotic and dead cells = 36.6% for MDS vs 25.6% for HC, p=0.0288). MCL-1 dependency inversely and not significantly correlated with CD34+ cell viability in CTG assays (Spearman r=-0.37, p=0.1119). In contrast, we found significant associations between ASXL1 and ZRSR2 mutations and higher sensitivity of MDS samples to 5-Aza+Alv combination (p=0.008 and p=0.0005 in univariable analysis respectively). ZRSR2 mutations also retained an independent impact on cell viability in multivariable analysis (p=0.035). Overall, we provide pre-clinical support for the use of 5-Aza+Alv combination for higher-risk MDS and identified ASXL1 and ZRSR2 mutations as potential genetic biomarkers of augmented response.

Citation Format: Vladimir Ryabov, Nanni Schmitt, Qingyu Xu, Alexander Streuer, Johann-Christoph Jann, Alina Wein, Eva Altrock, Verena Nowak, Nadine Weimer, Julia Obländer, Iris Palme, Ahmed Jawhar, Ali Darwich, Patrick Wuchter, Christel Weiss, Georgia Metzgeroth, Jason M. Foulks, Laurenz Steiner, Mohamad Jawhar, Wolf-Karsten Hofmann, Daniel Nowak. Mutations in the ASXL1 and ZRSR2 genes are associated with the response to the combination of alvocidib and 5-azacytidine in higher-risk myelodysplastic syndromes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6257.

Standards of Genetic Testing in the Diagnosis and Prognostication of Systemic Mastocytosis in 2022: Recommendations of the EU-US Cooperative Group

Mastocytosis comprises rare heterogeneous diseases characterized by an increased accumulation of abnormal mast cells in various organs/tissues. The pathogenesis of mastocytosis is strongly linked to the presence of KIT-activating mutations. In systemic mastocytosis (SM), the most frequent mutation encountered is KIT p.D816V, whose presence constitutes one of the minor diagnostic criteria. Different techniques are used to search and quantify the KIT p.D816V mutant; however, allele-specific quantitative PCR and droplet digital PCR are today the most sensitive. The analysis of the KIT p.D816V allele burden has undeniable interest for diagnostic, prognostic, and therapeutic monitoring. The analysis of non-mast cell hematological compartments in SM is similarly important because KIT p.D816V multilineage involvement is associated with a worse prognosis. In addition, in advanced forms of SM, mutations in genes other than KIT are frequently identified and affect negatively disease outcome and response to therapy. Thus, combined quantitative and sensitive analysis of KIT mutations and next-generation sequencing of other recurrently involved myeloid genes make it possible to better characterize the extent of the affected cellular compartments and additional molecular aberrations, providing a more detailed overview of the complex mutational landscape of SM, in relation with the clinical heterogeneity of the disease. In this article, we report the latest recommendations of the EU-US Cooperative Group presented in September 2020 in Vienna during an international working conference, on the techniques we consider standard to detect and quantify the KIT p.D816V mutant in SM and additional myeloid mutations found in SM subtypes.

Superior Efficacy of Midostaurin Over Cladribine in Advanced Systemic Mastocytosis: A Registry-Based Analysis

PURPOSE

On the basis of data from the German Registry on Disorders of Eosinophils and Mast Cells, we compared the efficacy of midostaurin and cladribine in patients with advanced systemic mastocytosis (AdvSM).

PATIENTS AND METHODS

Patients with AdvSM (n = 139) were treated with midostaurin only (n = 63, 45%), cladribine only (n = 23, 17%), or sequentially (midostaurin-cladribine, n = 30, 57%; cladribine-midostaurin, n = 23, 43%). Prognosis was assessed through the Mutation-Adjusted Risk Score (MARS). Besides the comparison of efficacy between midostaurin and cladribine on response (eg, organ dysfunction, bone marrow mast cell [MC] infiltration, and tryptase), overall survival (OS), and leukemia-free survival, we focused on the impact of treatment on involved non-MC lineages, for example, monocytes or eosinophils, and the KIT D816V expressed allele burden.

RESULTS

Midostaurin only was superior to cladribine only with effects from responses on MC and non-MC lineages conferring on a significantly improved OS (median 4.2 v 1.9 years, P = .033) and leukemia-free survival (2.7 v 1.3 years, P = .044) on the basis of a propensity score-weighted analysis of parameters included in MARS. Midostaurin compensated the inferior efficacy of cladribine in first- and second-line treatment. On midostaurin in any line, response of eosinophilia did not improve its baseline adverse prognostic impact, whereas response of monocytosis proved to be a positive on-treatment parameter. Multivariable analysis allowed to establish three risk categories (low/intermediate/high) through the combination of MARS and the reduction of the KIT D816V expressed allele burden of ≥ 25% at month 6 (median OS not reached v 3.0 years v 1.0 year; P < .001).

CONCLUSION

In this registry-based analysis, midostaurin revealed superior efficacy over cladribine in patients with AdvSM. In midostaurin-treated patients, the combination of baseline MARS and molecular response provided a compelling three-tier risk categorization (MARSv2.0) for OS.

The insertion site is the main risk factor for central venous catheter-related complications in patients with hematologic malignancies

Central venous catheters (CVC) placed either via the internal jugular vein (IJV) or the subclavian vein (SCV) are routinely used in patients with hematologic malignancies. In this retrospective study, we systematically compared CVC-associated complications for both insertion sites, IJV and SCV. Between January 2011 and June 2013, all consecutive patients (n = 87) were included with at least one CVC (n = 153; n = 94 IJV; n = 59 SCV) at our institution due to induction/consolidation for AML/ALL or autologous hematopoietic cell transplantation (HCT). Primary study endpoints were central line-associated (CLABSI), catheter-related (CRBSI) blood stream infections and local inflammation (LI) at the insertion site. CRBSI occurred earlier and more frequently in the IJV- versus the SCV-group with an incidence rate of CRBSI at day 15 of 10% versus 0% (p = .04) and a rate of CRBSI per 1000 CVC days of 5.7 versus 1.2. In addition, CLABSI was detected more often in IJV- compared to SCV-CVC (26% vs. 8%, p = .009). Conversely, LI occurred more frequently and earlier in SCV- versus IJV-CVC (88% vs. 56%, p < .0001) with a median time to LI of 9 versus 14 days (p < .0001). The strongest risk factor for the endpoints CRBSI, CLABSI, and LI was the insertion site. However, SCV insertion was a risk factor for LI (p = .001, HR: 2.0), insertion in the IJV a risk factor for CLABSI (p = .044, HR: 2.7) and CRBSI (p = .036, HR: 5.4). These results demonstrate a differential effect of the insertion site of CVC in neutropenic patients with a significantly reduced frequency of CVC-related blood stream infections in SCV-CVC.

Refined diagnostic criteria for bone marrow mastocytosis: a proposal of the European competence network on mastocytosis

In the current classification of the World Health Organization (WHO), bone marrow mastocytosis (BMM) is a provisional variant of indolent systemic mastocytosis (ISM) defined by bone marrow involvement and absence of skin lesions. However, no additional diagnostic criteria for BMM have been proposed. Within the registry dataset of the European Competence Network on Mastocytosis, we compared characteristics and outcomes of 390 patients with BMM and 1175 patients with typical ISM. BMM patients were significantly older, predominantly male, had lower tryptase and lower burden of neoplastic mast cells, and displayed a higher frequency of allergic reactions, mainly triggered by Hymenoptera, than patients with typical ISM. The estimated 10-year progression-free survival of BMM and typical ISM was 95.9% and 92.6%, respectively. In BMM patients defined by WHO-based criteria, the presence of one B-Finding and tryptase level ≥125 ng/mL were identified as risk factors for progression in multivariate analyses. BMM patients without any of these risk factors were found to have better progression-free survival (p < 0.05) and better overall survival (p < 0.05) than other ISM patients. These data support the proposal to define BMM as a separate SM variant characterized by SM criteria, absence of skin lesions, absence of B-Findings, and tryptase levels <125 ng/mL.

Proposed Diagnostic Criteria and Classification of Canine Mast Cell Neoplasms: A Consensus Proposal

Mast cell neoplasms are one of the most frequently diagnosed malignancies in dogs. The clinical picture, course, and prognosis vary substantially among patients, depending on the anatomic site, grade and stage of the disease. The most frequently involved organ is the skin, followed by hematopoietic organs (lymph nodes, spleen, liver, and bone marrow) and mucosal sites of the oral cavity and the gastrointestinal tract. In cutaneous mast cell tumors, several grading and staging systems have been introduced. However, no comprehensive classification and no widely accepted diagnostic criteria have been proposed to date. To address these open issues and points we organized a Working Conference on canine mast cell neoplasms in Vienna in 2019. The outcomes of this meeting are summarized in this article. The proposed classification includes cutaneous mast cell tumors and their sub-variants defined by grading- and staging results, mucosal mast cell tumors, extracutaneous/extramucosal mast cell tumors without skin involvement, and mast cell leukemia (MCL). For each of these entities, diagnostic criteria are proposed. Moreover, we have refined grading and staging criteria for mast cell neoplasms in dogs based on consensus discussion. The criteria and classification proposed in this article should greatly facilitate diagnostic evaluation and prognostication in dogs with mast cell neoplasms and should thereby support management of these patients in daily practice and the conduct of clinical trials.

Updated Diagnostic Criteria and Classification of Mast Cell Disorders: A Consensus Proposal

Mastocytosis is a hematologic neoplasm characterized by expansion and focal accumulation of neoplastic mast cells (MC) in diverse organs, including the skin, bone marrow (BM), spleen, liver, and gastrointestinal tract. The World Health Organization classification divides the disease into prognostically distinct variants of cutaneous mastocytosis (CM) and systemic mastocytosis (SM). Although this classification remains valid, recent developments in the field and the advent of new diagnostic and prognostic parameters created a need to update and refine definitions and diagnostic criteria in MC neoplasms. In addition, MC activation syndromes (MCAS) and genetic features predisposing to SM and MCAS have been identified. To discuss these developments and refinements in the classification, we organized a Working Conference comprised of experts from Europe and the United States in August 2020. This article reports on outcomes from this conference. Of particular note, we propose adjustments in the classification of CM and SM, refinements in diagnostic criteria of SM variants, including smoldering SM and BM mastocytosis (BMM), and updated criteria for MCAS and other conditions involving MC. CD30 expression in MC now qualifies as a minor SM criterion, and BMM is now defined by SM criteria, absence of skin lesions and absence of B- and C-findings. A basal serum tryptase level exceeding 20 ng/mL remains a minor SM criterion, with recognition that hereditary alpha-tryptasemia and various myeloid neoplasms may also cause elevations in tryptase. Our updated proposal will support diagnostic evaluations and prognostication in daily practice and the conduct of clinical trials in MC disorders.

Preclinical evaluation of eltrombopag in a PDX model of myelodysplastic syndromes

Preclinical research of myelodysplastic syndromes (MDSs) is hampered by a lack of feasible disease models. Previously, we have established a robust patient-derived xenograft (PDX) model for MDS. Here we demonstrate for the first time that this model is applicable as a preclinical platform to address pending clinical questions by interrogating the efficacy and safety of the thrombopoietin receptor agonist eltrombopag. Our preclinical study included n = 49 xenografts generated from n = 9 MDS patient samples. Substance efficacy was evidenced by FACS-based human platelet quantification and clonal bone marrow evolution was reconstructed by serial whole-exome sequencing of the PDX samples. In contrast to clinical trials in humans, this experimental setup allowed vehicle- and replicate-controlled analyses on a patient–individual level deciphering substance-specific effects from natural disease progression. We found that eltrombopag effectively stimulated thrombopoiesis in MDS PDX without adversely affecting the patients’ clonal composition. In conclusion, our MDS PDX model is a useful tool for testing new therapeutic concepts in MDS preceding clinical trials.

Selecting the Right Criteria and Proper Classification to Diagnose Mast Cell Activation Syndromes: A Critical Review

In recent years, knowledge about mechanisms underlying mast cell activation (MCA) and accumulation in various pathologic conditions increased substantially. In addition, criteria and a classification of MCA syndromes (MCASs) have been set forth. MCAS is defined by typical clinical symptoms, a substantial increase in serum tryptase level during an attack over the patient's baseline tryptase, and a response of the symptoms to drugs targeting mast cells, mediator production, and/or mediator effects. Alternative diagnostic criteria of MCAS have also been suggested, but these alternative criteria often lack specificity and validation. In this report, we critically review the contemporary literature relating to MCAS and compare the specificity, sensitivity, and strength of MCAS-related parameters within proposals to diagnose and classify MCAS and its variants. Furthermore, we highlight the need to apply specific consensus criteria in the evaluation and classification of MCAS in individual patients. This is an urgent and important medical necessity because as an increasing number of patients are being given a misdiagnosis of MCAS based on nonspecific criteria, which contributes to confusion and frustration by patients and caregivers and sometimes may delay recognition and treatment of correct medical conditions that often turn out to be unrelated to MCA.

Clinical and histopathological features of myeloid neoplasms with concurrent Janus kinase 2 (JAK2) V617F and KIT proto-oncogene, receptor tyrosine kinase (KIT) D816V mutations

We report on 45 patients with myeloid neoplasms and concurrent Janus kinase 2 (JAK2) V617F and KIT proto-oncogene, receptor tyrosine kinase (KIT) D816V (JAK2^{pos .} /KIT^{pos .} ) mutations, which are individually identified in >60% of patients with classical myeloproliferative neoplasms (MPN) and >90% of patients with systemic mastocytosis (SM) respectively. In SM, the concurrent presence of a clonal non-mast cell neoplasm [SM with associated haematological neoplasm (SM-AHN)] usually constitutes a distinct subtype associated with poor survival. All 45 patients presented with a heterogeneous combination of clinical/morphological features typical of the individual disorders (e.g. leuco-/erythro-/thrombocytosis and elevated lactate dehydrogenase for MPN; elevated serum tryptase and alkaline phosphatase for SM). Overlapping features identified in 70% of patients included splenomegaly, cytopenia(s), bone marrow fibrosis and additional somatic mutations. Molecular dissection revealed discordant development of variant allele frequency for both mutations and absence of concurrently positive single-cell derived colonies, indicating disease evolution in two independent clones rather than monoclonal disease in >60% of patients examined. Overall survival of JAK2^{pos .} /KIT^{pos .} patients without additional somatic high-risk mutations [HRM, e.g. in serine and arginine-rich splicing factor 2 (SRSF2), additional sex combs like-1 (ASXL1) or Runt-related transcription factor 1 (RUNX1)] at 5 years was 77%, indicating that the mutual impact of JAK2 V617F and KIT D816V on prognosis is fundamentally different from the adverse impact of additional HRM in the individual disorders.

Proceedings from the Inaugural American Initiative in Mast Cell Diseases (AIM) Investigator Conference

The American Initiative in Mast Cell Diseases (AIM) held its inaugural investigator conference at Stanford University School of Medicine in May 2019. The overarching goal of this meeting was to establish a Pan-American organization of physicians and scientists with multidisciplinary expertise in mast cell disease. To serve this unmet need, AIM envisions a network where basic, translational, and clinical researchers could establish collaborations with both academia and biopharma to support the development of new diagnostic methods, enhanced understanding of the biology of mast cells in human health and disease, and the testing of novel therapies. In these AIM proceedings, we highlight selected topics relevant to mast cell biology and provide updates regarding the recently described hereditary alpha-tryptasemia. In addition, we discuss the evaluation and treatment of mast cell activation (syndromes), allergy and anaphylaxis in mast cell disorders, and the clinical and biologic heterogeneity of the more indolent forms of mastocytosis. Because mast cell disorders are relatively rare, AIM hopes to achieve a coordination of scientific efforts not only in the Americas but also in Europe by collaborating with the well-established European Competence Network on Mastocytosis.

Clinical Impact of Inherited and Acquired Genetic Variants in Mastocytosis

Mastocytosis is a rare and complex disease characterized by expansion of clonal mast cells (MC) in skin and/or various internal organ systems. Involvement of internal organs leads to the diagnosis of systemic mastocytosis (SM). The WHO classification divides SM into indolent SM, smoldering SM and advanced SM variants, including SM with an associated hematologic neoplasm, aggressive SM, and MC leukemia. Historically, genetic analysis of individuals with pure cutaneous mastocytosis (CM) and SM have focused primarily on cohort studies of inherited single nucleotide variants and acquired pathogenic variants. The most prevalent pathogenic variant (mutation) in patients with SM is KIT p.D816V, which is detectable in most adult patients. Other somatic mutations have also been identified-especially in advanced SM-in TET2, SRSF2, ASXL1, RUNX1, CBL and JAK2, and shown to impact clinical and cellular phenotypes. Although only small patient cohorts have been analyzed, disease associations have also been identified in several germline variants within genes encoding certain cytokines or their receptors (IL13, IL6, IL6R, IL31, IL4R) and toll-like receptors. More recently, an increased prevalence of hereditary alpha-tryptasemia (HαT) caused by increased TPSAB1 copy number encoding alpha-tryptase has been described in patients with SM. Whereas HαT is found in 3-6% of general Western populations, it is identified in up to 17% of patients with SM. In the current manuscript we review the prevalence, functional role and clinical impact of various germline and somatic genetic variants in patients with mastocytosis.

Cytogenetic and molecular aberrations and worse outcome for male patients in systemic mastocytosis

In systemic mastocytosis (SM), the clinical features and survival vary greatly. Patient-related factors determining the outcome in SM are largely unknown. Methods: We examined the impact of sex on the clinical features, progression-free survival (PFS), and overall survival (OS) in 3403 patients with mastocytosis collected in the registry of the European Competence Network on Mastocytosis (ECNM). The impact of cytogenetic and molecular genetic aberrations on sex differences was analyzed in a subset of patients. Results: Of all patients enrolled, 55.3% were females. However, a male predominance was found in a subset of advanced SM (AdvSM) patients, namely SM with an associated hematologic neoplasm (SM-AHN, 70%; p < 0.001). Correspondingly, organomegaly (male: 23% vs. female: 13%, p = 0.007) was more, whereas skin involvement (male: 71% vs. female: 86%, p = 0.001) was less frequent in males. In all patients together, OS (p < 0.0001) was significantly inferior in males, and also within the WHO sub-categories indolent SM, aggressive SM (ASM) and SM-AHN. PFS was significantly (p = 0.0002) worse in males when all patients were grouped together; due to low numbers of events, this significance persisted only in the subcategory smoldering SM. Finally, prognostically relevant cytogenetic abnormalities (10% vs. 5%, p = 0.006) or molecular aberrations (SRSF2/ASXL1/RUNX1 profile; 63% vs. 40%, p = 0.003) were more frequently present in males. Conclusions: Male sex has a major impact on clinical features, disease progression, and survival in mastocytosis. Male patients have an inferior survival, which seems related to the fact that they more frequently develop a multi-mutated AdvSM associated with a high-risk molecular background.

Scoring the Risk of Having Systemic Mastocytosis in Adult Patients with Mastocytosis in the Skin

BACKGROUND

Mastocytosis in adults often presents with skin lesions. A bone marrow biopsy is necessary to confirm or exclude the presence of systemic mastocytosis (SM) in these cases. When a bone marrow biopsy is not performed, the provisional diagnosis is mastocytosis in the skin (MIS). No generally accepted scoring system has been established to estimate the risk of SM in these patients.

OBJECTIVE

To develop a risk score to predict SM in adults with MIS.

METHODS

We examined 1145 patients with MIS from the European Competence Network on Mastocytosis Registry who underwent a bone marrow biopsy. A total of 944 patients had SM and 201 patients had cutaneous mastocytosis; 63.7% were female, and 36.3% were male. Median age was 44 ± 13.3 years. The median serum tryptase level amounted to 29.3 ± 81.9 ng/mL. We established a multivariate regression model using the whole population of patients as a training and validation set (bootstrapping). A risk score was developed and validated with receiver-operating curves.

RESULTS

In the multivariate model, the tryptase level (P < .001), constitutional/cardiovascular symptoms (P = .014), and bone symptoms/osteoporosis (P < .001) were independent predictors of SM (P < .001; sensitivity, 90.7%; specificity, 69.1%). A 6-point risk score was established (risk, 10.7%-98.0%) and validated.

CONCLUSIONS

Using a large data set of the European Competence Network on Mastocytosis Registry, we created a risk score to predict the presence of SM in patients with MIS. Although the score will need further validation in independent cohorts, our score seems to discriminate safely between patients with SM and with pure cutaneous mastocytosis.

Topical Treatment of Acyclovir-Resistant Herpes Simplex Virus Stomatitis after Allogeneic Hematopoietic Cell Transplantation

INTRODUCTION

We report on patients who developed severe acyclovir-resistant (ACVr) herpes simplex virus 1 (HSV-1) stomatitis after allogeneic hematopoietic cell transplantation (HCT).

PATIENTS

HCT patients suffering from HSV-1 stomatitis without response after 1 week of high-dose acyclovir (ACV) were tested for ACV resistance. Patients with proven ACV resistance were treated either topically with cidofovir solution and gel or with topical foscavir cream or with intravenous foscavir.

RESULTS

Among 214 consecutive HCT patients, 6 developed severe ACVr HSV-1 stomatitis (WHO grade III n = 1, WHO grade IV n = 5). All 6 patients suffered from relapse of acute myeloid leukemia (AML) after HCT. ACVr stomatitis was treated topically with first-line (n = 4) or second-line (n = 2) cidofovir. Topical foscavir cream was applied as first-line (n = 1) or second-line (n = 1) therapy. Intravenous foscavir was used in 3 patients (first-line therapy, n = 1; second-line therapy, n = 2). Complete remission was reached by topical cidofovir (n = 3), topical foscavir (n = 1), and intravenous foscavir (n = 1), respectively. Five of the 6 patients died due to progression of leukemia. Only 1 patient survived.

CONCLUSIONS

ACVr HSV-1 stomatitis is a severe complication in AML patients relapsing after HCT. It reflects the seriously impaired general condition of these patients. This analysis shows that topical treatment with cidofovir or foscavir might be a sufficient first-line therapy approach in ACVr HSV-1 stomatitis. It might serve as a less toxic alternative to intravenous foscavir.

Clinical features and survival of patients with indolent systemic mastocytosis defined by the updated WHO classification

BACKGROUND

In indolent systemic mastocytosis (ISM), several risk factors of disease progression have been identified. Previous studies, performed with limited patient numbers, have also shown that the clinical course in ISM is stable and comparable to that of cutaneous mastocytosis (CM). The aim of this project was to compare the prognosis of patients with ISM with that of patients with CM.

METHODS

We employed a dataset of 1993 patients from the registry of the European Competence Network on Mastocytosis (ECNM) to compare outcomes of ISM and CM.

RESULTS

We found that overall survival (OS) is worse in ISM compared to CM. Moreover, in patients with typical ISM, bone marrow mastocytosis (BMM), and smoldering SM (SSM), 4.1% of disease progressions have been observed (4.9% of progressions in typical ISM group, 1.7% in BMM, and 9.4% in SSM). Progressions to advanced SM were observed in 2.9% of these patients. In contrast, six patients with CM (1.7%) converted to ISM and no definitive progression to advanced SM was found. No significant differences in OS and event-free survival (EFS) were found when comparing ISM, BMM, and SSM. Higher risk of both progression and death was significantly associated with male gender, worse performance status, and organomegaly.

CONCLUSION

Our data confirm the clinical impact of the WHO classification that separates ISM from CM and from other SM variants.

Risk and management of patients with mastocytosis and MCAS in the SARS-CoV-2 (COVID-19) pandemic: Expert opinions

The coronavirus disease 2019 (COVID-19) (caused by severe acute respiratory syndrome coronavirus 2) pandemic has massively distorted our health care systems and caused catastrophic consequences in our affected communities. The number of victims continues to increase, and patients at risk can only be protected to a degree, because the virulent state may be asymptomatic. Risk factors concerning COVID-19-induced morbidity and mortality include advanced age, an impaired immune system, cardiovascular or pulmonary diseases, obesity, diabetes mellitus, and cancer treated with chemotherapy. Here, we discuss the risk and impact of COVID-19 in patients with mastocytosis and mast cell activation syndromes. Because no published data are yet available, expert opinions are, by necessity, based on case experience and reports from patients. Although the overall risk to acquire the severe acute respiratory syndrome coronavirus 2 may not be elevated in mast cell disease, certain conditions may increase the risk of infected patients to develop severe COVID-19. These factors include certain comorbidities, mast cell activation-related events affecting the cardiovascular or bronchopulmonary system, and chemotherapy or immunosuppressive drugs. Therefore, such treatments should be carefully evaluated on a case-by-case basis during a COVID-19 infection. In contrast, other therapies, such as anti-mediator-type drugs, venom immunotherapy, or vitamin D, should be continued. Overall, patients with mast cell disorders should follow the general and local guidelines in the COVID-19 pandemic and advice from their medical provider.

Response to tyrosine kinase inhibitors in myeloid neoplasms associated with PCM1-JAK2, BCR-JAK2 and ETV6-ABL1 fusion genes

We report on 18 patients with myeloid neoplasms and associated tyrosine kinase (TK) fusion genes on treatment with the TK inhibitors (TKI) ruxolitinib (PCM1-JAK2, n = 8; BCR-JAK2, n = 1) and imatinib, nilotinib or dasatinib (ETV6-ABL1, n = 9). On ruxolitinib (median 24 months, range 2-36 months), a complete hematologic response (CHR) and complete cytogenetic response (CCR) was achieved by five of nine and two of nine patients, respectively. However, ruxolitinib was stopped in eight of nine patients because of primary resistance (n = 3), progression (n = 3) or planned allogeneic stem cell transplantation (allo SCT, n = 2). At a median of 36 months (range 4-78 months) from diagnosis, five of nine patients are alive: four of six patients after allo SCT and one patient who remains on ruxolitinib. In ETV6-ABL1 positive patients, a durable CHR was achieved by four of nine patients (imatinib with one of five, nilotinib with two of three, dasatinib with one of one). Because of inadequate efficacy (lack of hematological and/or cytogenetic/molecular response), six of nine patients (imatinib, n = 5; nilotinib, n = 1) were switched to nilotinib or dasatinib. At a median of 23 months (range 3-60 months) from diagnosis, five of nine patients are in CCR or complete molecular response (nilotinib, n = 2; dasatinib, n = 2; allo SCT, n = 1) while two of nine patients have died. We conclude that (a) responses on ruxolitinib may only be transient in the majority of JAK2 fusion gene positive patients with allo SCT being an important early treatment option, and (b) nilotinib or dasatinib may be more effective than imatinib to induce durable complete remissions in ETV6-ABL1 positive patients.

EVALUATION OF XYLANASE PRODUCTION FROM FILAMENTOUS FUNGI WITH DIFFERENT LIFESTYLES

Xylanase plays an important role in the food, feed, and pulp/paper industry. Filamentous fungi have been considered as useful producers of this enzyme from an industrial point of view, due to the fact that they excrete xylanases into the medium. In this study, four fungal species belonging to different genera, i.e. Aspergillus, Cochliobolus, Pyrenophora, and Penicillium were isolated from different sources and compared for their ability to produce xylanase in submerged culture. The fungal species showed enzyme activity as determined by dinitrosalicylic acid (DNS) method. It was found that the two saprophytic Aspergillus strains, i.e A. terreus (Fss 129) and A. niger (SS7) had the highest xylanase activity of 474 and 294 U ml–1 at pH 7 and 8, respectively, in the presence of corn cob hulls after 120 h of incubation. The production of xylanase seemed to be strongly influenced by the interactive effect of initial pH on the fungi. Interestingly, xylanase was better produced by the saprophytic fungi of Aspergillus and Penicillium than by the plant pathogenic ones of Cochliobolus and Pyrenophora. This work provides additional information to support future research on fungi with different lifestyles for food industrial production of xylanase.

Importance of Adequate Diagnostic Workup for Correct Diagnosis of Advanced Systemic Mastocytosis

BACKGROUND

Little is known about the epidemiology of advanced systemic mastocytosis (advSM).

OBJECTIVES

To investigate epidemiologic features and diagnostic pitfalls of advSM in Germany.

METHODS

Therefore, 140 patients from a single German reference center of the European Competence Network on Mastocytosis between 2003 and 2018 were analyzed.

RESULTS

The patients' median age was 68 years (range, 26-86 years), and male versus female ratio was 2:1. An elevated serum tryptase, a KIT D816 mutation, and additional somatic mutations, for example, in SRSF2, ASXL1, or RUNX1, were identified in 95%, 91%, and 74% of patients, respectively. Median overall survival was 3.5 years (range, 0.03-14.3 years; male vs female 2.6 vs 4.2 years; P = .02). Two categories of misdiagnoses were identified in 51 of 140 (36%) patients: First, systemic mastocytosis (SM) was overlooked in 28 of 140 (20%) patients primarily diagnosed with various subtypes of myeloid neoplasms. Second, 23 of 140 (16%) patients were diagnosed with supposed progression from indolent SM to advSM; however, combination of an elevated KIT D816V variant allele frequency in peripheral blood (n = 22), monocytosis (n = 9), eosinophilia (n = 6), and/or mutations in SRSF2, ASXL1, or RUNX1 (n = 10) suggest that distinct signs of potential advSM were overlooked in virtually all patients. Based on locally diagnosed patients in an area of 2.5 million inhabitants, but obviously without considering more, yet unrecognized cases, the incidence and prevalence of advSM is at least 0.8 and 5.2, respectively, per 1 million inhabitants.

CONCLUSIONS

Adequate analyses of tryptase levels, bone marrow morphology, and genetics in patients with myeloid neoplasms or SM would help to prevent the significant underdiagnosis of advSM.

Influence of the Insertion Site on Central Venous Catheter-Related Complications in Patients Undergoing Allogeneic Hematopoietic Cell Transplantation

Central venous catheters (CVCs) are extensively used in patients undergoing allogeneic hematopoietic cell transplantation (HCT). In these patients CVC are placed routinely either via the internal jugular vein (IJV) or the subclavian vein (SCV). Purpose of this study was to systematically analyze complications of CVC at different insertion sites in HCT recipients. In this retrospective analysis, all consecutive patients (n = 56) who received a CVC (n = 101) due to allogeneic HCT at our institution between January 2011 and June 2013 were included. Three-lumen standard, nontunneled CVCs were placed via either the IJV (n = 60; 59%) or the SCV (n = 41; 41%). Study endpoints were time to local inflammation at the insertion site, time to fever, time to a combined endpoint of inflammation and fever, central line-associated bloodstream infection (CLABSI), duration of catheterization, catheter lumen obstruction, deep-vein thrombosis, pneumothorax, and catheter-related death. The median duration of catheterization per CVC was almost identical for the IJV and SCV sites (18 days versus 17 days; P not significant). There were no differences in the frequency of CLABSI, deep-vein thrombosis, pneumothorax, and catheter lumen obstruction between IJV and SCV CVC insertion sites. None of the patients died due to a CVC-related cause. Local inflammation occurred less frequently (48% versus 71%; P = .025) and later (median time to local inflammation, 25 days versus 12 days; P = .01) in IJV CVCs versus SCV CVCs. There was a trend toward a median longer time to the occurrence of fever for IJV CVCs compared with SCV CVCs (20 days versus 13 days; P = .07). In the multivariate analysis, diagnosis of acute leukemia (hazard ratio [HR], 1.696; P = .036), SCV CVC (HR, 1.617; P  = .039), and neutropenic CVC-days (HR, 2.477; P = .01) were identified as risk factors for the occurrence of local inflammation or fever. In contrast to earlier studies in patients without hematologic malignancies, these data demonstrate that CVCs placed in the SCV are not superior over IJV CVCs. Moreover, local inflammation occurred earlier and more frequently in patients with an SCV CVC.

An increased bone mineral density is an adverse prognostic factor in patients with systemic mastocytosis

PURPOSE

Systemic mastocytosis (SM) is characterized by the expansion of clonal mast cells that infiltrate various organ systems. The extent of organ infiltration and subsequent organ damage distinguishes between indolent SM (ISM) defined by a nearly normal life expectancy and advanced SM (AdvSM) defined by poor prognosis. In ISM, measurement of the bone mineral density (BMD) frequently reveals osteoporosis. In contrast, the clinical implication of an increased BMD and osteosclerosis remains unclear.

METHODS

BMD was evaluated in 61 patients with mastocytosis (ISM, n = 29, 48%; AdvSM, n = 32, 52%). We correlated the prevalence of osteoporosis, increased BMD and osteosclerosis with clinical parameters, disease variant and prognosis.

RESULTS

Osteoporosis was detected in 11/29 (38%) patients with ISM but only in 2/32 (6%) patients with AdvSM (p = 0.004). An increased BMD was detected in 1/29 (3%) patients with ISM and 24/32 (75%) patients with AdvSM (p < 0.001) while osteosclerosis was only detected in AdvSM patients (16/32, 50%). AdvSM patients with increased BMD had higher levels of bone marrow mast cell infiltration, higher serum tryptase and alkaline phosphatase levels compared to ISM as well as higher number of high-molecular risk mutations (p < 0.05). In addition, we found that the prognosis of AdvSM patients with increased BMD is inferior compared to those without increased BMD (median overall survival 3.6 years versus not reached, p = 0.031).

CONCLUSIONS

Osteoporosis is a common feature in ISM but not in AdvSM. An increased BMD is frequently present in AdvSM but not in ISM and is associated with more advanced disease and inferior outcome.

International prognostic scoring system for mastocytosis (IPSM): a retrospective cohort study

BACKGROUND

The WHO classification separates mastocytosis into distinct variants, but prognostication remains a clinical challenge. The aim of this study was to improve prognostication for patients with mastocytosis.

METHODS

We analysed data of the registry of the European Competence Network on Mastocytosis including 1639 patients (age 17-90 years) diagnosed with mastocytosis according to WHO criteria between Jan 12, 1978, and March 16, 2017. Univariate and multivariate analyses with Cox regression were applied to identify prognostic variables predicting survival outcomes and to establish a prognostic score. We validated this International Prognostic Scoring System in Mastocytosis (IPSM) with data of 462 patients (age 17-79 years) from the Spanish network Red Española de Mastocitosis diagnosed between Jan 22, 1998, and Nov 2, 2017.

FINDINGS

The prognostic value of the WHO classification was confirmed in our study (p<0·0001). For patients with non-advanced mastocytosis (n=1380), we identified age 60 years or older (HR 10·75, 95% CI 5·68-20·32) and a concentration of alkaline phosphatase 100 U/L or higher (2·91, 1·60-5·30) as additional independent prognostic variables for overall survival. The resulting scoring system divided patients with non-advanced mastocytosis into three groups: low (no risk factors), intermediate 1 (one risk factor), and intermediate 2 (two risk factors). Overall survival and progression-free survival differed significantly among these groups (p<0·0001). In patients with advanced mastocytosis (n=259), age 60 years or older (HR 2·14, 95% CI 1·42-3·22), a concentration of tryptase 125 ng/mL or higher (1·81, 1·20-2·75), a leukocyte count of 16 × 10⁹ per L or higher (1·88, 1·27-2·79), haemoglobin of 11 g/dL or lower (1·71, 1·13-2·57), a platelet count of 100 × 10⁹ per L or lower (1·63, 1·13-2·34), and skin involvement (0·46, 0·30-0·69) were prognostic variables. Based on these variables, a separate score for advanced mastocytosis with four risk categories was established, with significantly different outcomes for overall survival and progression-free survival (p<0·0001). The prognostic value of both scores was confirmed in 413 patients with non-advanced disease and 49 with advanced mastocytosis from the validation cohort.

INTERPRETATION

The IPSM scores for patients with non-advanced and advanced mastocytosis can be used to predict survival outcomes and guide treatment decisions. However, the predictive value of the IPSM needs to be confirmed in forthcoming trials.

FUNDING

Austrian Science Fund, Deutsche Forschungsgemeinschaft, Koeln Fortune Program, Charles and Ann Johnson Foundation, Instituto de Salud Carlos III, Fondos FEDER, Research-Foundation Flanders/Fonds Wetenschappelijk Onderzoek, Clinical Research-Fund of the University Hospitals Leuven, and Research-Foundation Flanders/Fonds Wetenschappelijk Onderzoek.

MARS: Mutation-Adjusted Risk Score for Advanced Systemic Mastocytosis

PURPOSE

To develop a risk score for patients with advanced systemic mastocytosis (AdvSM) that integrates clinical and mutation characteristics.

PATIENTS AND METHODS

The study included 383 patients with AdvSM from the German Registry on Disorders of Eosinophils and Mast Cells (training set; n = 231) and several centers for mastocytosis in the United States and Europe, all within the European Competence Network on Mastocytosis (validation set; n = 152). A Cox multivariable model was used to select variables that were predictive of overall survival (OS).

RESULTS

In multivariable analysis, the following risk factors were identified as being associated with OS: age greater than 60 years, anemia (hemoglobin < 10 g/dL), thrombocytopenia (platelets < 100 × 10⁹/L), presence of one high molecular risk gene mutation (ie, in SRSF2, ASXL1, and/or RUNX1), and presence of two or more high molecular risk gene mutations. By assigning hazard ratio–weighted points to these variables, the following three risk categories were defined: low risk (median OS, not reached), intermediate risk (median OS, 3.9 years; 95% CI, 2.1 to 5.7 years), and high risk (median OS, 1.9 years; 95% CI, 1.3 to 2.6 years; P < .001). The mutation-adjusted risk score (MARS) was independent of the WHO classification and was confirmed in the independent validation set. During a median follow-up time of 2.2 years (range, 0 to 23 years), 63 (16%) of 383 patients experienced a leukemic transformation to secondary mast cell leukemia (32%) or secondary acute myeloid leukemia (68%). The MARS was also predictive for leukemia-free survival (P < .001).

CONCLUSION

The MARS is a validated, five-parameter, WHO-independent prognostic score that defines three risk groups among patients with AdvSM and may improve up-front treatment stratification for these rare hematologic neoplasms.

KIT D816 mutated/CBF-negative acute myeloid leukemia: a poor-risk subtype associated with systemic mastocytosis

KIT D816 mutations (KIT D816mut) are strongly associated with systemic mastocytosis (SM) but are also detectable in acute myeloid leukemia (AML), where they represent an adverse prognostic factor in combination with core binding factor (CBF) fusion genes. Here, we evaluated the clinical and molecular features of KIT D816mut/CBF-negative (CBFneg) AML, a previously uncharacterized combination. All KIT D816mut/CBFneg cases (n = 40) had histologically proven SM with associated AML (SM-AML). Molecular analyses revealed at least one additional somatic mutation (median, n = 3) beside KIT D816 (e.g., SRSF2, 38%; ASXL1, 31%; RUNX1, 34%) in 32/32 (100%) patients. Secondary AML evolved in 29/40 (73%) patients from SM ± associated myeloid neoplasm. Longitudinal molecular and cytogenetic analyses revealed the acquisition of new mutations and/or karyotype evolution in 15/16 (94%) patients at the time of SM-AML. Median overall survival (OS) was 5.4 months. A screen of two independent AML databases (AMLdatabases) revealed remarkable similarities between KIT D816mut/CBFneg SM-AML and KIT D816mut/CBFneg AMLdatabases (n = 69) with regard to KIT D816mut variant allele frequency, mutation profile, aberrant karyotype, and OS suggesting underlying SM in a significant proportion of AMLdatabases patients. Bone marrow histology and reclassification as SM-AML has important clinical implications regarding prognosis and potential inclusion of KIT inhibitors in treatment concepts.

Identification of a leukemia-initiating stem cell in human mast cell leukemia

Mast cell leukemia (MCL) is a highly fatal malignancy characterized by devastating expansion of immature mast cells in various organs. Although considered a stem cell disease, little is known about MCL-propagating neoplastic stem cells. We here describe that leukemic stem cells (LSCs) in MCL reside within a CD34⁺/CD38⁻ fraction of the clone. Whereas highly purified CD34⁺/CD38⁻ cells engrafted NSG_hSCF mice with fully manifesting MCL, no MCL was produced by CD34⁺/CD38⁺ progenitors or the bulk of KIT⁺/CD34⁻ mast cells. CD34⁺/CD38⁻ MCL cells invariably expressed CD13 and CD133, and often also IL-1RAP, but did not express CD25, CD26 or CLL-1. CD34⁺/CD38⁻ MCL cells also displayed several surface targets, including CD33, which was homogenously expressed on MCL LSC in all cases, as well as the D816V mutant form of KIT. Whereas CD34⁺/CD38⁻ cells were resistant against single drugs, exposure to combinations of CD33-targeting and KIT-targeting drugs resulted in LSC-depletion and markedly reduced engraftment in NSG_hSCF mice. Together, MCL LSCs are CD34⁺/CD38⁻ cells that express distinct profiles of markers and target antigens. Characterization of MCL LSCs should facilitate their purification and should support the development of LSC-eradicating curative treatment approaches in this fatal type of leukemia.

Inhibitory effects of midostaurin and avapritinib on myeloid progenitors derived from patients with KIT D816V positive advanced systemic mastocytosis

Advanced systemic mastocytosis (advSM) is characterized by the presence of an acquired KIT D816V mutation in >90% of patients. In the majority of patients, KIT D816V is not only detected in mast cells but also in other hematopoietic lineages. We sought to investigate the effects of the KIT-inhibitors midostaurin and avapritinib on single-cell-derived myeloid progenitor cells using granulocyte-macrophage colony-forming-units of patients with KIT D816V positive advSM. Colonies obtained prior to treatment were incubated in vitro with midostaurin (n = 10) or avapritinib (n = 11) and showed a marked reduction (≥50%) of KIT D816V positive colonies in 3/10 (30%) and 7/11 (64%) patient samples, respectively. Three of those 7 (43%) avapritinib responders were resistant to midostaurin in both, in vitro and in vivo. Colonies from four patients with high-risk molecular profile and aggressive clinical course were resistant to both drugs. The in vitro activity of midostaurin strongly correlated with clinical and molecular responses, e.g., relative reduction of KIT D816V allele burden and the proportion of KIT D816V positive colonies obtained after six months midostaurin-treatment in vivo. We conclude that the colony inhibition assay provides useful information for prediction of responses on midostaurin and that avapritinib has a superior in vitro activity compared to midostaurin.

The Data Registry of the European Competence Network on Mastocytosis (ECNM): Set Up, Projects, and Perspectives

Mastocytosis is a unique hematologic neoplasm with complex biology and pathology and a variable clinical course. The disease can essentially be divided into cutaneous mastocytosis (CM) and systemic mastocytosis (SM). In adults, SM is diagnosed in most cases and manifests as either indolent or advanced disease. Patients with advanced SM have an unfavorable prognosis with reduced survival. However, so far, little is known about the prevalence of various categories of SM and about prognostic factors. In an attempt to learn more about the behavior and evolution of various forms of CM and SM, the European Competence Network on Mastocytosis (ECNM) initiated a mastocytosis registry in 2012. In this article, the set up and start phase of this registry are described. Until 2018, more than 3000 patients from 12 countries and 25 centers have been enrolled. In a majority of all patients, robust follow-up data and relevant clinical end points are available. Using this data set, a series of registry projects have been launched, with the aim to validate previously identified diagnostic and prognostic variables and to identify new disease-related and patient-related parameters in various forms of mastocytosis. Moreover, the core data set of the registry will be useful to establish multiparametric scoring systems through which prognostication and individualized management of patients with mastocytosis should improve in the foreseeable future.

Recurrent activating STAT5B N642H mutation in myeloid neoplasms with eosinophilia

Determining the underlying cause of persistent eosinophilia is important for effective clinical management but remains a diagnostic challenge in many cases. We identified STAT5B N642H, an established oncogenic mutation, in 27/1715 (1.6%) cases referred for investigation of eosinophilia. Of the 27 mutated cases, a working diagnosis of hypereosinophilic syndrome (HES; n = 7) or a myeloid neoplasm with eosinophilia (n = 20) had been made prior to the detection of STAT5B N642H. Myeloid panel analysis identified a median of 2 additional mutated genes (range 0–4) with 4 cases having STAT5B N642H as a sole abnormality. STAT5B N642H was absent in cultured T cells of 4/4 positive cases. Individuals with SF3B1 mutations (9/27; 33%) or STAT5B N642H as a sole abnormality had a markedly better overall survival compared to cases with other additional mutations (median 65 months vs. 14 months; hazard ratio = 8.1; P < 0.001). The overall survival of STAT5B-mutated HES cases was only 30 months, suggesting that these cases should be reclassified as chronic eosinophilic leukemia, not otherwise specified (CEL-NOS). The finding of STAT5B N642H as a recurrent mutation in myeloid neoplasia with eosinophilia provides a new diagnostic and prognostic marker as well as a potential target for therapy.

Course of colonization by multidrug-resistant organisms after allogeneic hematopoietic cell transplantation

Multidrug-resistant organisms (MDRO) have been developing as an emerging problem in allogeneic hematopoietic cell transplantation (HCT). Since no data are available on the course of MDRO colonization after HCT, we investigated in this retrospective, single-center study, persistence and clearance of MDRO after HCT. From June 2010 to December 2015, 121 consecutive HCT patients were included. Patients received a MDRO screening before conditioning as well as surveillance cultures after HCT. In MDRO-colonized patients, surveillance specimens were taken until MDRO were no longer detectable. Thirty-three patients (27%) were found to be colonized by at least one MDRO at any time point until day 100 post HCT. Day 100 (2-year) non-relapse mortality (NRM) and overall survival (OS) of MDRO-colonized (MDRO⁺) versus non-colonized (MDRO^-) patients were essentially the same. NRM is 15% (21%) versus 15% (24%). Two-year OS is 60 versus 55% for MDRO⁺ versus MDRO^- patients. Out of the 33 MDRO⁺ patients, 21 cleared the MDRO. Median time to non-detectability of MDRO was 6 months. In 12 patients, the MDRO persisted. There was a significant (p < 0.0001) survival difference between patients who cleared the MDRO versus those with MDRO persistence (2-year OS 80 vs 40%). Except for the length of antibiotic therapy as a potential risk factor for MDRO persistence after HCT, no other conventional factors could be identified. (a) colonization by MDRO per se had no negative impact on the outcome, (b) MDRO can be cleared by the majority of patients after allogeneic HCT, and (c) to increase the probability to clear MDRO, the use of antibiotics in MDRO⁺ patients should be reviewed critically.

Incidence and prognostic impact of cytogenetic aberrations in patients with systemic mastocytosis

The clinical behavior of systemic mastocytosis (SM) is strongly associated with activating mutations in KIT (D816V in >80% of cases), with the severity of the phenotype influenced by additional somatic mutations, for example, in SRSF2, ASXL1, or RUNX1. Complex molecular profiles are frequently associated with the presence of an associated hematologic neoplasm (AHN) and an unfavorable clinical outcome. However, little is known about the incidence and prognostic impact of cytogenetic aberrations. We analyzed cytogenetic and molecular characteristics of 109 patients (KIT D816V+, n = 102, 94%) with indolent (ISM, n = 26) and advanced SM (n = 83) with (n = 73, 88%) or without AHN. An aberrant karyotype was identified in SM-AHN (16/73, 22%) patients only. In patients with an aberrant karyotype, additional somatic mutations were identified in 12/16 (75%) patients. Seven of 10 (70%) patients with a poor-risk karyotype, for example, monosomy 7 or complex karyotype, and 1/6 (17%) patients with a good-risk karyotype progressed to secondary acute myeloid leukemia (n = 7) or mast cell leukemia (n = 1) within a median of 40 months (range 2-190, P = .04). In advanced SM, the median overall survival (OS) of poor-risk karyotype patients was significantly shorter than in good-risk/normal karyotype patients (4 vs 39 months; hazard ratio 11.7, 95% CI 5.0-27.3; P < .0001). Additionally, the shortened OS in patients with poor-risk karyotype was independent from the mutation status. In summary, a poor-risk karyotype is an independent prognostic variable in advanced SM. Cytogenetic and molecular analyses should be routinely performed in all patients with advanced SM ± AHN because these investigations greatly support prognostication and treatment decisions.

The KIT and PDGFRA switch-control inhibitor DCC-2618 blocks growth and survival of multiple neoplastic cell types in advanced mastocytosis

Systemic mastocytosis is a complex disease defined by abnormal growth and accumulation of neoplastic mast cells in various organs. Most patients exhibit a D816V-mutated variant of KIT, which confers resistance against imatinib. Clinical problems in systemic mastocytosis arise from mediator-related symptoms and/or organ destruction caused by malignant expansion of neoplastic mast cells and/or other myeloid cells in various organ systems. DCC-2618 is a spectrum-selective pan KIT and PDGFRA inhibitor which blocks KIT D816V and multiple other kinase targets relevant to systemic mastocytosis. We found that DCC-2618 inhibits the proliferation and survival of various human mast cell lines (HMC-1, ROSA, MCPV-1) as well as primary neoplastic mast cells obtained from patients with advanced systemic mastocytosis (IC₅₀ <1 μM). Moreover, DCC-2618 decreased growth and survival of primary neoplastic eosinophils obtained from patients with systemic mastocytosis or eosinophilic leukemia, leukemic monocytes obtained from patients with chronic myelomonocytic leukemia with or without concomitant systemic mastocytosis, and blast cells obtained from patients with acute myeloid leukemia. Furthermore, DCC-2618 was found to suppress the proliferation of endothelial cells, suggesting additional drug effects on systemic mastocytosis-related angiogenesis. Finally, DCC-2618 was found to downregulate IgE-mediated histamine release from basophils and tryptase release from mast cells. Together, DCC-2618 inhibits growth, survival and activation of multiple cell types relevant to advanced systemic mastocytosis. Whether DCC-2618 is effective in vivo in patients with advanced systemic mastocytosis is currently under investigation in clinical trials.

Drug-induced inhibition of phosphorylation of STAT5 overrides drug resistance in neoplastic mast cells

Systemic mastocytosis (SM) is a mast cell (MC) neoplasm with complex pathology and a variable clinical course. In aggressive SM (ASM) and MC leukemia (MCL) responses to conventional drugs are poor and the prognosis is dismal. R763 is a multi-kinase inhibitor that blocks the activity of Aurora-kinase-A/B, ABL1, AKT and FLT3. We examined the effects of R763 on proliferation and survival of neoplastic MC. R763 produced dose-dependent inhibition of proliferation in the human MC lines HMC-1.1 (IC₅₀ 5-50 nM), HMC-1.2 (IC₅₀ 1-10 nM), ROSA^{KIT WT} (IC₅₀ 1-10 nM), ROSA^{KIT D816V} (IC₅₀ 50-500 nM) and MCPV-1.1 (IC₅₀ 100-1000 nM). Moreover, R763 induced growth inhibition in primary neoplastic MC in patients with ASM and MCL. Growth-inhibitory effects of R763 were accompanied by signs of apoptosis and a G2/M cell cycle arrest. R763 also inhibited phosphorylation of KIT, BTK, AKT and STAT5 in neoplastic MC. The most sensitive target appeared to be STAT5. In fact, tyrosine phosphorylation of STAT5 was inhibited by R763 at 10 nM. At this low concentration, R763 produced synergistic growth-inhibitory effects on neoplastic MC when combined with midostaurin or dasatinib. Together, R763 is a novel promising multi-kinase inhibitor that blocks STAT5 activation and thereby overrides drug-resistance in neoplastic MC.

The clinical and molecular diversity of mast cell leukemia with or without associated hematologic neoplasm

Mast cell leukemia is a rare variant of advanced systemic mastocytosis characterized by at least 20% of mast cells in a bone marrow smear. We evaluated clinical and molecular characteristics of 28 patients with (n=20, 71%) or without an associated hematologic neoplasm. De novo mast cell leukemia was diagnosed in 16 of 28 (57%) patients and secondary mast cell leukemia evolving from other advanced systemic mastocytosis subtypes in 12 of 28 (43%) patients, of which 7 patients progressed while on cytoreductive treatment. Median bone marrow mast cell infiltration was 65% and median serum tryptase was 520 μg/L. C-findings were identified in 26 of 28 (93%) patients. Mutations in KIT (D816V, n=19; D816H/Y, n=5; F522C, n=1) were detected in 25 of 28 (89%) patients and prognostically relevant additional mutations in SRSF2, ASXL1 or RUNX1 (S/A/R^pos) in 13 of 25 (52%) patients. Overall response rate in 18 treatment-naïve patients was 5 of 12 (42%) on midostaurin and 1 of 6 (17%) on cladribine, and after switch 1 of 4 (25%) on midostaurin and 0 of 3 on cladribine, respectively. S/A/R^pos adversely affected response to treatment and progression to secondary mast cell leukemia (n=6) or acute myeloid leukemia (n=3) while on treatment (P<0.05). The median overall survival from mast cell leukemia diagnosis was 17 months as compared to 44 months in a control group of 124 patients with advanced systemic mastocytosis but without mast cell leukemia (P=0.03). In multivariate analyses, S/A/R^pos remained the only independent poor prognostic variable predicting overall survival (P=0.007). In conclusion, the molecular signature should be determined in all patients with mast cell leukemia because of its significant clinical and prognostic relevance.