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

The diagnostic workup for systemic mastocytosis differs from consensus recommendations: Results of a worldwide survey

Objective

Mastocytosis is a complex disorder affecting various organs. The diagnostic workup can be challenging and requires a multidisciplinary approach including the use of uncommon tests. To assess mastocytosis management around the globe, we conducted the first worldwide online survey for physicians.

Methods

A 21-item questionnaire was sent out to the members of the World Allergy Organization (WAO), the Global Allergy and Asthma European Network (GA2LEN), the Urticaria (UCARE) and Angioedema (ACARE) Centers of Reference and Excellence, the German Society of Allergology and Clinical Immunology (DGAKI), and the European Mast Cell and Basophil Research Network (EMBRN) in April-June 2021.

Results

Across 628 respondents from 79 countries 87.7% and 9.7% of physicians were allergists/clinical immunologists and/or dermatologists. Participating physicians were from all regions of the world (Europe, EU: 41.6%; North America, NA: 24.8%; Latin America, LA: 14.5%; Asia-Pacific, AP: 12.6%; and Africa/Middle East, AME: 6.5%). Only 2.2% of respondents worked at Specialized Mastocytosis Centers (SMCs) in North America or European Union. Physicians reported caring for 4 patients with mastocytosis per year, with higher numbers in European Union and Asia Pacific (5/year) compared to Latin America (2/year). Dermatologists and physicians who work at SMCs reported higher patient numbers (15/year and 80/year, respectively). Suspicion of mastocytosis in the allergology and dermatology community is commonly driven by anaphylaxis (82.9%), mastocytosis skin lesions (82.1%), or elevated tryptase levels (76.6%). Osteoporosis and gastrointestinal symptoms less often prompted suspicion of mastocytosis (21.4% and 49.9%, respectively). World Health Organisation (WHO)-diagnostic criteria and classification, regardless of the region, are only used by about 50% of physicians, with higher rates for SMCs (83.3%). Serum tryptase, bone marrow biopsy, and KIT D816V mutation analysis are included in the diagnostic workup by 90.9%, 61.5%, and 58.4% of physicians, respectively. The biggest challenges for the management of mastocytosis are the lack of more effective treatment options (51.1%), missing multidisciplinary networks (47.1%), and the lack of experience of specialists from other disciplines (39.0%).

Conclusions

The diagnostic workup for mastocytosis differs from consensus recommendations and varies between regions. This may be improved by establishing active multidisciplinary networks, increasing access to diagnostic procedures, consistently applying WHO criteria, and developing new Mastocytosis Centers of Reference and Excellence.

Tyrosine Kinase Inhibitors in Non-advanced Systemic Mastocytosis

Systemic mastocytosis is associated with KIT D816V mutation in more than 90% of cases. Patients with non-advanced forms of mastocytosis (indolent systemic mastocytosis, bone marrow mastocytosis, and smoldering systenic mastocytosis) have a low rate of progession to advanced variants and generally have a comparable life expectancy to age-matched general population. Symptomatology in non-advanced mastocytosis is variable and is related to mast cell mediator release. While some patients require no or minimal symptomatic therapy with antimediator drugs, other may suffer from refractory symptoms impacting the quality of life despite being on multiple anti-mediator drugs. KIT tyrosine kinase inhibitors have been approved for advanced SM, and avapritinib has also been recently approved as the first such inhibitor for indolent systemic mastocytosis. Other TKIs are currently in clinical trials for patients with non-advanced SM who have persistent and severe symptoms despite optimized antimediator therapy. This article will review the current state of the science and available clinical data from trials of tyrosine kinase inhibitors in non-advanced systemic mastocytosis.

Genome-Wide DNA Methylation and Gene Expression in Patients with Indolent Systemic Mastocytosis

Mastocytosis is a clinically heterogenous, usually acquired disease of the mast cells with a survival time that depends on the time of onset. It ranges from skin-limited to systemic disease, including indolent and more aggressive variants. The presence of the oncogenic KIT p. D816V gene somatic mutation is a crucial element in the pathogenesis. However, further epigenetic regulation may also affect the expression of genes that are relevant to the pathology. Epigenetic alterations are responsible for regulating the expression of genes that do not modify the DNA sequence. In general, it is accepted that DNA methylation inhibits the binding of transcription factors, thereby down-regulating gene expression. However, so far, little is known about the epigenetic factors leading to the clinical onset of mastocytosis. Therefore, it is essential to identify possible epigenetic predictors, indicators of disease progression, and their link to the clinical picture to establish appropriate management and a therapeutic strategy. The aim of this study was to analyze genome-wide methylation profiles to identify differentially methylated regions (DMRs) in patients with mastocytosis compared to healthy individuals, as well as the genes located in those regulatory regions. Genome-wide DNA methylation profiling was performed in peripheral blood collected from 80 adult patients with indolent systemic mastocytosis (ISM), the most prevalent subvariant of mastocytosis, and 40 healthy adult volunteers. A total of 117 DNA samples met the criteria for the bisulfide conversion step and microarray analysis. Genome-wide DNA methylation analysis was performed using a MethylationEPIC BeadChip kit. Further analysis was focused on the genomic regions rather than individual CpG sites. Co-methylated regions (CMRs) were assigned via the CoMeBack method. To identify DMRs between the groups, a linear regression model with age as the covariate on CMRs was performed using Limma. Using the available data for cases only, an association analysis was performed between methylation status and tryptase levels, as well as the context of allergy, and anaphylaxis. KEGG pathway mapping was used to identify genes differentially expressed in anaphylaxis. Based on the DNA methylation results, the expression of 18 genes was then analyzed via real-time PCR in 20 patients with mastocytosis and 20 healthy adults. A comparison of the genome-wide DNA methylation profile between the mastocytosis patients and healthy controls revealed significant differences in the methylation levels of 85 selected CMRs. Among those, the most intriguing CMRs are 31 genes located within the regulatory regions. In addition, among the 10 CMRs located in the promoter regions, 4 and 6 regions were found to be either hypo- or hypermethylated, respectively. Importantly, three oncogenes-FOXQ1, TWIST1, and ERG-were identified as differentially methylated in mastocytosis patients, for the first time. Functional annotation revealed the most important biological processes in which the differentially methylated genes were involved as transcription, multicellular development, and signal transduction. The biological process related to histone H2A monoubiquitination (GO:0035518) was found to be enriched in association with higher tryptase levels, which may be associated with more aberrant mast cells and, therefore, more atypical mast cell disease. The signal in the BAIAP2 gene was detected in the context of anaphylaxis, but no significant differential methylation was found in the context of allergy. Furthermore, increased expression of genes encoding integral membrane components (GRM2 and KRTCAP3) was found in mastocytosis patients. This study confirms that patients with mastocytosis differ significantly in terms of methylation levels in selected CMRs of genes involved in specific molecular processes. The results of gene expression profiling indicate the increased expression of genes belonging to the integral component of the membrane in mastocytosis patients (GRM2 and KRTCAP3). Further work is warranted, especially in relation to the disease subvariants, to identify links between the methylation status and the symptoms and novel therapeutic targets.

European Competence Network on Mastocytosis (ECNM): 20-Year Jubilee, Updates, and Future Perspectives

In 2002, the European Competence Network on Mastocytosis (ECNM) was launched as a multidisciplinary collaborative initiative to increase the awareness and to improve diagnosis and management of patients with mast cell (MC) disorders. The ECNM consists of a net of specialized centers, expert physicians, and scientists who dedicate their work to MC diseases. One essential aim of the ECNM is to timely distribute all available information about the disease to patients, doctors, and scientists. In the past 20 years, the ECNM has expanded substantially and contributed successfully to the development of new diagnostic concepts, and to the classification, prognostication, and treatments of patients with mastocytosis and MC activation disorders. The ECNM also organized annual meetings and several working conferences, thereby supporting the development of the World Health Organization classification between 2002 and 2022. In addition, the ECNM established a robust and rapidly expanding patient registry and supported the development of new prognostic scoring systems and new treatment approaches. In all projects, ECNM representatives collaborated closely with their U.S. colleagues, various patient organizations, and other scientific networks. Finally, ECNM members have started several collaborations with industrial partners, leading to the preclinical development and clinical testing of KIT-targeting drugs in systemic mastocytosis, and some of these drugs received licensing approval in recent years. All these networking activities and collaborations have strengthened the ECNM and supported our efforts to increase awareness of MC disorders and to improve diagnosis, prognostication, and therapy in patients.

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.

Acute mast cell leukemia without KIT D816V mutation and lack of CD2 and CD25-a case report of rare entity

Systemic mastocytosis (SM) is a rare hematological neoplasm caused by the excessive proliferation of pathological mast cells that accumulate in the bone marrow (BM) and other extracutaneous organs leading to multi-organ damage and failure. Mast cell leukemia (MCL) is a rare form of systemic mastocytosis, accounting for < 1% of all cases of mastocytosis. MCL usually behaves aggressively with poor responses to current treatment options. Here, we report a diagnostic challenge with the leukemic subtype of MCL with a primary suspicion of pancreatic cancer. A cytomorphological, immunophenotypic, and histopathological examination of the bone marrow was performed. The diagnosis was based on the presence of ≥ 20% atypical and immature mast cells in the bone marrow and ≥ 10% mast cells among the peripheral white blood cells. The neoplastic cell population was identified as mast cell lineage by the expression of CD117 and tryptase. Only 3% of neoplastic cells displayed surface markers characteristic for clonal mast cells: CD25 and CD2. The D816V KIT mutation was not found. Neoplastic mast cells expressed CD30, a marker that is currently considered as a new minor criterion for SM. In the presented case, the primary suspicion of pancreatic cancer with osteosclerotic, lung, and pleural metastases was misleading, and a differential diagnosis based on hematological findings was performed. The patient's severe symptoms were likely the result of organ damage from mast cell infiltration. Despite the use of intensive acute myeloid leukemia (AML)-like polychemotherapy, the patient died during the course of post-induction myelosuppression due to bleeding complications.

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.

A Practical Approach to Systemic Mastocytosis Complications in Cardiac Surgery: A Case Report and Systematic Review of the Literature

(1) Background: Systemic mastocytosis is a rare, non-curable disease with potential life-threatening complications in patients receiving cardiac surgery. (2) Methods: This systematic review of the literature was prompted by the case of a life-threatening anaphylactic reaction during cardiac surgery related to systemic mastocytosis. The search of all types of studies, using several databases (Pubmed, Scopus and Web of Science), was conducted through September 2022 to identify the relevant studies. (3) Results: Twelve studies were included describing cases of patients undergoing cardiac surgery who were diagnosed with systemic mastocytosis. An adverse effect, namely anaphylaxis, has happened in three cases. Different strategies of premedication, intraoperative and postoperative management were used. In our case, the patient was admitted for elective biological aortic valve replacement due to severe aortic stenosis. Intraoperatively, the patient developed an anaphylactic shock during the administration of protamine after separation from the cardiopulmonary bypass. This anaphylaxis reaction was a complication of the pre-existing systemic mastocytosis and could be successfully managed by the administration of epinephrine, antihistamines and corticosteroids. (4) Conclusions: This systematic literature search and case report highlight the importance of careful preoperative planning, as well as coordination between cardiac surgeons, anesthesiologists and hemato-oncological specialists, in patients with rare but complication-prone diseases such as systemic mastocytosis.

Comprehensive mastocytosis data analysis from a single center

Mastocytosis is a very rare disorder and is divided into three prognostically distinct variants by World Health Organization: Cutaneous mastocytosis (CM), systemic mastocytosis (SM), and mast cell sarcoma or localized mast cell (MC) tumors. The wide range of complaints may cause patients to consult various clinics, with resulting mis- or underdiagnosis. Therefore, cooperation between different subspecialties is of paramount importance. In this article, we have compiled 104 adult mastocytosis cases diagnosed and followed in our Hematology and other clinics. 86 (82.7%) of 104 patients had systemic mastocytosis. Osteoporosis, disease-related complications, and secondary malignancies are important topics in this group. We know that indolent form has great survival. But smoldering or aggressive mastocytosis has a poor prognosis. CM and indolent SM have a significantly better prognosis compared to aggressive SM (p < 0.001). We found that the presence of more than 25% of mast cells in the bone marrow, the presence of concomitant marrow dysplasia, and the presence of disease-related complications affect survival (p < 0.001). In addition to the WHO classification, the IPSM scoring system is indicative of the prognosis in this rare disease.

Therapeutic management and outcome of patients with advanced systemic mastocytosis treated with midostaurin: A comprehensive real-life study in the French national healthcare database

Advanced Systemic Mastocytosis (Adv-SM) is rare and has a poor prognosis. Midostaurin (Rydapt^® ) is one of the few treatments for Adv-SM in Europe. The study aims were to describe the characteristics of patients treated with midostaurin, their treatment modalities, outcomes, and serious events requiring hospitalization. This retrospective observational study was conducted using the French National Healthcare Database (SNDS) and included adult Adv-SM patients treated with midostaurin between 01-01-2012 and 09-30-2018. Kaplan-Meier method was used to assess survival and treatment duration. Eighty-one patients were included: 37 with Aggressive Systemic Mastocytosis (SM) (46%), 31 with SM with an Associated Hematological Neoplasm (38%), and 4 with Mast Cell Leukemia (5%). The SM subtype was undetermined in 9 patients (11%). The median age was 67 years; 64% of patients were male. Over the mean follow-up of 11.4 months, median midostaurin treatment duration was 8.4 months and 28 patients (35%) were still under treatment at the end of the study. One-year and 5-year overall survival rates estimated since the time of diagnosis were 83% and 56%, respectively. Twelve serious events (among those frequently reported during clinical trials and compassionate use) requiring hospitalization were identified; a causal association with Adv-SM treatment could neither be excluded nor established. In this first real-life study on patients treated with midostaurin for Adv-SM, the patients' characteristics, their management, treatment discontinuation, and survival were in line with previous results (compassionate use and clinical trials).

Systemic Mastocytosis in a Patient with BCR-ABL1-Positive Chronic Myeloid Leukemia in the Remission Phase

Systemic mastocytosis (SM) comprises a group of rare disorders resulting from tissue infiltration by pathological mast cells. In a percentage ranging from 5 to 40% in various patient series, SM appears to be associated with an accompanying hematologic neoplasm (SM-AHN). The coexistence of SM with chronic myelogenous leukemia (CML) is extremely rare with only 3 cases in the literature. The natural course of CML has changed dramatically over the past 2 decades with the use of tyrosine kinase inhibitors (TKIs). We report a case of diagnosing SM in a patient in complete molecular remission of CML after stopping TKI treatment.

Patient-reported outcomes among patients with systemic mastocytosis in routine clinical practice: Results of the TouchStone SM Patient Survey

BACKGROUND

Systemic mastocytosis (SM) is a rare clonal neoplasm driven by KIT D816V and other mutations. Data were collected from the patient perspective on disease burden and included an SM-specific symptom assessment tool.

METHODS

US adults aged 18 years and older with a self-reported SM diagnosis completed an online TouchStone SM Patient Survey of 100 items, including the 12-item Short-Form Health Survey, the Indolent Systemic Mastocytosis Symptom Assessment Form, and the Work Productivity and Activity Impairment Questionnaire, as well as questions about SM diagnosis, the impact of SM on daily activities, work impairment, and health care use. The results were analyzed using descriptive statistics.

RESULTS

Fifty-six individuals completed the survey (89% women; median age, 48 years; mean time since diagnosis, 6.7 years), reporting indolent SM (66%), aggressive SM (9%), smoldering SM (5%), and unknown SM subtype (18%). Over a 1-year recall, respondents reported seeking emergency care for anaphylaxis (30%) and taking three or more prescription medications (52%) for SM. Over one half of patients (54%) reduced their work hours because of SM, and 64% avoided leaving home because of symptoms. A majority of respondents (93%) had experienced ≥10 SM-related symptoms, noting that the most bothersome were anaphylactic episodes (18%), abdominal/stomach pain (16%), diarrhea/loose stools (13%), and fatigue (11%). Whereas an Indolent Systemic Mastocytosis Symptom Assessment Form-derived total symptom score of 28 is used to indicate moderate-to-severe symptoms, the mean total symptom score was 52.7. Mental and physical component summary scores from the 12-item Short-Form Health Survey were below population norms.

CONCLUSIONS

Patients who were surveyed reported substantial symptom burden and unmet needs because of SM, as evidenced by seeking emergency care and reporting bothersome symptoms, poor quality of life, and reduced work hours and productivity.

LAY SUMMARY

The objective of this research was to understand the burden and unmet needs in the rare disease of systemic mastocytosis (SM) to guide future care. Fifty-six patients completed an online survey containing questions about their diagnosis, medications, health care use, quality of life, and SM symptoms. The results demonstrated that SM is associated with severe and burdensome symptoms, anaphylactic events, emergency department visits, use of multiple medications, reduced ability to work, and poor physical and psychological quality of life. These findings suggest the need for future advances to address unmet needs in patients affected by SM.

Avapritinib for advanced systemic mastocytosis

Avapritinib, a highly selective inhibitor of KIT D816V, was approved by the Food and Drug Administration in 2021 for treatment of advanced systemic mastocytosis (AdvSM) and by the European Medicines Agency in 2022 for AdvSM after prior systemic therapy. The phase 1 EXPLORER and phase 2 PATHFINDER trials demonstrated that avapritinib can elicit complete and durable clinical responses and molecular remission of KIT D816V. Key management challenges relate to the complex mutational landscape of AdvSM, often found with an associated hematologic neoplasm.

How persons with systemic mastocytosis describe the time between symptom onset and receiving diagnosis

AIM

The aim of the study was to explore how persons with systemic mastocytosis (SM) described the time between the onset of symptoms and signs and getting the diagnosis.

BACKGROUND

SM is a rare disease caused by the accumulation of clonal mast cells with abnormal function. The symptoms and signs of the disease are varied, often diffuse and affect individuals differently. Due to this complexity, a multi-disciplinary diagnostic approach is required, in which general practitioners play an important part in identifying and referring patients relevant for such investigations.

METHODS

Sixteen persons with SM were interviewed about their experiences of the time before the diagnosis was received. Systematic text condensation was used in the analysis process.

FINDINGS

The time between symptom and signs onset and diagnosis was perceived as difficult. SM often had a complex and unpredictable effect on a person's daily life, long before diagnosis. In the analysis, three themes were found. Having symptoms and signs with an unknown cause included the participants' descriptions of numerous symptoms and signs, often years before diagnosis. These could be severe and result in worries for both participants and their next-of-kin. Dealing with the symptoms and signs encompassed the different ways in which the participants coped with the symptoms and signs, and sought relief. Being a patient without a diagnosis underlined the lack of information and knowledge within healthcare, often resulting in a delayed or incorrect diagnosis. The study highlighted the importance of a person-centred approach and the need to increase knowledge of the disease within primary care, to shorten this stressful and vulnerable time.

Mast Cell Diseases in Practice and Research: Issues and Perspectives Raised by Patients and Their Recommendations to the Scientific Community and Beyond

BACKGROUND

Since 2010, patients and physicians have collaborated to understand unmet needs of patients with mast cell diseases, incorporating mastocytosis and mast cell activation disorders, which include mast cell activation syndromes.

OBJECTIVE

This Open Innovation in Science project aims to expand understanding of the needs of patients affected by mast cell diseases, and encourage global communication among patient advocacy groups, physicians, researchers, industry, and government. A major aim is to support the scientific community's efforts to improve diagnosis, management, therapy, and patients' quality of life by addressing unmet needs.

METHODS

In collaboration with mast cell disease specialists, 13 patient advocacy groups from 12 countries and regions developed lists of top patient needs. A core team of leaders from patient advocacy groups collected and analyzed the data and proposed possible actions to address patient needs.

RESULTS

Findings identified similarities and differences among participating countries in unmet needs between patients with mastocytosis and those with mast cell activation syndromes. Issues emphasized struggles relating to the nature and rarity of mast cell diseases, their impact on quality of life, the diagnostic process, access to appropriate care, more effective treatment, and the need for research.

CONCLUSIONS

Solutions vary across countries because situations differ, in particular regarding the existence of and access to centers of excellence and reference centers. Multifaceted mast cell activation syndrome barriers necessitate innovative approaches to improve access to appropriate care. The outcomes of this project should greatly support scientists and clinicians in their efforts to improve diagnosis, management, and treatment of patients with mastocytosis and mast cell activation disorders.

Tyrosine kinase inhibitors for the treatment of indolent systemic mastocytosis: are we there yet?

Indolent systemic mastocytosis (ISM) is the most prevalent form of systemic mastocytosis. Many patients with ISM suffer from mast cell (MC) mediator-related symptoms In a small number of patients, hematologic progression is seen in the follow up. In some patients with ISM, symptoms arising from MC-derived mediators including gastrointestinal symptoms, anaphylaxis, neuropsychiatric symptoms are kept under control with conventional mediator-targeting drugs or MC-stabilizing agents. However, in a substantial number of patients, the symptoms are refractory to such conventional therapy. For these patients, novel drugs and targeted approaches are considered. One reasonable approach may be to apply tyrosine kinase inhibitors directed against KIT and other key kinase targets expressed in neoplastic MC in ISM. Since MC in over 90% of all patients with typical ISM display the KIT D816V mutant receptor, clinically effective KIT-targeting drugs have to be active against this mutant form of KIT. The two such most effective and well-studied agents currently available are midostaurin and avapritinib. Other KIT-targeting drugs, such as imatinib or masitinib, are less effective or even non-effective against KIT D816V and are thus only recommended for use in patients with other KIT mutant forms (non codon 816 mutations) or with wild type KIT. In the present article, we review the current state in the treatment of ISM with tyrosine kinase inhibitors, with special emphasis on treatment responses and potential adverse effects. In fact, all of these agents also have unique and common adverse effects, and their use to treat ISM patients should be balanced against their toxicity and short and long term safety.

Evaluation and Classification of Mast Cell Disorders: A Difficult to Manage Pathology in Clinical Practice

Mast cells are granulocytic immunomodulatory cells with an important role in physiologic and pathogenic processes due to their location at the junction between the internal and external environment and to their capacity to release a broad range of active mediators. Mast cells mediators have both pro-inflammatory and anti-inflammatory activities and are implicated in various and complex pathology. Mast cells disorders (MCDs) represent a heterogeneous pathology, with frequently difficult and challenging evaluation and diagnostic workup. MCDs can be primary, secondary to other diseases, or idiopathic. Increased research interest in this field was noted during the last decade and various classification criteria, as well as diagnostic and treatment recommendations, were proposed. The aim of this paper is to review the most recent published data on the classification and evaluation of mast cells disorders and to point out the main difficulties in diagnosing and managing these complex diseases in medical practice.

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.

DNA methylation profile in patients with indolent systemic mastocytosis

BACKGROUND

Mastocytosis is a clinically heterogeneous, usually acquired disease of the mast cells with a survival time that depends on the onset of the disease and ranges from skin-limited to systemic disease, including indolent and more aggressive variants. The crucial element in pathogenesis is the presence of oncogenic KIT somatic mutation D816V. Further epigenetic alterations are responsible for regulating the expression of genes. It is essential to identify indicators of disease progression, and the specific clinical picture to establish an appropriate therapeutic strategy.

OBJECTIVE

The aim of this study was to analyze the relation of mastocytosis symptoms and epigenetic changes, and to identify epigenetic predictors of the disease.

METHODS

Global DNA methylation profile analysis was performed in peripheral blood collected from 73 patients with indolent systemic mastocytosis (ISM) and 43 healthy adult volunteers. Levels of 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) were determined using an ELISA-based method, while the methylation of the Alu and LINE-1 repeats were assayed with the quantitative methylation-specific PCR technique. A questionnaire interview was conducted among the study participants to collect data on possible epigenetic modifiers. Additionally, the methylation profile was compared between three human mast cell lines: ROSA KIT D816V, ROSA KIT WT, and HMC-1.1 KIT V560G, in order to assess the association between KIT mutations and methylation profile.

RESULTS

A significantly lower level of DNA hydroxymethylation (5-hmC) in the blood was found in patients with ISM as compared to the controls (0.022% vs. 0.042%, p = 0.0001). Differences in the markers of global DNA methylation (5-mC, Alu, LINE-1) were not statistically significant, although they did indicate generally higher DNA methylation in patients with mastocytosis. The 5-hmC level was significantly associated with allergy (p = 0.011) in patients with ISM, showing a higher level of 5-hmC in patients with allergy as compared to patients without allergy. The in vitro study revealed significant differences between the studied cell lines at the level of 5-mC, Alu, and LINE-1.

CONCLUSIONS

This study confirms that epigenetic changes are involved in mastocytosis, and suggests that allergy may be an important epigenetic modifier of the disease. A possible association between KIT mutations and methylation status observed in human mast cell lines requires further investigation in human studies.

CLINICAL IMPLICATIONS

Epigenetic alterations are involved in mastocytosis pathology. The possible role of allergy as an important epigenetic modifier suggests the more impaired function of mast cells in ISM patients without allergy.

CAPSULE SUMMARY

Decreased DNA demethylation in the blood DNA of patients with ISM confirms that epigenetic alterations are involved in mastocytosis pathology. We observed a possible role of allergy as an important epigenetic modifier. There is a possible association between KIT mutations and the methylation status observed in human mast cell lines.

Case report of a clinically indolent but morphologically high-grade cutaneous mast cell tumor in an adult: Atypical cutaneous mastocytoma or mast cell sarcoma?

We present a case of an adult male with a solitary mast cell tumor of the skin with unusual nuclear pleomorphism and mitotic activity. The tumor was excised, recurred within 2 years, was reexcised after 4 years and did not recur >6 years after diagnosis. The tumor showed progressive cytonuclear atypia and a high mitotic and proliferation rate by Ki67-staining from the onset. No KIT mutations were identified in the tumor and bone marrow. Serum tryptase levels and a bone marrow aspirate and trephine biopsy were normal. Although the histomorphology of the skin tumor was consistent with mast cell sarcoma, the clinical behavior without systemic progression argued against this diagnosis. The tumor was finally considered as atypical mastocytoma, borderline to mast cell sarcoma. Currently, the patient is in close follow-up and still in complete remission.

Small intestinal immunopathology and GI-associated antibody formation in hereditary alpha-tryptasemia

BACKGROUND

Hereditary alpha-tryptasemia (HαT) is characterized by elevated basal serum tryptase due to increased copies of the TPSAB1 gene. Individuals with HαT frequently present with multisystem complaints, including anaphylaxis and seemingly functional gastrointestinal (GI) symptoms.

OBJECTIVE

We sought to determine the prevalence of HαT in an irritable bowel syndrome cohort and associated immunologic characteristics that may distinguish patients with HαT from patients without HαT.

METHODS

Tryptase genotyping by droplet digital PCR, flow cytometry, cytometry by time-of-flight, immunohistochemistry, and other molecular biology techniques was used.

RESULTS

HαT prevalence in a large irritable bowel syndrome cohort was 5% (N = 8/158). Immunophenotyping of HαT PBMCs (N ≥ 27) revealed increased total and class-switched memory B cells. In the small bowel, expansion of tissue mast cells with expression of CD203c, HLA-DR, and FcεRI, higher intestinal epithelial cell pyroptosis, and increased class-switched memory B cells were observed. IgG profiles in sera from individuals with HαT (N = 21) significantly differed from those in individuals with quiescent Crohn disease (N = 20) and non-HαT controls (N = 19), with increased antibodies directed against GI-associated proteins identified in individuals with HαT.

CONCLUSIONS

Increased mast cell number and intestinal epithelial cell pyroptosis in the small intestine, and class-switched memory B cells in both the gut and peripheral blood associated with IgG reactive to GI-related proteins, distinguish HαT from functional GI disease. These innate and adaptive immunologic findings identified in association with HαT are suggestive of subclinical intestinal inflammation in symptomatic individuals.

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 Skin Lesions in Mastocytosis: A Multicenter Study of the European Competence Network on Mastocytosis

Mastocytosis is a rare neoplasm characterized by the expansion and accumulation of mast cells in various organ systems. Systemic mastocytosis (SM) may or may not present with cutaneous lesions. To examine the frequency and clinical impact of cutaneous involvement, data on 1,510 patients with mastocytosis collected in the registry of the European Competence Network on Mastocytosis were analyzed. Cutaneous involvement was found in 1,195 of 1,510 patients (79.1%). Of these, 286 had cutaneous mastocytosis, and 721 had SM with skin involvement. Adult patients with skin involvement who did not have a bone marrow examination (n = 188) were defined as having mastocytosis in the skin. In 315 patients, SM without skin involvement was found. The percentage of cases with cutaneous involvement was higher in indolent SM (100%) and smoldering SM (87.9%) compared to aggressive SM (46.8%) or mast cell leukemia (38.5%). After a median follow-up of 5.6 years, no patient with cutaneous mastocytosis had died, but 2.6% of the patients with mastocytosis in the skin, 5.7% of the patients with SM with skin involvement, and 28.95% of the patients with SM without skin involvement had died. Overall survival was longer in patients with skin involvement (cutaneous mastocytosis and/or mastocytosis in the skin and/or SM with skin involvement) than in patients with SM without skin involvement (P < 0.0001). These data argue for a thorough examination of both the skin and bone marrow in adult 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.

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.

Systemic Mastocytosis: A Rare Cause of Diarrhea

Mastocytosis is a spectrum of neoplastic, clonal cell disorders that are characterized by mast cell hyperplasia and accumulation. Disease and clinical presentation can vary depending on the extent of spread, ranging from skin-limited cutaneous mastocytosis to systemic mastocytosis that can mimic other disease processes. Symptoms may include pruritus, flushing, hypotension, headaches, abdominal pain, nausea, vomiting, and diarrhea. Although gastrointestinal (GI) symptoms are present in a majority of patients with systemic disease, the actual percentage of gut mast cell infiltration remains unknown. Here we describe a case of diarrhea secondary to GI involvement of systemic mastocytosis. A 55-year-old woman with a known history of systemic mastocytosis and medical noncompliance complained of persistent chronic diarrhea for one year. She was evaluated for other causes of diarrhea but all additional testing was unrevealing. She ultimately underwent upper endoscopy and colonoscopy in which biopsy and histologic analysis confirmed the presence of mastocyte infiltration. She was restarted on her medical therapy and her symptoms resolved. In conclusion, systemic mastocytosis is an uncommon cause of chronic diarrhea. However, in select patients, it is important to obtain a thorough medical history and exclude other potential causes.

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.

New developments in diagnosis, prognostication, and treatment of advanced systemic mastocytosis

Systemic mastocytosis (SM) has greatly benefited from the broad application of precision medicine techniques to hematolymphoid neoplasms. Sensitive detection of the recurrent KIT D816V mutation and use of next-generation sequencing (NGS) panels to profile the genetic landscape of SM variants have been critical adjuncts to the diagnosis and subclassification of SM, and development of clinical-molecular prognostic scoring systems. Multilineage KIT involvement and multimutated clones are characteristic of advanced SM (advSM), especially SM with an associated hematologic neoplasm (AHN). A major challenge is how to integrate conventional markers of mast cell disease burden (percentage of bone marrow mast cell infiltration and serum tryptase levels) with molecular data (serial monitoring of both KIT D816V variant allele frequency and NGS panels) to lend more diagnostic and prognostic clarity to the heterogeneous clinical presentations and natural histories of advSM. The approval of the multikinase/KIT inhibitor midostaurin has validated the paradigm of KIT inhibition in advSM, and the efficacy and safety of second-generation agents, such as the switch-control inhibitor ripretinib (DCC-2618) and the D816V-selective inhibitor avapritinib (BLU-285) are being further defined in ongoing clinical trials. Looking forward, perhaps the most fruitful marriage of the advances in molecular genetics and treatment will be the design of adaptive basket trials that combine histopathology and genetic profiling to individualize treatment approaches for patients with diverse AHNs and relapsed/refractory SM.

New developments in the field of mastocytosis and mast cell activation syndromes: a summary of the Annual Meeting of the European Competence Network on Mastocytosis (ECNM) 2019

Mastocytosis are a group of hematologic neoplasms characterized by an accumulation of atypical mast cells in one or several organs/tissues, often accompanied by mast cell activation. Whereas in children the disease manifestations are mostly limited to the skin, in adults the disease is usually systemic (systemic mastocytosis; SM) and involves the bone marrow and/or other internal organs. Several variants of SM have been defined. Whereas most patients have indolent SM, some patients have advanced SM, which underlines the complexity of SM. In 2002, a European consortium of clinicians and scientists initiated a multidisciplinary, multi-national cooperative network, termed the 'European Competence Network on Mastocytosis' (ECNM), with the aim to improve diagnosis and therapy of patients with mastocytosis and other mast cell activation disorders. Since then, members of the ECNM have organized Annual Meetings in several European countries. The present article provides a summary of advances in the field presented during the 17th Annual ECNM meeting held in Salzburg in October 2019.

The Spectrum of Aggressive Mastocytosis: A Workshop Report and Literature Review

Most cases of mastocytosis are indolent, usually cutaneous mastocytosis or indolent systemic mastocytosis (SM). Aggressive mast cell (MC) diseases are very rare and often fatal. They can develop de novo or due to progression of indolent forms and can present in different ways; either as MC sarcoma or as advanced SM which includes aggressive SM, MC leukemia, and SM with an associated hematological neoplasm. This review will describe these different aggressive forms of mastocytosis, illustrated by cases submitted to the workshop of the 18th Meeting of the European Association for Haematopathology, Basel 2016, organized by the European Bone Marrow Working Group. In addition, the diagnostic criteria for identifying myelomastocytic leukemia, an aggressive myeloid neoplasm with partial MC differentiation that falls short of the criteria for SM, and disease progression in patients with established mastocytosis are discussed.

Prognostic impact of eosinophils in mastocytosis: analysis of 2350 patients collected in the ECNM Registry

Systemic mastocytosis (SM) is frequently associated with eosinophilia. To examine its prevalence and clinical impact in all WHO classification-based subcategories, we analyzed eosinophil counts in 2350 mastocytosis patients using the dataset of the European Competence Network on Mastocytosis. Ninety percent of patients had normal eosinophil counts, 6.8% mild eosinophilia (0.5-1.5 × 10⁹/l), and 3.1% hypereosinophilia (HE; >1.5 × 10⁹/l). Eosinophilia/HE were mainly present in patients with advanced SM (17%/19%), and only rarely recorded in patients with indolent and smoldering SM (5%/1%), and some patients with cutaneous mastocytosis. The eosinophil count correlated with organomegaly, dysmyelopoiesis, and the WHO classification, but not with mediator-related symptoms or allergy. Eosinophilia at diagnosis had a strong prognostic impact (p < 0.0001) on overall survival (OS) and progression-free survival (PFS), with a 10-year OS of 19% for patients with HE, 70% for those with mild eosinophilia, and 88% for patients with normal eosinophil counts. In 89% of patients with follow-up data (n = 1430, censored at start of cytoreductive therapy), eosinophils remained stable. In those with changing eosinophil counts (increase/decrease or mixed pattern), OS and PFS were inferior compared with patients with stable eosinophil counts. In conclusion, eosinophilia and HE are more prevalent in advanced SM and are predictors of a worse 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.

Multidisciplinary Challenges in Mastocytosis and How to Address with Personalized Medicine Approaches

Mastocytosis is a hematopoietic neoplasm defined by abnormal expansion and focal accumulation of clonal tissue mast cells in various organ-systems. The disease exhibits a complex pathology and an equally complex clinical behavior. The classification of the World Health Organization (WHO) divides mastocytosis into cutaneous forms, systemic variants, and localized mast cell tumors. In >80% of patients with systemic mastocytosis (SM), a somatic point mutation in KIT at codon 816 is found. Whereas patients with indolent forms of the disease have a normal or near-normal life expectancy, patients with advanced mast cell neoplasms, including aggressive SM and mast cell leukemia, have a poor prognosis with short survival times. In a majority of these patients, multiple somatic mutations and/or an associated hematologic neoplasm, such as a myeloid leukemia, may be detected. Independent of the category of mastocytosis and the serum tryptase level, patients may suffer from mediator-related symptoms and/or osteopathy. Depending on the presence of co-morbidities, the symptomatology in such patients may be mild, severe or even life-threatening. Most relevant co-morbidities in such patients are IgE-dependent allergies, psychiatric, psychological or mental problems, and vitamin D deficiency. The diagnosis and management of mastocytosis is an emerging challenge in clinical practice and requires vast knowledge, a multidisciplinary approach, and personalized medicine procedures. In this article, the current knowledge about mastocytosis is reviewed with special emphasis on the multidisciplinary aspects of the disease and related challenges in daily practice.