Characteristics Of Patients With Clinical And Molecular Biology Of Essential Thrombocythemia

Background:Essential thrombocythemia (ET) is the most common type of Philadelphia chromosome negative myeloproliferative neoplasms characterized by increased risk of vascular events (thrombosis and hemorrhage). Traditionally, advanced age≥60and history of thrombosis are regarded as predictive risk factors for thrombosis. Recently, a new International Prognostic Score of thrombosis for ET (IPSET-thrombosis) was proposed to predict thrombotic events.Objectives:To analyze clinical and biological characteristics of ET, and to evaluate the prognostic value and clinical implication of the IPSET-thrombosis model in a large cohort of Chinese ET patients.Methods:We retrospectively evaluated the characteristics and risk factors for thrombosis in Chinese patients diagnosed with ET in our hospital from1982to2012. Their clinical data were carefully reassessed, and all of them met the2008WHO criteria. Cox proportional hazards regression was employed to carry out univariate survival analysis, and factors that were significant were forced to multivariate survival analysis. The C-index was calculated based on Receiver Operating Characteristic curve using prognostic index. Thrombosis-free survival was estimated by Kaplan-Meier method, and log-rank test was used to compare thrombosis-free survival data.Results:A total of970ET patients were enrolled. The median follow-up was49months (range,0-360). Chinese ET patients had similar clinical characteristics as Caucasian patients. JAK2V617F mutation was investigated in746patients among whom380(50.9%) were positive. During follow-up,99(10.2%) patients experienced at least one major thrombotic event. The5-,10-, and15-yr cumulative rates of thrombotic events were9.0%,22.0%, and35.0%, respectively. Similar to the IPSET-thrombosis study, our multivariate analysis revealed age>60(HR=1.949), previous thrombosis (HR=2.484), JAK2V617F mutation (HR=1.719), and cardiovascular risk factors (HR=1.877) as independent risk factors for thrombosis. We confirmed that the above risk factors in IPSET-thrombosis, when compared with traditional risk factors (e.g., age≥60and previous thrombotic events), were more predictive of thrombotic events (C-index0.714vs.0.647). Classification by IPSET-thrombosis risk groups revealed different cumulative thrombosis-free survival (P<0.001). For treatment, patients in the intermediate-and high-risk group derived clinical benefit from cytoreductive agents (P<0.05), but those in the low-risk group did not (P=0.446). The lower risk of thrombosis on cytoreductive therapy was related to decrease in leukocyte count during the disease course.Conclusions:We validate the reproducibility of IPSET-thrombosis in Chinese ET patients and provide key clinical implications. Background:Somatic JAK2V617F mutation exists in about50-60%of patients with essential thrombocythemia (ET). Recently, discovery of calreticulin (CALR) mutations, which were found in about half of ET patients with wild type JAK2, fills the molecular diagnostic gap. However, the prevalence of CALR mutations has not been reported in Asian patients, and its therapeutic implications have not yet been evaluated.Objectives:We studied profiles of specific mutations in Chinese ET patients to provided additional details on the utility of CALR mutations in the diagnosis, prognosis and treatment of ET.Methods:We retrospectively evaluated the clinical characteristics in436Chinese patients diagnosed with ET in our hospital from1990to2013. Mutations in JAK2V617F, MPL exon10and CALR exon9were analyzed in all of the patients. Real-time quantitative PCR assay was performed to detect JAK2V617F mutation. Mutations in CALR and MPL were assessed by bidirectional sequencing. Each type of deletions or insertions in CALR was cloned by the TA cloning system. Cox proportional hazards regression was employed to carry out univariate survival analysis, and factors that were significant were forced to multivariate survival analysis. Thrombosis-free survival was estimated by Kaplan-Meier method, and log-rank test was used to compare thrombosis-free survival data.Results:Compared with Caucasian patients, Chinese patients had a lower frequency of MPL mutations (1.4%) but comparable JAK2V617F (55.1%) and CALR mutations (22.7%). We found5new types of deletions or insertions in CALR. Two patients harbored both JAK2V617F and CALR mutations; one of whom had a novel point mutation in CALR exon9(c.997C>T). Absence of the point mutation in T cells confirmed the mutation to be somatic. Compared with V617F+patients, CALR-mutated patients displayed lower leukocyte count, granulocyte count, hemoglobin level, lower rate of positive EECs but higher platelet count (P<0.01for each comparison). Triple-negative patients had intermediate leukocyte count, hemoglobin level, platelet count and intermediate rate of positive EECs between V617F+and CALR-mutated patients. In multivariate analysis, JAK2V617F mutation was a risk factor regardless of whether thrombosis occurred at diagnosis (Hazard ratio=1.836; P=0.040) or during follow-up (Hazard ratio=2.678; P=0.023), but CALR mutation was not at either time. Kaplan-Meier analysis revealed a more favorable thrombosis-free survival in CALR-mutated patients than in V617F+cases (P=0.014), and the lower frequency of thrombosis in CALR-mutated patients was most likely due to the low thrombotic rate in type2CALR-mutated patients (7.9%). Although no difference concerning fibrotic transformation was found between CALR-mutated and V617F+ET (P=1.000), CALR-mutated patients had a higher degree of reticulin deposition (P=0.003). The difference was mostly ascribed to the higher rate of grade1reticulin deposition in type1CALR-mutated patients compared with V617F+patients. Screening for CALR mutations in paired samples before and after treatment indicated that CALR-mutated clones were not completely eliminated by cytoreductive treatment. Combination use of antiplatelet and cytoreductive agents decreased the risk of thrombosis in V617F+patients (P=0.034), but not in CALR-mutated cases (P=1.000). Conclusions:We confirm the value of CALR mutations in the diagnosis and prognosis of ET in Chinese patients and show the clinical correlates of type1and type2CALR muations. The present study provide new evidence for making treatment strategies based on molecular markers. Background:Essential thrombocythemia (ET) is extremely rare in children, and the clinical course of childhood ET remains unclear because of the small sample number. Further study with a large sample size is needed.Objectives:To evaluate the clinical manifestations, complications, treatment strategies and long-term outcomes in children diagnosed with ET.Methods:A cohort of70children diagnosed with ET (age≤18) were retrospectively evaluated.Results:The median age was12years (range2-18years) with a male predominance (male/female ratio,1.4). The gender distribution was different from adult ET patients. Most of children (54.3%) did not display thrombocytosis-related symptoms at diagnosis, and the presence of symptoms was positively related to platelet count (P=0.002). Compared with adult patients, children with ET had a lower frequency of JAK2V617F mutation (18.8%). Different from adult patiens, blood cell counts were not significantly different between patients with and without JAK2V617F mutation in childhood ET (P>0.05). Most of the symptoms related to thrombocytosis (82.6%) responded to antiplatelet or cytoreductive drugs. Resistance/intolerance existed in children receiving hydroxyurea, but none of them suffered from severe side effects or developed second malignancies during hydroxyurea treatment. Compared with adult patients, children with ET had a lower risk of thrombosis (1.4%). We reported the first case of ET with development of cavernous transformation of portal vein (CTPV) and transformation to overt fibrosis in the same child less than14years old. Two children (2.9%) transformed to overt fibrosis during follow-up, and increase in leukocyte count might predict the occurance of disease transformation.Conclusions:Clinical and molecular features in children with ET are different from adult ET patients. Background:Compared with adult patients, children with essential thrombocythemia (ET) had a lower frequency of JAK2V617F mutation. Most of the children did not harbor a well-known genetic marker, and the pathogenesis of childhood ET remains unclear.Objectives:To investigate molecular features and clonal evolution of childhood ET, and to provide primary evidence on understanding the pathogenesis of childhood ET.Methods:High-throughout targeted capture exome sequencing was used to explore mutations in55genes which were all related to hematologic neoplasms. All of the positive mutations were evaluated in100normal controls to exclude polymorphism. We speculated the clonal evolution based on allele frequency.Results:The mean depth was384×, with a mean coverage of99.6%. Validations of the mutations by Sanger sequencing revealed an accuracy of93.8%. Finally,16mutations were found in11genes and in13patients. All of the16mutations were not found in healthy controls. Different from adult ET, most of the mutations in children were germline mutations (56.3%), which might be one of the important mechanisms by which the onset of the disease occurred earlier in children. JAK2V617F was positive in6patients (18.8%), and the rate was lower than that in adult ET. None of the children displayed CALR-or MPL-mutated. JAK246/1haplotype was found in12children (60%). A list of mutations accompanied with JAK2V617F mutation, including mutations in ASXL1, U2AF1, NRAS and IDH1. Genes in the JAK-STAT pathway (45%) and with epigenetic functions were mostly involved (25%). Concurrent mutations in the above two groups of genes represented20%of the children. Clone evolution analysis based on allele frequency revealed that JAK2V617F might not be the driver mutation, but was an event secondary to other mutations. Conclusions:The mutational profile of childhood ET was different from adult ET. Germline mutations might be one of the important mechanisms by which the onset of the disease occurred earlier. JAK2V617F might be a secondary event.