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.

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

In patients with chronic myelomonocytic leukemia (CMML), age>65 years is an adverse prognostic factor. Our objective in the current study was to examine risk factors for survival and treatment outcome in 261 'young' adults with CMML, as defined by age ⩽65 years. In multivariable analysis, lower HB (P=0.01), higher circulating blast % (P=0.002), ASXL1 (P=0.0007) and SRSF2 mutations (P=0.008) and Mayo-French cytogenetic stratification (P=0.04) negatively impacted survival. Similarly, leukemia-free survival was independently affected by higher circulating blast % (P<0.0001), higher bone marrow blast % (P=0.0007) and the presence of circulating immature myeloid cells (P=0.0002). Seventy-five (29%) patients received hypomethylating agents (HMA), with the median number of cycles being 5, and the median duration of therapy being 5 months. The over-all response rate was 40% for azacitidine and 30% for decitabine. Fifty-three (24%) patients underwent an allogeneic hematopoietic stem cell transplant (AHSCT), with a response rate of 56% and a non-relapse mortality of 19%. Survival in young adults with CMML, although higher than in older patients, is poor and even worse in the presence of ASXL1 and SRSF2 mutations. Treatment outcome was more impressive with AHSCT than with HMA and neither was influenced by ASXL1/SRSF2 mutations or karyotype.

Novel recurrent mutations in ethanolamine kinase 1 (ETNK1) gene in systemic mastocytosis with eosinophilia and chronic myelomonocytic leukemia.

Although KITD816V occurs universally in adult systemic mastocytosis (SM), the clinical heterogeneity of SM suggests presence of additional phenotype-patterning mutations. Because up to 25% of SM patients have KITD816V-positive eosinophilia, we undertook whole-exome sequencing in a patient with aggressive SM with eosinophilia to identify novel genetic alterations. We conducted sequencing of purified eosinophils (clone/tumor sample), with T-lymphocytes as the matched control/non-tumor sample. In addition to KITD816V, we identified a somatic missense mutation in ethanolamine kinase 1 (ETNK1N244S) that was not present in 50 healthy controls. Targeted resequencing of 290 patients showed ETNK1 mutations to be distributed as follows: (i) SM (n=82; 6% mutated); (ii) chronic myelomonocytic leukemia (CMML; n=29; 14% mutated); (iii) idiopathic hypereosinophilia (n=137; <1% mutated); (iv) primary myelofibrosis (n=32; 0% mutated); and (v) others (n=10; 0% mutated). Of the 82 SM cases, 25 had significant eosinophilia; of these 20% carried ETNK1 mutations. The ten mutations (N244S=6, N244T=1, N244K=1, G245A=2) targeted two contiguous amino acids in the ETNK1 kinase domain, and are predicted to be functionally disruptive. In summary, we identified novel somatic missense ETNK1 mutations that were most frequent in SM with eosinophilia and CMML; this suggests a potential pathogenetic role for dysregulated cytidine diphosphate-ethanolamine pathway metabolites in these diseases.

Calreticulin mutations and long-term survival in essential thrombocythemia.

The impact of calreticulin (CALR) mutations on long-term survival in essential thrombocythemia (ET) was examined in 299 patients whose diagnosis predated 2006. Mutational frequencies were 53% for Janus kinase 2 (JAK2), 32% for CALR and 3% for MPL; the remaining 12% were 'triple-negative'. We confirmed the association of mutant CALR (vs JAK2V617F) with younger age (P=0.002), male sex (P=0.01), higher platelet count (0.0004), lower hemoglobin (P<0.0001), lower leukocyte count (0.02) and lower incidence of recurrent thrombosis (0.04). Triple-negative patients were also younger than their JAK2-mutated counterparts (P=0.003) and displayed lower hemoglobin (P=0.003), lower leukocyte count (<0.0001) and lower thrombotic events (P=0.02). Median follow-up time was 12.7 years and 47% of the patients were followed until death. Survival was the longest for triple-negative and shortest for MPL-mutated patients. Median survival was 19 years for JAK2 and 20 years for CALR-mutated cases (P=0.32); the corresponding figures for patients of age ⩽65 years were 26 and 32 years (P=0.56). The two mutational categories were also similar for leukemic (P=0.28) and fibrotic (P=0.28) progression rates. The current study is uniquely characterized by its very long follow-up period and provides accurate estimates of long-term survival in ET and complements current information on mutation-specific phenotype and prognosis.

ASXL1 and SETBP1 mutations and their prognostic contribution in chronic myelomonocytic leukemia: a two-center study of 466 patients.

In a cohort of 466 patients, we sought to clarify the prognostic relevance of ASXL1 and SETBP1 mutations, among others, in World Health Organization-defined chronic myelomonocytic leukemia (CMML) and its added value to the Mayo prognostic model. In univariate analysis, survival was adversely affected by ASXL1 (nonsense and frameshift) but not SETBP1 mutations. In multivariable analysis, ASXL1 mutations, absolute monocyte count >10 × 10(9)/l, hemoglobin <10 g/dl, platelets <100 × 10(9)/l and circulating immature myeloid cells were independently predictive of shortened survival: hazard ratio (95% confidence interval (CI)) values were 1.5 (1.1-2.0), 2.2 (1.6-3.1), 2.0 (1.6-2.6), 1.5 (1.2-1.9) and 2.0 (1.4-2.7), respectively. A regression coefficient-based prognostic model based on these five risk factors delineated high (≥3 risk factors; HR 6.2, 95% CI 3.7-10.4) intermediate-2 (2 risk factors; HR 3.4, 95% CI 2.0-5.6) intermediate-1 (one risk factor; HR 1.9, 95% CI 1.1-3.3) and low (no risk factors) risk categories with median survivals of 16, 31, 59 and 97 months, respectively. Neither ASXL1 nor SETBP1 mutations predicted leukemic transformation. The current study confirms the independent prognostic value of nonsense/frameshift ASXL1 mutations in CMML and signifies its added value to the Mayo prognostic model, as had been shown previously in the French consortium model.

The number of prognostically detrimental mutations and prognosis in primary myelofibrosis: an international study of 797 patients.

We recently defined a high-molecular risk category (HMR) in primary myelofibrosis (PMF), based on the presence of at least one of the five 'prognostically detrimental' mutated genes (ASXL1, EZH2, SRSF2 and IDH1/2). Herein, we evaluate the additional prognostic value of the 'number' of mutated genes. A total of 797 patients were recruited from Europe (n=537) and the Mayo Clinic (n=260). In the European cohort, 167 (31%) patients were HMR: 127 (23.6%) had one and 40 (7.4%) had two or more mutated genes. The presence of two or more mutations predicted the worst survival: median 2.6 years (hazard ratio (HR) 3.8, 95% confidence interval (CI) 2.6-5.7) vs. 7.0 years (HR 1.9, 95% CI 1.4-2.6) for one mutation vs 12.3 years for no mutations. The results were validated in the Mayo cohort and prognostic significance in both cohorts was independent of International Prognostic Scoring System (IPSS; HR 2.4, 95% CI 1.6-3.6) and dynamic IPSS (DIPSS)-plus (HR 1.9, 95% CI 1.2-3.1), respectively. Two or more mutations were also associated with shortened leukemia-free survival (HR 6.2, 95% CI 3.5-10.7), also Mayo validated. Calreticulin mutations favorably affected survival, independently of both number of mutations and IPSS/DIPSS-plus. We conclude that the 'number' of prognostically detrimental mutations provides added value in the combined molecular and clinical prognostication of PMF.

CALR and ASXL1 mutations-based molecular prognostication in primary myelofibrosis: an international study of 570 patients.

Current prognostication in primary myelofibrosis (PMF) is based on the dynamic international prognostic scoring system (DIPSS)-plus, which employs clinical and cytogenetic variables. We recently reported DIPSS-plus independent prognostic significance for calreticulin (CALR) (favorable) and ASXL1 (unfavorable) mutations. In the current study, 570 PMF patients were recruited for derivation (n=277) and validation (n=293) of a molecular prognostic model based on these two mutations. Survival was the longest in CALR(+)ASXL1(-) (median 10.4 years) and shortest in CALR(-)ASXL1(+) patients (median, 2.3 years; hazard ratio (HR), 5.9; 95% confidence interval (CI), 3.5-10.0). CALR(+)ASXL1(+) and CALR(-)ASXL1(-) patients had similar survival and were grouped together in an intermediate-risk category (median survival, 5.8 years; HR, 2.5; 95% CI, 1.5-4.0). The CALR/ASXL1 mutations-based prognostic model was DIPSS-plus independent (P<0.0001) and effective in identifying low-/intermediate-1-risk patients with shorter (median, 4 years) or longer (median 20 years) survival and high-/intermediate-2-risk patients with shorter (median, 2.3 years) survival. Multivariable analysis distinguished CALR(-)ASXL1(+) mutational status as the most significant risk factor for survival: HR 3.7 vs 2.8 for age >65 years vs 2.7 for unfavorable karyotype. These observations signify immediate clinical relevance and warrant i) CALR and ASXL1 mutation determination in all patients with PMF and ii) molecular revision of DIPSS-plus.

CALR vs JAK2 vs MPL-mutated or triple-negative myelofibrosis: clinical, cytogenetic and molecular comparisons.

Calreticulin (CALR) mutations were recently described in JAK2 and MPL unmutated primary myelofibrosis (PMF) and essential thrombocythemia. In the current study, we compared the clinical, cytogenetic and molecular features of patients with PMF with or without CALR, JAK2 or MPL mutations. Among 254 study patients, 147 (58%) harbored JAK2, 63 (25%) CALR and 21 (8.3%) MPL mutations; 22 (8.7%) patients were negative for all three mutations, whereas one patient expressed both JAK2 and CALR mutations. Study patients were also screened for ASXL1 (31%), EZH2 (6%), IDH (4%), SRSF2 (12%), SF3B1 (7%) and U2AF1 (16%) mutations. In univariate analysis, CALR mutations were associated with younger age (P<0.0001), higher platelet count (P<0.0001) and lower DIPSS-plus score (P=0.02). CALR-mutated patients were also less likely to be anemic, require transfusions or display leukocytosis. Spliceosome mutations were infrequent (P=0.0001) in CALR-mutated patients, but no other molecular or cytogenetic associations were evident. In multivariable analysis, CALR mutations had a favorable impact on survival that was independent of both DIPSS-plus risk and ASXL1 mutation status (P=0.001; HR 3.4 for triple-negative and 2.2 for JAK2-mutated). Triple-negative patients also displayed inferior LFS (P=0.003). The current study identifies 'CALR(-)ASXL1(+)' and 'triple-negative' as high-risk molecular signatures in PMF.