Chronic myelomonocytic leukemia in younger patients: molecular and cytogenetic predictors of survival and treatment outcome

Chronic myelomonocytic leukemia: 2024 update on diagnosis, risk stratification and management

DISEASE OVERVIEW

Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic stem cell disorder with overlapping features of myelodysplastic syndromes and myeloproliferative neoplasms, characterized by prominent monocytosis and an inherent risk for leukemic transformation (~15%-20% over 3-5 years).

DIAGNOSIS

Newly revised diagnostic criteria include sustained (>3 months) peripheral blood (PB) monocytosis (≥0.5 × 109/L; monocytes ≥10% of leukocyte count), consistent bone marrow (BM) morphology, <20% BM or PB blasts (including promonocytes), and cytogenetic or molecular evidence of clonality. Cytogenetic abnormalities occur in ~30% of patients, while >95% harbor somatic mutations: TET2 (~60%), SRSF2 (~50%), ASXL1 (~40%), RAS pathway (~30%), and others. The presence of ASXL1 and DNMT3A mutations and absence of TET2 mutations negatively impact overall survival (ASXL1WT/TET2MT genotype being favorable).

RISK STRATIFICATION

Several risk models serve similar purposes in identifying high-risk patients that are considered for allogeneic stem cell transplant (ASCT) earlier than later. Risk factors in the Mayo Molecular Model (MMM) include presence of truncating ASXL1 mutations, absolute monocyte count >10 × 109/L, hemoglobin <10 g/dL, platelet count <100 × 109/L, and the presence of circulating immature myeloid cells; the resulting 4-tiered risk categorization includes high (≥3 risk factors), intermediate-2 (2 risk factors), intermediate-1 (1 risk factor), and low (no risk factors); the corresponding median survivals were 16, 31, 59, and 97 months. CMML is also classified as being "myeloproliferative (MP-CMML)" or "myelodysplastic (MD-CMML)," based on the presence or absence of leukocyte count of ≥13 × 109/L.

TREATMENT

ASCT is the only treatment modality that secures cure or long-term survival and is appropriate for MMM high/intermediate-2 risk disease. Drug therapy is currently not disease-modifying and includes hydroxyurea and hypomethylating agents; a recent phase-3 study (DACOTA) comparing hydroxyurea and decitabine, in high-risk MP-CMML, showed similar overall survival at 23.1 versus 18.4 months, respectively, despite response rates being higher for decitabine (56% vs. 31%).

UNIQUE DISEASE ASSOCIATIONS

These include systemic inflammatory autoimmune diseases, leukemia cutis and lysozyme-induced nephropathy; the latter requires close monitoring of renal function during leukocytosis and is a potential indication for cytoreductive therapy.

Role of allogeneic transplantation in chronic myelomonocytic leukemia: an international collaborative analysis

To determine the survival benefit of allogeneic hematopoietic cell transplantation (allo-HCT) in chronic myelomonocytic leukemias (CMML), we assembled a retrospective cohort of CMML patients 18-70 years old diagnosed between 2000 and 2014 from an international CMML dataset (n = 730) and the EBMT registry (n = 384). The prognostic impact of allo-HCT was analyzed through univariable and multivariable time-dependent models and with a multistate model, accounting for age, sex, CMML prognostic scoring system (low or intermediate-1 grouped as lower-risk, intermediate-2 or high as higher-risk) at diagnosis, and AML transformation. In univariable analysis, lower-risk CMMLs had a 5-year overall survival (OS) of 20% with allo-HCT vs 42% without allo-HCT (P < .001). In higher-risk patients, 5-year OS was 27% with allo-HCT vs 15% without allo-HCT (P = .13). With multistate models, performing allo-HCT before AML transformation reduced OS in patients with lower-risk CMML, and a survival benefit was predicted for men with higher-risk CMML. In a multivariable analysis of lower-risk patients, performing allo-HCT before transformation to AML significantly increased the risk of death within 2 years of transplantation (hazard ratio [HR], 3.19; P < .001), with no significant change in long-term survival beyond this time point (HR, 0.98; P = .92). In higher-risk patients, allo-HCT significantly increased the risk of death in the first 2 years after transplant (HR 1.46; P = .01) but not beyond (HR, 0.60; P = .09). Performing allo-HCT before AML transformation decreases life expectancy in lower-risk patients but may be considered in higher-risk patients.

Chronic myelomonocytic leukemia: 2022 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic stem cell disorder with overlapping features of myelodysplastic syndromes and myeloproliferative neoplasms, with an inherent risk for leukemic transformation (~15% over 3-5 years).

DIAGNOSIS

Diagnosis is based on the presence of sustained (>3 months) peripheral blood monocytosis (≥1 × 10⁹ /L; monocytes ≥10%), usually with accompanying bone marrow dysplasia. Clonal cytogenetic abnormalities occur in ~30% of patients, while >90% have somatic gene mutations. Mutations involving TET2 (~60%), SRSF2 (~50%), ASXL1 (~40%), and the oncogenic RAS pathway (~30%) are frequent, while the presence of ASXL1 and DNMT3A mutations and the absence of TET2 mutations negatively impact overall survival.

RISK-STRATIFICATION

Molecularly integrated prognostic models include the Groupe Français des Myélodysplasies, Mayo Molecular Model (MMM), and the CMML specific prognostic model. Risk factors incorporated into the MMM include presence of truncating ASXL1 mutations, absolute monocyte count >10 × 10⁹ /L, hemoglobin <10 g/dL, platelet count <100 × 10⁹ /L, and the presence of circulating immature myeloid cells. The MMM stratifies CMML patients into four groups: high (≥3 risk factors), intermediate-2 (2 risk factors), intermediate-1 (1 risk factor), and low (no risk factors), with median survivals of 16, 31, 59, and 97 months, respectively.

RISK-ADAPTED THERAPY

Hypomethylating agents such as 5-azacitidine and decitabine are commonly used, with overall response rates of ~40%-50% and complete remission rates of ~7%-17%; with no impact on mutational allele burdens. Allogeneic stem cell transplant is the only potentially curative option but is associated with significant morbidity and mortality.

Chronic myelomonocytic leukemia diagnosis and management

Chronic myelomonocytic leukemia (CMML) is a rare, heterogeneous myeloid malignancy classified as a myelodysplastic syndromes/myeloproliferative neoplasm (MDS/MPN) overlap syndrome by the World Health Organization (WHO). Its initial presentation can be incidental or associated with myelodysplastic or myeloproliferative symptoms and up to 20% of patients harbor a concurrent inflammatory or autoimmune condition. Persistent monocytosis is the hallmark of CMML but diagnosis can be challenging. Increased understanding of human monocyte subsets, chromosomal abnormalities, and somatic gene mutations have led to more accurate diagnosis and improved prognostication. A number of risk stratification systems have been developed and validated but using those that incorporate molecular information such as CMML Prognostic Scoring System (CPSS)-Mol, Mayo Molecular, and Groupe Francophone des Myelodysplasies (GFM) are preferred. Symptom-directed approaches forms the basis of CMML management. Outcomes vary substantially depending on risk ranging from observation for a number of years to rapidly progressive disease and acute myeloid leukemia (AML) transformation. Patients who are low risk but with symptoms from cytopenias or proliferative features such as splenomegaly may be treated with hypomethylating agents (HMAs) or cytoreductive therapy, respectively, with the goal of durable symptoms control. Allogeneic hematopoietic cell transplantation should be considered for intermediate to high risk patients. The lack of effective pharmaceutical options has generated interest in novel therapeutics for this disease, and early phase clinical trial results are promising.

Genomic Landscape and Risk Stratification in Chronic Myelomonocytic Leukemia

PURPOSE

The advent of next-generation sequencing has allowed for the annotation of a vast array of recurrent somatic mutations across human malignancies, ushering in a new era of precision oncology. Chronic myelomonocytic leukemia is recognized as a myelodysplastic/myeloproliferative neoplasm and displays heterogenous clinical and genetic features. Herein, we review what is currently understood regarding the genomic landscape of this disease and discuss how somatic mutations have impacted current risk stratification methods.

RECENT FINDINGS

Genomic studies in chronic myelomonocytic leukemia have identified a characteristic spectrum of cytogenetic and molecular abnormalities. Chromosomal abnormalities are detected in ~30% of patients and somatic gene mutations in up to 90% of patients, most commonly in TET2, SRSF2, and ASXL1. While cytogenetic abnormalities have long been known to impact the prognosis of myeloid neoplasms, recent studies have identified that somatic mutations impact prognosis independent of cytogenetic and clinical variables. This is best exemplified by mutations in ASXL1, which have been uniformly associated with inferior survival. These findings have led to the development of three molecularly inspired prognostic models, in an attempt to more accurately prognosticate in the disease. Our understanding of the genomic landscape of chronic myelomonocytic leukemia continues to evolve, with somatic mutations demonstrating an expanding role in diagnosis, risk stratification, and therapeutic decision-making. Given these findings, molecular profiling by next-generation sequencing should be considered standard of care in all patients.

Traipsing Through Muddy Waters: A Critical Review of the Myelodysplastic Syndrome/Myeloproliferative Neoplasm (MDS/MPN) Overlap Syndromes

Myelodysplastic syndrome/Myeloproliferative neoplasms (MDS/MPNs) are molecularly complex, clinically heterogeneous diseases that exhibit proliferative and dysplastic features. Diagnostic criteria use clinical, pathologic, and genomic features to distinguish between disease entities, though considerable clinical and genetic overlap persists. MDS/MPNs are associated with a poor prognosis, save for MDS/MPN with ring sideroblasts and thrombocytosis, which can behave more indolently. The current treatment approach is risk-adapted and symptom-directed and largely extrapolated from experience in MDS or MPN. Gene sequencing has demonstrated frequent mutations involving signaling, epigenetic, and splicing pathways, which present numerous therapeutic opportunities for clinical investigation.

Venetoclax/decitabine for a pediatric patient with chronic myelomonocytic leukemia

Chronic myelomonocytic leukemia (CMML) is a myelodysplastic syndrome (MDS)/myeloproliferative disorder most commonly seen in the elderly. We describe an adolescent with monosomy 7 CMML presenting as central diabetes insipidus (DI), who was treated with venetoclax and decitabine as a bridge to hematopoietic stem cell transplantation (HSCT). Central DI is a rare manifestation of monosomy 7-associated MDS including CMML, itself a rare manifestation of GATA2 deficiency, particularly in children. Venetoclax/decitabine was effective for treatment of CMML as a bridge to HSCT.

Genetic complexity of chronic myelomonocytic leukemia

In recent years CMML has received increased attention as the most commonly observed MDS/MPN overlap syndrome. Renewed interest has occurred in part due to widespread adoption of next-generation sequencing panels that help render the diagnosis in the absence of morphologic dysplasia. Although most CMML patients exhibit somatic mutations in epigenetic modifiers, spliceosome components, transcription factors and signal transduction genes, it is increasingly clear that a small subset harbors an inherited predisposition to CMML and other myeloid neoplasms. More intriguing is the fact that the mutational spectrum observed in CMML is found in other types of myeloid leukemias, begging the question of how similar genetic backgrounds can lead to such divergent clinical phenotypes. In this review we present a contemporary snapshot of the genetic complexity inherent to CMML, explore the relationship between genotype-phenotype and present a stepwise model of CMML pathogenesis and progression.

Chronic Myelomonocytic leukemia: 2020 update on diagnosis, risk stratification and management

DISEASE OVERVIEW

Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic stem cell disorder with overlapping features of myelodysplastic syndromes and myeloproliferative neoplasms, with an inherent risk for leukemic transformation (~15% over 3-5 years).

DIAGNOSIS

Diagnosis is based on the presence of sustained (>3 months) peripheral blood monocytosis (≥1 × 10⁹ /L; monocytes ≥10%), along with bone marrow dysplasia. Clonal cytogenetic abnormalities occur in ~ 30% of patients, while >90% have gene mutations. Mutations involving TET2 (~60%), SRSF2 (~50%), ASXL1 (~40%) and the oncogenic RAS pathway (~30%) are frequent; while the presence of ASXL1 and DNMT3A mutations and the absence of TET2 mutations negatively impact over-all survival.

RISK STRATIFICATION

Molecularly integrated prognostic models include; the Groupe Français des Myélodysplasies (GFM), Mayo Molecular Model (MMM) and the CMML specific prognostic model (CPSS-Mol). Risk factors incorporated into the MMM include presence of nonsense or frameshift ASXL1 mutations, absolute monocyte count>10 × 10⁹ /L, hemoglobin <10 g/dL, platelet count <100 × 10⁹ /L and the presence of circulating immature myeloid cells. The MMM stratifies CMML patients into four groups; high (≥3 risk factors), intermediate-2 (2 risk factors), intermediate-1 (1 risk factor) and low (no risk factors), with median survivals of 16, 31, 59 and 97 months, respectively.

RISK-ADAPTED THERAPY

Hypomethylating agents such as 5-azacitidine and decitabine are commonly used, with overall response rates of ~40%-50% and complete remission rates of ~7%-17%; with no impact on mutational allele burdens. Allogeneic stem cell transplant is the only potentially curative option, but is associated with significant morbidity and mortality.

Diagnosis and Treatment of Chronic Myelomonocytic Leukemias in Adults: Recommendations From the European Hematology Association and the European LeukemiaNet

Chronic myelomonocytic leukemia (CMML) is a disease of the elderly, and by far the most frequent overlap myelodysplastic/myeloproliferative neoplasm in adults. Aside from the chronic monocytosis that remains the cornerstone of its diagnosis, the clinical presentation of CMML includes dysplastic features, cytopenias, excess of blasts, or myeloproliferative features including high white blood cell count or splenomegaly. Prognosis is variable, with several prognostic scoring systems reported in recent years, and treatment is poorly defined, with options ranging from watchful waiting to allogeneic stem cell transplantation, which remains the only curative therapy for CMML. Here, we present on behalf of the European Hematology Association and the European LeukemiaNet, evidence- and consensus-based guidelines, established by an international group of experts, from Europe and the United States, for standardized diagnostic and prognostic procedures and for an appropriate choice of therapeutic interventions in adult patients with CMML.

Chronic myelomonocytic leukemia: 2018 update on diagnosis, risk stratification and management

DISEASE OVERVIEW

Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic stem cell disorder with overlapping features of myelodysplastic syndromes and myeloproliferative neoplasms, with an inherent risk for leukemic transformation (∼15%-20% over 3-5 years).

DIAGNOSIS

Diagnosis is based on the presence of sustained (>3 months) peripheral blood monocytosis (≥1 × 10⁹ /L; monocytes ≥10%), along with bone marrow dysplasia. Clonal cytogenetic abnormalities occur in ∼ 30% of patients, while >90% have gene mutations. Mutations involving TET2 (∼60%), SRSF2 (∼50%), ASXL1 (∼40%) and the oncogenic RAS pathway (∼30%) are frequent; while the presence of ASXL1 and DNMT3A mutations and the absence of TET2 mutations negatively impact over-all survival.

RISK STRATIFICATION

Molecularly integrated prognostic models include; the Groupe Français des Myélodysplasies (GFM), Mayo Molecular Model (MMM), and the CMML specific prognostic model (CPSS-Mol). Risk factors incorporated into the MMM include presence of nonsense or frameshift ASXL1 mutations, absolute monocyte count > 10 × 10⁹ /L, hemoglobin <10 gm/dL, platelet count <100 × 10⁹ /L and the presence of circulating immature myeloid cells. The MMM stratifies CMML patients into 4 groups; high (≥3 risk factors), intermediate-2 (2 risk factors), intermediate-1 (1 risk factor), and low (no risk factors), with median survivals of 16, 31, 59, and 97 months, respectively.

RISK-ADAPTED THERAPY

Hypomethylating agents such as 5-azacitidine and decitabine are commonly used, with overall response rates of ∼30%-40% and complete remission rates of ∼7%-17%; with no impact on mutational allele burdens. Allogeneic stem cell transplant is the only potentially curative option, but is associated with significant morbidity and mortality.

Advances in diagnosis of mastocytosis and hypereosinophilic syndrome☆

Mastocytosis and hypereosinophilic syndrome is very rare neoplastic hematopoietic diseases. Mastocytosis is characterized by expansion and accumulation of clonal tissue mast cells in skin and/or various internal organs, while hypereosinophilic syndrome manifests with an increased number of eosinophils in the peripheral blood and tissue damage. These diseases represent a diagnostic challenge, since they can have overlapping clinical and pathologic features. Recently, great advances in the molecular and immunophenotypic diagnosis of these two entities were achieved, contributing to the new World Health Organization (WHO) classification. The WHO classification of myeloid neoplasms has been revised in 2016 by adding several new entities and refinement of the 2008 WHO classification, in an attempt to incorporate up-to-date clinical, prognostic, morphologic, and molecular genetics data that emerged since 2008. Here we overview the recent advances in disease diagnosis, with a focus on the updated WHO classification, refined diagnostic criteria, and up-to-date molecular findings in these two rare diseases.

CMML: Clinical and molecular aspects

Chronic Myelomonocytic Leukemia is a chronic myeloid neoplasm occurring mostly in the elderly with overlapping features of myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN) characterized by chronic monocytosis. Recent progresses in the molecular and cellular pathogenesis of CMML have stirred a renewed interest in this clinically heterogeneous disorder. Here, we review the recent progresses in the biology of CMML and how it affects its current and future clinical management.

TET2 mutations were predictive of inferior prognosis in the presence of ASXL1 mutations in patients with chronic myelomonocytic leukemia

BACKGROUND

Somatic mutations involving epigenetic regulators, histone modification and chromatin regulation, splicing components, transcription factors and signaling regulator genes are common in chronic myelomonocytic leukemia (CMML) patients. It has been consensus that ASXL1 mutations have adversely impact on overall survival (OS), while the effect of TET2 mutations remains controversial and undefined.

METHODS

ASXL1 and TET2 mutations were analyzed in 141 patients with CMML using Sanger sequencing, with the aim to identify the interplay of ASXL1 and TET2 mutations in the prognosis of CMML.

RESULTS

Sixty-five (46.1%) of the CMML patients harbored ASXL1 mutations (frameshift and nonsense), and 46 (32.6%) had TET2 mutations (frame shift, nonsense and missense). In a separate multivariable analysis that included the Mayo Prognostic Model as a single variable along with ASXL1wt/TET2wt, the respective hazard ratios of ASXL1mut/TET2mut, ASXL1mut/TET2wt and ASXL1wt/TET2mut were 4.7 (95% CI, 2.2-10.3; P<0.001), 2.2 (95% CI, 1.1-4.2; P=0.025) and 1.3 (95% CI, 0.6-2.5; P=0.521).

CONCLUSIONS

Our study showed that ASXL1 mutations predict inferior OS, and additional TET2 mutations were associated with poor survival in the presence of ASXL1 mutations of CMML patients.

Chronic myelomonocytic leukemia: 2016 update on diagnosis, risk stratification, and management

Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic stem cell disorder characterized by overlapping features of myelodysplastic syndromes and myeloproliferative neoplasms. Diagnosis is based on the presence of persistent (>3 months) peripheral blood monocytosis (>1 × 10(9) /L), along with bone marrow dysplasia. Clonal cytogenetic abnormalities occur in ∼20-30% of patients, while >90% have gene mutations. Mutations involving TET2 (∼60%), SRSF2 (∼50%), ASXL1 (∼40%), and RAS (∼30%) are frequent; with only ASXL1 mutations negatively impacting overall survival. Two molecularly integrated, CMML-specific prognostic models include; the Groupe Français des Myélodysplasies (GFM) and the Molecular Mayo Model (MMM). The GFM model segregates patients into 3 groups based on: age >65 years, WBC >15 × 10(9) /L, anemia, platelets <100 × 10(9) /L, and ASXL1 mutation status, with respective median survivals of 56 (low), 27.4 (intermediate), and 9.2 (high) months. The MMM is based on ASXL1 mutational status, absolute monocyte count >10 × 10(9) /L, hemoglobin <10 g/dL, platelets <100 × 109/L and circulating immature myeloid cells. This model stratifies patients into four groups; high (≥3 risk factors), intermediate-2 (2 risk factors), intermediate-1 (1 risk factor) and low (no risk factors), with median survivals of 16, 31, 59, and 97 months, respectively. Hypomethylating agents such as 5-azacitidine and decitabine are commonly used, with overall response rates of ∼30-40% and complete remission rates of ∼7-17%. Allogeneic stem cell transplant is the only potentially curative option, but is associated with significant morbidity and mortality. Individualized therapy, including epigenetic modifiers and small molecule inhibitors, are exciting prospects. Am. J. Hematol. 91:632-642, 2016. © 2016 Wiley Periodicals, Inc.

Cytogenetic and molecular abnormalities in chronic myelomonocytic leukemia

Chronic myelomonocytic leukemia (CMML) is a clonal stem cell disorder associated with peripheral blood monocytosis and an inherent tendency to transform to acute myeloid leukemia. CMML has overlapping features of myelodysplastic syndromes and myeloproliferative neoplasms. Clonal cytogenetic changes are seen in ~30%, whereas gene mutations are seen in >90% of patients. Common cytogenetic abnormalities include; trisomy 8, -Y, -7/del(7q), trisomy 21 and del(20q), with the Mayo-French risk stratification effectively risk stratifying patients based on cytogenetic abnormalities. Gene mutations frequently involve epigenetic regulators (TET2 ~60%), modulators of chromatin (ASXL1 ~40%), spliceosome components (SRSF2 ~50%), transcription factors (RUNX1 ~15%) and signal pathways (RAS ~30%, CBL ~15%). Of these, thus far, only nonsense and frameshift ASXL1 mutations have been shown to negatively impact overall survival. This has resulted in the development of contemporary, molecularly integrated (inclusive of ASXL1 mutations) CMML prognostic models, including Molecular Mayo Model and the Groupe Français des Myélodysplasies model. Better understanding of the prevalent genetic and epigenetic dysregulation has resulted in emerging targeted treatment options for some patients. The development of an integrated (cytogenetic and molecular) prognostic model along with CMML-specific response assessment criteria are much needed future goals.

Chronic Myelomonocytic Leukemia: Focus on Clinical Practice

Chronic myelomonocytic leukemia (CMML) is a clonal stem cell disorder with features that overlap those of myelodysplastic syndromes (MDSs) and myeloproliferative neoplasms (MPNs). Chronic myelomonocytic leukemia often results in peripheral blood monocytosis and has an inherent tendency to transform to acute myeloid leukemia. Clonal cytogenetic changes are seen in approximately 30% of patients, and molecular abnormalities are seen in more than 90%. Gene mutations involving TET2 (∼60%), SRSF2 (∼50%), ASXL1 (∼40%), and RAS (∼30%) are frequent, with nonsense and frameshift ASXL1 mutations being the only mutations identified thus far to have an independent negative prognostic effect on overall survival. Contemporary molecularly integrated prognostic models (inclusive of ASXL1 mutations) include the Molecular Mayo Model and the Groupe Français des Myélodysplasies model. Given the lack of formal treatment and response criteria, management of CMML is often extrapolated from MDS and MPN, with allogeneic stem cell transplant being the only curative option. Hydroxyurea and other cytoreductive agents have been used to control MPN-like features, while epigenetic modifiers such as hypomethylating agents have been used for MDS-like features. Given the relatively poor response to these agents and the inherent risks associated with hematopoietic stem cell transplant, newer drugs exploiting molecular and epigenetic abnormalities in CMML are being developed. The creation of CMML-specific response criteria is a much needed step in order to improve clinical outcomes.

Prognostic interaction between ASXL1 and TET2 mutations in chronic myelomonocytic leukemia

Mutations involving epigenetic regulators (TET2~60% and ASXL1~40%) and splicing components (SRSF2~50%) are frequent in chronic myelomonocytic leukemia (CMML). On a 27-gene targeted capture panel performed on 175 CMML patients (66% males, median age 70 years), common mutations included: TET2 46%, ASXL1 47%, SRSF2 45% and SETBP1 19%. A total of 172 (98%) patients had at least one mutation, 21 (12%) had 2, 24 (14%) had 3 and 30 (17%) had >3 mutations. In a univariate analysis, the presence of ASXL1 mutations (P=0.02) and the absence of TET2 mutations (P=0.03), adversely impacted survival; while the number of concurrent mutations had no impact (P=0.3). In a multivariable analysis that included hemoglobin, platelet count, absolute monocyte count and circulating immature myeloid cells (Mayo model), the presence of ASXL1 mutations (P=0.01) and absence of TET2 mutations (P=0.003) retained prognostic significance. Patients were stratified into four categories: ASXL1wt/TET2wt (n=56), ASXL1mut/TET2wt (n=31), ASXL1mut/TET2mut (n=50) and ASXL1wt/TET2mut (n=38). Survival data demonstrated a significant difference in favor of ASXL1wt/TET2mut (38 months; P=0.016), compared with those with ASXL1wt/TET2wt (19 months), ASXL1mut/TET2wt (21 months) and ASXL1mut/TET2mut (16 months) (P=0.3). We confirm the negative prognostic impact imparted by ASXL1 mutations and suggest a favorable impact from TET2 mutations in the absence of ASXL1 mutations.

Additional mutations in SRSF2, ASXL1 and/or RUNX1 identify a high-risk group of patients with KIT D816V(+) advanced systemic mastocytosis

Most patients with KIT D816V(+) advanced systemic mastocytosis (SM) are characterized by somatic mutations in additional genes. We sought to clarify the prognostic impact of such mutations. Genotype and clinical characteristics of 70 multi-mutated KIT D816V(+) advanced SM patients were included in univariate and multivariate analyses. The most frequently identified mutated genes were TET2 (n=33 of 70 patients), SRSF2 (n=30), ASXL1 (n=20), RUNX1 (n=16) and JAK2 (n=11). In univariate analysis, overall survival (OS) was adversely influenced by mutations in SRSF2 (P<0.0001), ASXL1 (P=0.002) and RUNX1 (P=0.03), but was not influenced by mutations in TET2 or JAK2. In multivariate analysis, SRSF2 and ASXL1 remained the most predictive adverse indicators concerning OS. Furthermore, we found that inferior OS and adverse clinical characteristics were significantly influenced by the number of mutated genes in the SRSF2/ASXL1/RUNX1 (S/A/R) panel (P<0.0001). In conclusion, the presence and number of mutated genes within the S/A/R panel are adversely associated with advanced disease and poor survival in KIT D816V(+) SM. On the basis of these findings, inclusion of molecular markers should be considered in upcoming prognostic scoring systems for patients with SM.