Practical management of adverse events in patients with advanced systemic mastocytosis receiving midostaurin

INTRODUCTION

Systemic mastocytosis (SM) is characterized by the overproduction and accumulation of neoplastic mast cells (MCs) in the bone marrow, skin, and visceral organs. The KIT D816V mutation is found in approximately 90% of cases. In advanced SM (advSM), inferior survival often relates to MC-induced organ damage that may impact multiple organ systems. In addition, mediator symptoms related to MC activation can severely impact the quality of life. The oral multikinase/KIT inhibitor midostaurin was approved by the US Food and Drug Administration and the European Medicines Agency as monotherapy for advSM based on data from phase 2 clinical studies.

AREAS COVERED

This review discusses the management of common adverse events (AEs) in patients with advSM who participated in phase 2 clinical studies that led to the approval of midostaurin.

EXPERT OPINION

In the advSM population undergoing treatment with midostaurin, treatment-related AEs are often difficult to distinguish from disease-related symptoms, which can lead to premature discontinuation and improper dose reduction of midostaurin therapy in patients who might have benefitted from continued therapy. Here we present strategies to help optimize AE management and maximize the potential benefits of midostaurin in advSM.

Detection of the KITD816V mutation in myelodysplastic and/or myeloproliferative neoplasms and acute myeloid leukemia with myelodysplasia-related changes predicts concurrent systemic mastocytosis

Greater than 90% of cases of systemic mastocytosis (SM) harbor pathogenic KIT mutations, particularly KIT^D816V. Prognostically-significant pathogenic KIT mutations also occur in 30-40% of core binding factor-associated acute myeloid leukemia (CBF-AML), but are uncommonly associated with concurrent SM. By comparison, the occurrence of SM in other myeloid neoplasms bearing pathogenic KIT mutations, particularly those with a chronic course, is poorly understood. Review of clinical next-generation sequencing (NGS) performed at our institutions in patients with known or suspected hematologic malignancies over an 8-year period revealed 64 patients with both a pathogenic KIT mutation detected at one or more timepoints and available bone marrow biopsy materials. Patients with KIT^D816V-mutated myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), or overlap MDS/MPN (n = 22) accounted for approximately one-third of our cohort (34%). Comprehensive morphologic and immunophenotypic characterization revealed that nearly all cases (n = 20, 91%) exhibited concurrent SM. In contrast, of the 18 patients (28%) with AML and KIT^D816V, only eight (44%) showed evidence of SM at any point in their disease course (p = 0.0021); of these eight, the AML component was characterized as AML with myelodysplasia-related changes (AML-MRC) in all but one instance (n = 7, 87%). Twelve patients (19%) had pathogenic KIT mutations other than p.D816V, all in the setting of AML (CFB-AML, n = 7; AML, not otherwise specified, n = 2; AML-MRC, n = 1; acute promyelocytic leukemia, n = 1); only two of these patients (17%), both with CBF-AML, exhibited concurrent SM. The remaining 12 patients (19%) had SM without evidence of an associated hematological neoplasm (AHN). For nearly one-third of the 30 SM-AHN patients in our cohort (n = 9, 30%), the SM component of their disease was not initially clinicopathologically recognized. We propose that identification of the KIT^D816V mutation in patients diagnosed with MDS, MPN, MDS/MPN, or AML-MRC should trigger reflex testing for SM.

Long-term Remission of Acute Myeloid Leukemia Developed From Systemic Mastocytosis by Conventional Chemotherapy

Systemic mastocytosis (SM) is a disorder characterized by abnormal proliferation of mast cells with KIT mutations, especially in codon 816. The prognosis of patients developing acute myeloid leukemia (AML) from SM is extremely poor, and hematopoietic cell transplantation is recommended. Herein, we describe a case of an 8-year-old female diagnosed with SM developing AML. A KIT M541L variant in SM was identified in leukemic cells, normal hematopoietic cells, and buccal mucosal cells, suggesting a germline polymorphism. The patient has remained in complete remission for 39 months after completion of chemotherapy. SM developing AML without a KIT D816 mutation may be not necessarily associated with a poor prognosis.

MDS with 5q deletion and rare cKIT positive mastocytosis: a diagnostic and therapeutic challenge

A patient with a diagnosis of myelodysplastic syndrome (MDS) with isolated 5q deletion underwent repeat bone marrow biopsy to assess haematological response after 6 months of initial lenalidomide therapy. Subsequent bone marrow biopsies revealed persistent MDS with del(5q) in addition to a small atypical mast cell population with >25% of mast cells with spindle-shaped morphology and immunohistochemistry characteristics consistent with mastocytosis. Molecular testing on the bone marrow was positive for cKIT D816V and the patient was diagnosed with systemic mastocytosis (SM) with an associated haematological neoplasm. MDS with SM is well known to be associated; however, to the best of our knowledge, only one prior case report identifies MDS with del(5q) and associated cKIT D816V positive mastocytosis. While the exact clonal origin of both chromosomal aberrations is unclear, this case illustrates the therapeutic efficacy of lenalidomide in a patient with MDS with del(5q) and rarely associated cKIT positive SM.

Acute Myeloid Leukemia with Occult Systemic Mastocytosis or Atypical Mast Cells Post-induction

Systemic mastocytosis (SM) is a state of disease that is related to the clonal, neoplastic proliferation of mast cells. Patients who present with SM-Acute Myeloid Leukemia (AML) often have the worst outcome. We present a case of an 18-year-old female who was diagnosed with AML (FLT3 (Fms like tyrosine kinase 3) and PML-RARA (promyelocytic leukemia-retinoic acid receptor alpha) translocation-negative) and after initial treatment with a standard induction regimen of cytarabine and daunorubicin (3+7 regimen), her bone marrow showed blast cells less than 5% and dense aggregates/sheets of atypical/immature mast cells with immunohistochemical stain CD117+ve and toluidine blue positive in mast cell aggregates. Mastocytosis is a clonal neoplastic proliferation of mast cells that accumulate in one or more organ system. Therefore, it is essential to diagnose systemic mastocytosis, particularly in patients of hematological neoplasms.

Mast Cell Activation and KSHV Infection in Kaposi Sarcoma

Purpose: Kaposi sarcoma (KS) is a vascular tumor initiated by infection of endothelial cells (ECs) with KS-associated herpesvirus (KSHV). KS is dependent on sustained proinflammatory signals provided by intralesional leukocytes and continued infection of new ECs. However, the sources of these cytokines and infectious virus within lesions are not fully understood. Here, mast cells (MCs) are identified as proinflammatory cells within KS lesions that are permissive for, and activated by, infection with KSHV.Experimental Design: Three validated MC lines were used to assess permissivity of MCs to infection with KSHV and to evaluate MCs activation following infection. Biopsies from 31 AIDS-KS cases and 11 AIDS controls were evaluated by IHC for the presence of MCs in KS lesions and assessment of MC activation state and infection with KSHV. Plasma samples from 26 AIDS-KS, 13 classic KS, and 13 healthy adults were evaluated for levels of MC granule contents tryptase and histamine.Results: In culture, MCs supported latent and lytic KSHV infection, and infection-induced MC degranulation. Within KS lesions, MCs were closely associated with spindle cells. Furthermore, MC activation was extensive within patients with KS, reflected by elevated circulating levels of tryptase and a histamine metabolite. One patient with clinical signs of extensive MC activation was treated with antagonists of MC proinflammatory mediators, which resulted in a rapid and durable regression of AIDS-KS lesions.Conclusions: Using complimentary in vitro and in vivo studies we identify MCs as a potential long-lived reservoir for KSHV and a source of proinflammatory mediators within the KS lesional microenvironment. In addition, we identify MC antagonists as a promising novel therapeutic approach for KS. Clin Cancer Res; 24(20); 5085-97. ©2018 AACR.

Targeted Treatment Options in Mastocytosis

Mastocytosis refers to a heterogeneous group of disorders resulting from the clonal proliferation of abnormal mast cells and their accumulation in the skin (cutaneous mastocytosis when only in the skin, CM) or in various organs (systemic mastocytosis, SM). This leads to a wide variety of clinical manifestations resulting from excessive mediator release in CM and benign forms of SM (indolent SM, ISM) and from tissue mast cell infiltration causing multiorgan dysfunction and failure in more aggressive subtypes (aggressive SM, ASM, or mast cell leukemia). In addition, SM may be associated with hematological neoplasms (AHN). While treatment of ISM primarily aims at symptom management with anti-mediator therapies, cytoreductive and targeted therapies are needed to control the expansion of neoplastic mast cells in advanced forms of SM, in order to improve overall survival. Mast cell accumulation results from a gain-of-function mutation (mostly the D816V mutation) within the KIT tyrosine kinase domain expressed by mast cells and additional genetic and epigenetic mutations may further determine the features of the disease (ASM and AHN). Consequently, tyrosine kinase inhibitors and targeted therapies directed against the oncogenic signaling machinery downstream of KIT are attractive therapeutic approaches. A better understanding of the relative contribution of these genetic and epigenetic events to the molecular pathogenesis of mastocytosis is of particular interest for the development of targeted therapies and therefore to better choose patient subgroups that would best benefit from a given therapeutic strategy.

A 26-Year-Old Female with Systemic Mastocytosis with Associated Myeloid Neoplasm with Eosinophilia and Abnormalities of PDGFRB, t(4;5)(q21;q33)

Various translocations involving the PDGFRB gene are identified in myeloid neoplasms. However, the PRKG2/PDGFRB fusion gene associated with t(4;5)(q21;q33) has previously been reported in only 3 patients. We present the case of a 26-year-old woman with microcytic anemia, basophilia, thrombocytosis, and massive splenomegaly, who was found to have systemic mastocytosis and associated clonal hematological non-mast cell lineage disease (SM-AHNMD), with myeloid neoplasm with PRKG2/PDGFRB rearrangement. Initial findings included basophilia (37%, 4.1 k/μL), hypercellular marrow with eosinophilia, and increased and atypical megakaryocytes, suggestive of myeloproliferative neoplasm. Additional studies revealed large clusters of CD25 positive mast cells, fulfilling the criteria for the diagnosis of systemic mastocytosis. Consistent with prior reports of this translocation, our patient has responded well to imatinib. This case, in conjunction with others in the literature, suggests a possible connection between t(4;5)(q21;q33) PRKG2/PDGFRB and systemic mastocytosis and highlights their favorable response to imatinib.

Prevalence, pathogenesis, and treatment options for mastocytosis-related osteoporosis

Mastocytosis is a rare condition characterized by abnormal mast cell proliferation and a broad spectrum of manifestations, including various organs and tissues. Osteoporosis is one of the most frequent manifestations of systemic mastocytosis, particularly in adults. Osteoporosis secondary to systemic mastocytosis is a cause of unexplained low bone mineral density that should be investigated when accompanied by suspicious clinical elements. Bone involvement is often complicated by a high recurrence of fragility fractures, mainly vertebral, leading to severe disability. The mechanism of bone loss is the result of different pathways, not yet fully discovered. The main actor is the osteoclast with a relative or absolute predominance of bone resorption. Among the stimuli that drive osteoclast activity, the most important one seems to be the RANK-RANKL signaling, but also histamine and other cytokines play a significant role in the process. The central role of osteoclasts made bisphosphonates, as anti-resorptive drugs, the most rational treatment for bone involvement in systemic mastocytosis. There are a few small studies supporting this approach, with large heterogeneity of drug and administration scheme. Currently, zoledronate has the best evidence in terms of gain in bone mineral density and bone turnover suppression, two surrogate markers of anti-fracture efficacy.

Shared clonal cytogenetic abnormalities in aberrant mast cells and leukemic myeloid blasts detected by single nucleotide polymorphism microarray-based whole-genome scanning

Systemic mastocytosis (SM) is characterized by a clonal proliferation of aberrant mast cells within extracutaneous sites. In a subset of SM cases, a second associated hematologic non-mast cell disease (AHNMD) is also present, usually of myeloid origin. Polymerase chain reaction and targeted fluorescence in situ hybridization studies have provided evidence that, in at least some cases, the aberrant mast cells are related clonally to the neoplastic cells of the AHNMD. In this work, a single nucleotide polymorphism microarray (SNP-A) was used to characterize the cytogenetics of the aberrant mast cells from a patient with acute myeloid leukemia and concomitant mast cell leukemia associated with a KIT D816A mutation. The results demonstrate the presence of shared cytogenetic abnormalities between the mast cells and myeloid blasts, as well as additional abnormalities within mast cells (copy-neutral loss of heterozygosity) not detectable by routine karyotypic analysis. To our knowledge, this work represents the first application of SNP-A whole-genome scanning to the detection of shared cytogenetic abnormalities between the two components of a case of SM-AHNMD. The findings provide additional evidence of a frequent clonal link between aberrant mast cells and cells of myeloid AHNMDs, and also highlight the importance of direct sequencing for identifying uncommon activating KIT mutations.

KIT mutation analysis in mast cell neoplasms: recommendations of the European Competence Network on Mastocytosis

Although acquired mutations in KIT are commonly detected in various categories of mastocytosis, the methodologies applied to detect and quantify the mutant type and allele burden in various cells and tissues are poorly defined. We here propose a consensus on methodologies used to detect KIT mutations in patients with mastocytosis at diagnosis and during follow-up with sufficient precision and sensitivity in daily practice. In addition, we provide recommendations for sampling and storage of diagnostic material as well as a robust diagnostic algorithm. Using highly sensitive assays, KIT D816V can be detected in peripheral blood leukocytes from most patients with systemic mastocytosis (SM) that is a major step forward in screening and SM diagnosis. In addition, the KIT D816V allele burden can be followed quantitatively during the natural course or during therapy. Our recommendations should greatly facilitate diagnostic and follow-up investigations in SM in daily practice as well as in clinical trials. In addition, the new tools and algorithms proposed should lead to a more effective screen, early diagnosis of SM and help to avoid unnecessary referrals.

Mast cells in systemic mastocytosis have distinctly brighter CD45 expression by flow cytometry

OBJECTIVES

We sought to determine the significance of bright CD45 expression on mast cells in cases of systemic mastocytosis vs mast cells in bone marrows uninvolved by systemic mastocytosis and compare this CD45 expression with CD25 and CD2 expression on mast cells.

METHODS

Multiparameter flow cytometry was performed on 31 cases of systemic mastocytosis and 70 bone marrow cases that were not involved by systemic mastocytosis. Bright expression of CD45 was defined as more than 20% of CD117+ mast cells showing brighter CD45 expression than the average expression level of lymphocytes.

RESULTS

Mast cells with bright CD45 expression were seen in 26 systemic mastocytosis cases and three bone marrows uninvolved by systemic mastocytosis (sensitivity, 84%; specificity, 96%). CD25 alone had a greater sensitivity (100%) but lower specificity (93%) compared with bright CD45 for identifying abnormal mast cells, while CD2 alone had lower sensitivity but higher specificity. To reach a specificity of 100%, CD25 together with bright CD45 on mast cells was the optimal combination to detect cases of systemic mastocytosis.

CONCLUSIONS

A combination of bright CD45 and CD25 appears to specifically identify abnormal mast cells in cases of systemic mastocytosis. Further studies will be necessary to confirm these results.

Current treatment options in patients with mastocytosis: status in 2015 and future perspectives

Mastocytosis is a term referring to a heterogeneous group of disorders characterized by abnormal mast cell (MC) accumulation in the skin and/or internal organs. In children, the disease involves mostly the skin (cutaneous mastocytosis; CM), whereas in adults, the disease is usually systemic (systemic mastocytosis; SM). Advanced SM variants with end-organ damage and reduced life expectancy have also been described, but are rare. Clinical signs and symptoms in SM result from excessive mediator release by MCs and, in aggressive forms, from organ failure related to MC infiltration. As a consequence, treatment of indolent SM aims primarily at the control of symptoms caused by MC mediator release. By contrast, in advanced SM, such as aggressive SM, MC leukemia, and MC sarcoma, intensive (chemo)therapy with or without allogeneic stem cell transplantation has to be considered. In addition, activating mutations in KIT (mostly KIT D816V in adults) are found in most patients with SM, so that targeted therapies aimed at blocking mutant KIT variants or/and downstream signaling pathways are currently being developed. Other targets, such as specific surface antigens expressed on neoplastic MCs, might be considered for the development of future therapies in advanced SM.

Modelling of a genetically diverse evolution of Systemic Mastocytosis with Chronic Myelomonocytic Leukemia (SM-CMML) by Next Generation Sequencing

Background

Systemic mastocytosis (SM) is a heterogenous, clonal mast cell (MC) proliferation, rarely associated with clonal hematologic non-mast cell lineage disease (SM-AHNMD). KIT^D816V is regarded as driver-mutation in SM-AHNMD.

Methods

DNA isolated from peripheral blood (PB) of an SM-CMML patient was investigated with targeted next generation sequencing. Variants were verified by Sanger sequencing and further characterized in the SM part of the bone marrow trephine (BMT), normal tissue, and FACS sorted PB cell subpopulations.

Findings

Low coverage deep-sequencing (mean 10x) on a GS 454 Junior revealed two as yet unreported SNVs (CBFA2T3 and CLTCL1), both germ-line mutations. High coverage (mean 1674x) targeted re-sequencing on an Ion Proton revealed 177 variants in coding regions. Excluding SNPs, the final list comprised 11 variants. Among these, TET2 (p.Thr1027fs, p.Cys1263Ser) and RUNX1 (p.Asn109Ser) were identified in in the peripheral blood and the SM part of BMT, but not in normal tissue. Furthermore, Sanger sequencing of PB cells revealed similar signal intensities for both TET2 mutations in FACS sorted CD34+ precursor cells and CD16+ granulocytes comparable to signals in the SM part of BMT. In contrast, RUNX1 exhibited a double intensity in CD34+ cells compared to the SM part of BMT and a homozygous variant signal in granulocytes. Both TET2 and RUNX1 mutations were not detectable in B- and T-cells.

Conclusion

We present a heterozygous triple-mutation pattern (KIT, TET2, RUNX1) in mast cells (SM disease part) with additional LOH of RUNX1 in granulocytes (CMML disease part). These identified mutations allow a more detailed insight into a multistep pathogenesis which suggests a common tumor progenitor in SM-CMML.

Epidemiology of systemic mastocytosis in Denmark

Mastocytosis is a heterogeneous group of diseases characterized by abnormal proliferation of mast cells. Systemic mastocytosis (SM), in which abnormal mast cells are present in tissues beyond the skin, is divided into seven subcategories with varying degrees of severity and prognosis. Very little is known about the epidemiology of SM and its subcategories. This retrospective cohort study of 548 adults with SM diagnosed 1997-2010 was constructed using linked Danish national health registries. The most common subtype of mastocytosis was indolent SM (including urticaria pigmentosa) (n = 450; 82%), followed by SM with subtype unknown (n = 61; 11%), SM with associated clonal haematological non-mast cell lineage disease (n = 24; 4%), aggressive SM (n = 8; 2%), and mast cell leukaemia (n = 5; 1%). The incidence rate for SM (all subtypes including urticaria pigmentosa) was 0·89 per 100 000 per year. Cumulative incidence was 12·46 per 100 000, and the 14-year limited-duration prevalence as of 1 January, 2011 was 9·59 per 100 000. This nationwide cohort from Denmark is the first population-based epidemiological study of mastocytosis. In this cohort of patients aged 15 years and older, SM was found to be overall relatively rare with notable variation by subtype for patient characteristics, survival and epidemiological measures.

Systemic mastocytosis with associated acute myelogenous leukemia

Systemic mastocytosis (SM) is a condition associated with a clonal neoplastic proliferation of mast cells. Approximately 40% of patients with SM present with an associated clonal hematological non-mast cell lineage disorder. Patients presenting with SM-acute myeloid leukemia (AML) have the worst prognosis. We present a case of a 62-year-old woman who was diagnosed with SM-AML. After initial treatment with a standard regimen of cytosine arabinoside (Ara-C)/idarubicin, her bone marrow showed residual blasts. She was subsequently treated with a second induction regimen of clofarabine and high-dose Ara-C, which resulted in remission of AML, although a residual mast cell infiltrate persisted in her bone marrow. After consolidation therapy with clofarabine/Ara-C, the patient received a stem cell allograft. A follow-up bone marrow showed no residual blasts but persistent mast cells occupying about 5% of the marrow volume.

Systemic mastocytosis accompanied by a non-secretory plasma cell dyscrasia and nephrotic syndrome-level proteinuria in a 76-year-old patient

We report here the interesting case of a 76-year-old man with severe proteinuria who was diagnosed with systemic mastocytosis accompanied by a clonal non-mast-cell lineage haematological disorder (a non-secretory plasma cell dyscrasia). This is a unique report of systemic mastocytosis with a non-secretory plasma cell dyscrasia and nephrotic syndrome. The pathophysiological relevance between these entities along with the probability of occult amyloidosis is discussed.