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.

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.

Nintedanib targets KIT D816V neoplastic cells derived from induced pluripotent stem cells of systemic mastocytosis.

The KIT D816V mutation is found in >80% of patients with systemic mastocytosis (SM) and is key to neoplastic mast cell (MC) expansion and accumulation in affected organs. Therefore, KIT D816V represents a prime therapeutic target for SM. Here, we generated a panel of patient-specific KIT D816V induced pluripotent stem cells (iPSCs) from patients with aggressive SM and mast cell leukemia to develop a patient-specific SM disease model for mechanistic and drug-discovery studies. KIT D816V iPSCs differentiated into neoplastic hematopoietic progenitor cells and MCs with patient-specific phenotypic features, thereby reflecting the heterogeneity of the disease. CRISPR/Cas9n-engineered KIT D816V human embryonic stem cells (ESCs), when differentiated into hematopoietic cells, recapitulated the phenotype observed for KIT D816V iPSC hematopoiesis. KIT D816V causes constitutive activation of the KIT tyrosine kinase receptor, and we exploited our iPSCs and ESCs to investigate new tyrosine kinase inhibitors targeting KIT D816V. Our study identified nintedanib, a US Food and Drug Administration-approved angiokinase inhibitor that targets vascular endothelial growth factor receptor, platelet-derived growth factor receptor, and fibroblast growth factor receptor, as a novel KIT D816V inhibitor. Nintedanib selectively reduced the viability of iPSC-derived KIT D816V hematopoietic progenitor cells and MCs in the nanomolar range. Nintedanib was also active on primary samples of KIT D816V SM patients. Molecular docking studies show that nintedanib binds to the adenosine triphosphate binding pocket of inactive KIT D816V. Our results suggest nintedanib as a new drug candidate for KIT D816V-targeted therapy of advanced SM.

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 (HMAs) 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- 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.

Definition of factors associated with negative antibody response after COVID-19 vaccination in patients with hematological diseases.

COVID-19 in patients with hematological diseases is associated with a high mortality. Moreover, preventive vaccination demonstrated reduced efficacy and the knowledge on influencing factors is limited. In this single-center study, antibody levels of the SARS-CoV-2 spike protein were measured ≥ 2 weeks after 2nd COVID-19 vaccination with a concentration ≥ 0.8 U/mL considered positive. Between July and October 2021, in a total of 373 patients (median age 64 years, 44% women) with myeloid neoplasms (n = 214, 57%), lymphoid neoplasms (n = 124, n = 33%), and other diseases (n = 35, 10%), vaccination was performed with BNT162b2 (BioNTech), mRNA-1273 (Moderna), ChADOx1 (AstraZeneca), or a combination. A total of 229 patients (61%) were on active therapy within 3 months prior vaccination and 144 patients (39%) were previously treated or treatment naïve. Vaccination-related antibody response was negative in 56/373 patients (15%): in 39/124 patients with lymphoid neoplasms, 13/214 with myeloid neoplasms, and 4/35 with other diseases. Active treatment per se was not correlated with negative response. However, rituximab and BTK inhibitor treatment were correlated significantly with a negative vaccination response, whereas younger age and chronic myeloid leukemia (CML) disease were associated with positive response. In addition, 5 of 6 patients with myeloproliferative neoplasm (MPN) and negative vaccination response were on active treatment with ruxolitinib. In conclusion, a remarkable percentage of patients with hematological diseases had no response after 2nd COVID-19 vaccination. Multivariable analysis revealed important factors associated with response to vaccination. The results may serve as a guide for better protection and surveillance in this vulnerable patient cohort.

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.

Low risk of contrast media-induced hypersensitivity reactions in all subtypes of systemic mastocytosis.

BACKGROUND: Patients with systemic mastocytosis (SM) are at increased risk of hypersensitivity reactions (HRs). Although Hymenoptera venoms are the predominant triggers, cases of contrast media-induced HR (CMIHR) have also been reported and prophylactic premedication is often performed. However, data from larger series are limited and differences between indolent and advanced SM have not yet been investigated. OBJECTIVE: To determine the incidence and severity of CMIHR in all subtypes of SM. METHODS: We analyzed 162 adult patients with SM (indolent systemic mastocytosis [ISM], n = 65; advanced systemic mastocytosis [advSM], n = 97). First, the cumulative incidence of CMIHR was retrospectively assessed in the patient's history. Second, at our institution, patients underwent 332 contrast media (CM)-enhanced imaging including 80 computed tomography (CT) scans with iodine-based contrast agent and 252 magnetic resonance imaging (MRI) with a gadolinium-based contrast agent, and tolerance was assessed. RESULTS: Previous CMIHRs to CT (vomiting, n = 1, erythema, n = 1, cardiovascular shock, n = 1), and MRI (dyspnea, n = 1, cardiovascular shock, n = 1) had been reported by 4 out of 162 (2.5%) patients (ISM, n = 3; advSM, n = 1). In contrast, during or after 332 CM-enhanced CT or MRI examinations at our institution, no CMIHRs were reported. Premedication was solely given to 3 patients before CT scans, including 1 with previous CMIHR, who tolerated the imaging well. CONCLUSION: We conclude that: (1) there is a substantial discrepancy between the perception and prevalence of HRs to CM in SM; (2) reactions are scarce in ISM and even rarer in advSM; and (3) in SM patients without previous history of CM hypersensitivity, prophylactic premedication before CM-enhanced CT or MRI is dispensable.

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 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 (JAK2pos. /KITpos. ) 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 JAK2pos. /KITpos. 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.

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.

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.

Adverse Prognostic Impact of the KIT D816V Transcriptional Activity in Advanced Systemic Mastocytosis.

In systemic mastocytosis (SM), qualitative and serial quantitative assessment of the KIT D816V mutation is of diagnostic and prognostic relevance. We investigated peripheral blood and bone marrow samples of 161 patients (indolent SM (ISM), n = 40; advanced SM, AdvSM, n = 121) at referral and during follow-up for the KIT D816V variant allele frequency (VAF) at the DNA-level and the KIT D816V expressed allele burden (EAB) at the RNA-level. A round robin test with four participating laboratories revealed an excellent correlation (r > 0.99, R2 > 0.98) between three different DNA-assays. VAF and EAB strongly correlated in ISM (r = 0.91, coefficient of determination, R2 = 0.84) but only to a lesser extent in AdvSM (r = 0.71; R2 = 0.5). However, as compared to an EAB/VAF ratio ≤2 (cohort A, 77/121 patients, 64%) receiver operating characteristic (ROC) analysis identified an EAB/VAF ratio of >2 (cohort B, 44/121 patients, 36%) as predictive for an advanced phenotype and a significantly inferior median survival (3.3 vs. 11.7 years; p = 0.005). In terms of overall survival, Cox-regression analysis was only significant for the EAB/VAF ratio >2 (p = 0.006) but not for VAF or EAB individually. This study demonstrates for the first time that the transcriptional activity of KIT D816V may play an important role in the pathophysiology of SM.

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.

LCP1 triggers mTORC2/AKT activity and is pharmacologically targeted by enzastaurin in hypereosinophilia.

Hypereosinophilia (HE) is caused by a variety of disorders, ranging from parasite infections to autoimmune diseases and cancer. Only a small proportion of HE cases are clonal malignancies, and one of these, the group of eosinophilia-associated tyrosine kinase fusion-driven neoplasms, is sensitive to tyrosine kinase inhibitors, while most subtypes lack specific treatment. Eosinophil functions are highly dependent on actin polymerization, promoting priming, shape change, and infiltration of inflamed tissues. Therefore, we investigated the role of the actin-binding protein lymphocyte cytosolic protein 1 (LCP1) in malignant and nonmalignant eosinophil differentiation. We use the protein kinase C-ß (PKCß) selective inhibitor enzastaurin (Enza) to dephosphorylate and inactivate LCP1 in FIP1L1-platelet-derived growth factor receptor α (PDGFRA)-positive Eol-1 cells, and this was associated with reduced proliferation, metabolic activity, and colony formation as well as enhanced apoptosis and impaired migration. While Enza did not alter FIP1L1-PDGFRA-induced signal transducer and activator of transcription 3 (STAT3), STAT5, and ERK1/2 phosphorylation, it inhibited STAT1Tyr701 and AKTSer473 (but not AKTThr308 ) phosphorylation, and short hairpin RNA knockdown experiments confirmed that this process was mediated by LCP1 and associated mammalian target of rapamycin complex 2 (mTORC2) activity loss. Homeobox protein HoxB8 immortalized murine bone marrow cells showed impaired eosinophilic differentiation upon Enza treatment or LCP1 knockdown. Furthermore, Enza treatment of primary HE samples reduced eosinophil differentiation and survival. In conclusion, our data show that HE involves active LCP1, which interacts with mTOR and triggers mTORC2 activity, and that the PKCß inhibitor Enza as well as targeting of LCP1 may provide a novel treatment approach to hypereosinophilic disorders.

CD44 is a RAS/STAT5-regulated invasion receptor that triggers disease expansion in advanced mastocytosis.

The Hermes receptor CD44 is a multifunctional adhesion molecule that plays an essential role in the homing and invasion of neoplastic stem cells in various myeloid malignancies. Although mast cells (MCs) reportedly express CD44, little is known about the regulation and function of this receptor in neoplastic cells in systemic mastocytosis (SM). We found that clonal CD34+/CD38- stem cells, CD34+/CD38+ progenitor cells, and CD117++/CD34- MCs invariably express CD44 in patients with indolent SM (ISM), SM with an associated hematologic neoplasm, aggressive SM, and MC leukemia (MCL). In addition, all human MCL-like cell lines examined (HMC-1, ROSA, and MCPV-1) displayed cytoplasmic and cell-surface CD44. We also found that expression of CD44 in neoplastic MCs depends on RAS-MEK and STAT5 signaling and increases with the aggressiveness of SM. Correspondingly, higher levels of soluble CD44 were measured in the sera of patients with advanced SM compared with ISM or cutaneous mastocytosis and were found to correlate with overall and progression-free survival. To investigate the functional role of CD44, a xenotransplantation model was employed using severe combined immunodeficient (SCID) mice, HMC-1.2 cells, and a short hairpin RNA (shRNA) against CD44. In this model, the shRNA-mediated knockdown of CD44 resulted in reduced MC expansion and tumor formation and prolonged survival in SCID mice compared with HMC-1.2 cells transduced with control shRNA. Together, our data show that CD44 is a RAS-MEK/STAT5-driven MC invasion receptor that correlates with the aggressiveness of SM. Whether CD44 can serve as therapeutic target in advanced SM remains to be determined in forthcoming studies.

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.

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.

Response and progression on midostaurin in advanced systemic mastocytosis: KIT D816V and other molecular markers.

In advanced systemic mastocytosis (advSM), disease evolution is often triggered by KIT mutations (D816V in >80% of cases) and by additional mutations (eg, in SRSF2, ASXL1, and/or RUNX1 [S/A/Rpos in >60% of cases]). In a recently reported phase 2 study, midostaurin, a multikinase/KIT inhibitor, demonstrated an overall response rate (ORR) of 60% in advSM but biomarkers predictive of response are lacking. We evaluated the impact of molecular markers at baseline and during follow-up in 38 midostaurin-treated advSM patients. The median overall survival (OS) was 30 months (95% confidence interval, 6-54) from start of midostaurin. ORR and OS were significantly different between S/A/Rneg (n = 12) and S/A/Rpos (n = 23) patients (ORR: 75% vs 39%, P = .04; OS: P = .01, HR 4.5 [1.3-16.2]). Depending on the relative reduction of the KIT D816V expressed allele burden (EAB) at month 6, patients were classified as KIT responders (≥25%, n = 17) or KIT nonresponders (<25%, n = 11). In univariate analyses at month 6, reduction of KIT D816V EAB ≥25%, tryptase ≥50%, and alkaline phosphatase ≥50% were significantly associated with improved OS. In multivariate analysis, only KIT D816V EAB reduction ≥25% remained an independent on-treatment marker for improved OS (P = .004, HR 6.8 [1.8-25.3]). Serial next-generation sequencing analysis of 28 genes in 16 patients revealed acquisition of additional mutations or increasing variant allele frequency in K/NRAS, RUNX1, IDH2, or NPM1 associated with progression in 7 patients. In midostaurin-treated advSM patients, the complexity and dynamics of mutational profiles significantly affect response, progression, and prognosis.

Magnetic resonance imaging reveals distinct bone marrow patterns in indolent and advanced systemic mastocytosis.

Systemic mastocytosis (SM) is broadly subcategorized according to mast cell (MC) burden and organ involvement into indolent (ISM), smoldering (SSM), and advanced SM (AdvSM). However, the pattern and extent of bone involvement remains controversial. In this institutional review board (IRB)-approved study, 115 patients with different forms of SM (ISM (n = 37, 32%), SSM (n = 9, 8%), and AdvSM (n = 69, 60%)) underwent a whole-body magnetic resonance imaging including sagittal and coronal T1 and turbo inversion recovery magnitude (TIRM) sequences of the spine. The evaluation included the pattern and extent of pathologic bone marrow (BM) signals in the spine and extremities, osteolytic lesions, and vertebral fractures. A pathologic BM pattern was observed in 4/37 (11%), 8/9 (89%), and 66/69 (96%); affection of the appendicular skeleton in 3/37 (8%), 8/9 (89%), and 67/69 (97%); and vertebral fractures in 7/37 (19%), 0/9, and 13/69 (19%) patients with ISM, SSM, and AdvSM, respectively. In AdvSM, pathologic BM pattern included activated (62%), diffuse sclerotic (25%), and small-spotted BM (9%), respectively. Only activated/sclerotic BM was associated with significantly higher MC burden, organ damage, and inferior median survival (2.9 years, p = 0.04). Vertebral fractures resembled classical multi-segmental osteoporotic fractures in ISM but not in AdvSM in which they were only found in activated/sclerotic BM. Only one patient with AdvSM had a focal osteolytic lesion in the femur. Activated/sclerotic BM changes of the spine and affection of the appendicular skeleton are indicative for SSM or AdvSM. Osteolytic lesions, which are very rare, and osteoporotic fractures are ineligible for the diagnosis of AdvSM.

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.