Prognostic factors for thrombosis, myelofibrosis, and leukemia in essential thrombocythemia: a study of 605 patients

Background Essential thrombocythemia is a chronic myeloproliferative disorder; patients with this disorder have a propensity to develop thrombosis, myelofibrosis, and leukemia. Design and Methods We studied 605 patients with essential thrombocythemia (follow-up 4596 person-years) with the aim of defining prognostic factors for thrombosis, myelofibrosis, and leukemia during follow-up. Results Sixty-six patients (11%) developed thrombosis with a 10-year risk of 14%. Age >60 years ( p 60 years ( p =0.02) was significantly correlated with the development of leukemia. Cytotoxic treatment did not imply a higher risk of leukemia. At the time of the analysis, 64 of the 605 patients (10.6%) had died. The 10-year probability of survival was 88%, with a median survival of 22.3 years. Age >60 years ( p <0.001) and history of thrombosis ( p =0.001) were independent risk factors for survival. Conclusions The findings from this study on a large series of patients treated according to current clinical practice provide reassurance that essential thrombocythemia is an indolent disorder and affected patients have a long survival. The main risk is thrombosis, while myelofibrosis and leukemia are rare and late complications

Increased risk of pregnancy complications in patients with essential thrombocythemia carrying the JAK2 (617V>F) mutation

Abstract Essential thrombocythemia (ET) may occur in women of childbearing age. To investigate the risk of pregnancy complications, we studied 103 pregnancies that occurred in 62 women with ET. The 2-tailed Fisher exact test showed that pregnancy outcome was independent from that of a previous pregnancy. The rate of live birth was 64%, and 51% of pregnancies were uneventful. Maternal complications occurred in 9%, while fetal complications occurred in 40% of pregnancies. The Mantel-Haenszel method showed that fetal loss in women with ET was 3.4-fold higher (95% confidence interval [CI]: 3-3.9; P F) mutation, and a multivariate logistic regression model identified this mutation as an independent predictor of pregnancy complications (P = .01). Neither the platelet count nor the leukocyte count was a risk factor. JAK2 (617V>F)–positive patients had an odds ratio of 2.02 (95% CI: 1.1 - 3.8) of developing complications in comparison with JAK2 (617V>F)–negative patients. Aspirin did not prevent complication in JAK2 (617V>F)–positive patients and appeared to worsen outcome in JAK2 (617V>F)–negative patients. A relationship was found between JAK2 (617V>F) and fetal loss (P = .05). This study indicates that patients carrying the JAK2 (617V>F) mutation have higher risk of developing pregnancy complications

Increased risk of lymphoid neoplasm in patients with myeloproliferative neoplasm: a study of 1,915 patients

Within a cohort of 1,915 consecutive patients with myeloproliferative neoplasm followed for a median time of 5.2 years (range 0–33.3), we investigated the occurrence of lymphoid neoplasm with the aim of defining this risk and to investigate the role of genetic predisposing factors. We identified 22 patients with myeloproliferative neoplasm who developed lymphoid neoplasm over their lifetime. We found that the risk of developing lymphoid neoplasm was 2.79-fold higher (95% CI, 1.80–4.33; P<0.001) than that of the general Italian population. A tag SNP surrogate for JAK2 GGCC haplotype was used to clarify a potential correlation between lymphoid-myeloid neoplasm occurrence and this genetic predisposing factor. As we did not find any difference in GGCC haplotype frequency between patients with both myeloid and lymphoid neoplasm and patients with myeloid neoplasm, JAK2 GGCC haplotype should not be considered a genetic predisposing factor. No difference in familial clustering was observed between the two groups

The role of the JAK2 GGCC haplotype and the TET2 gene in familial myeloproliferative neoplasms

Background Myeloproliferative neoplasms constitute a group of diverse chronic myeloid malignancies that share pathogenic features such as acquired mutations in the JAK2, TET2, CBL and MPL genes. There are recent reports that a JAK2 gene haplotype (GGCC or 46/1) confers susceptibility to JAK2 mutation-positive myeloproliferative neoplasms. The aim of this study was to examine the role of the JAK2 GGCC haplotype and germline mutations of TET2, CBL and MPL in familial myeloproliferative neoplasms. Design and Methods We investigated patients with familial (n=88) or sporadic (n=684) myeloproliferative neoplasms, and a control population (n=203) from the same demographic area in Italy. Association analysis was performed using tagged single nucleotide polymorphisms (rs10974944 and rs12343867) of the JAK2 haplotype. Sequence analysis of TET2, CBL and MPL was conducted in the 88 patients with familial myeloproliferative neoplasms. Results Association analysis revealed no difference in haplotype frequency between familial and sporadic cases of myeloproliferative neoplasms (P=0.6529). No germline mutations in TET2, CBL or MPL that segregate with the disease phenotype were identified. As we observed variability in somatic mutations in the affected members of a pedigree with myeloproliferative neoplasms, we postulated that somatic mutagenesis is increased in familial myeloproliferative neoplasms. Accordingly, we compared the incidence of malignant disorders between sporadic and familial patients. Although the overall incidence of malignant disorders did not differ significantly between cases of familial and sporadic myeloproliferative neoplasms, malignancies were more frequent in patients with familial disease aged between 50 to 70 years (P=0.0198) than in patients in the same age range with sporadic myeloproliferative neoplasms. Conclusions We conclude that the JAK2 GGCC haplotype and germline mutations of TET2, CBL or MPL do not explain familial clustering of myeloproliferative neoplasms. As we observed an increased frequency of malignant disorders in patients with familial myeloproliferative neoplasms, we hypothesize that the germline genetic lesions that underlie familial clustering of myeloproliferative neoplasms predispose to somatic mutagenesis that is not restricted to myeloid hematopoietic cells but cause an increase in overall carcinogenesis

Mutation Type As a Major Determinant of Clinical Phenotype in Myeloproliferative Neoplasms Associated with Mutant Calreticulin

About 25% of patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF) carry a somatic mutation of CALR, the calreticulin gene [N Engl J Med. 2013;369:2379-90]. So far, more than 50 different indels in CALR exon 9 have been found, but a 52-bp deletion (type 1 mutation) and a 5-bp insertion (type 2) are the most common lesions. All indels generate a novel C-terminus of the mutant protein, in which the endoplasmic reticulum retention signal KDEL is lost and the negatively charged amino acids are replaced by neutral and positively charged amino acids, disrupting the Ca-binding site. This suggests that both cellular dislocation and impaired Ca-binding activity may be involved in the abnormal proliferation of cells expressing a mutant calreticulin. It is still unclear, however, why the same mutant gene is associated with 2 different disease phenotypes (ET and PMF). In particular, little in known about the effect of the mutant protein on megakaryocyte biology and bone marrow collagen deposition. We studied the relationships between CALR mutation type, megakaryocyte biology, and clinical phenotype in patients with myeloproliferative neoplasms. According to the 2008 WHO criteria, 716 out of 892 patients had ET and 176 had PMF. Overall, 578 (65%) patients carried JAK2 (V617F), 230 (26%) had a CALR indel, and 84 (9%) had nonmutated JAK2 and CALR. Patients with MPL mutations were excluded. Twenty-six different types of CALR lesions were identified: 120 (52%) patients had type 1 mutation, 75 (33%) had type 2, and 35 (15%) carried other indels. The frequency of type 1 mutation was significantly higher in PMF than in ET (71% vs 46%, P=.004). All these variants involved 3 different stretches of negatively charged amino acids, with an increase in the isoelectric points (pI) of the mutant protein. As type 1 and type 2 mutations affected stretch I and III, respectively, the 26 indels were categorized into 3 groups on the basis of the stretch they affected: i) type 1-like (61%), affecting stretch I; ii) type 2-like (36%), stretch III; iii) and other types (3%), stretch II. The pI values were significantly different in the 3 groups (P<.001). The frequency of type-1 like mutations was significantly higher in PMF than in ET (82% vs 55%, P=.001). In vitro differentiated megakaryocytes from CALR-mutant patients displayed a significant increase in the extent of both intracellular Ca2+ release from the endoplasmic reticulum and extracellular Ca2+ entry inside the cytoplasm, as compared with healthy controls. Megakaryocytes carrying type 1-like CALR mutations exhibited the highest amplitude of Ca2+ flows regardless of the type of disease. In ET, impaired Ca2+ homeostasis was accompanied by atypical proplatelet architecture (ie, more branches and bifurcations). With respect to clinical phenotype at diagnosis, ET patients with type 2-like CALR mutation showed a trend towards higher PLT count (P=.063) and lower age (P=.053), and significantly lower LDH values (P=.021) than those with type 1-like mutation. In a hierarchical cluster analysis including demographic, clinical and molecular data, CALR mutation type (1 vs 2) identified the 2 clusters with the highest dissimilarity. Considering all patients, those with type 2-like CALR lesions had a better survival than those with JAK2 (V617F) (96.1% vs 84.4% at 10 years, P=.039), while no difference was found between the 2 CALR mutation types. ET patients with type 2-like CALR mutations showed a lower risk of thrombosis than those with JAK2 (V617F) (P=.010). By contrast, ET patients with type 1-like CALR mutations had a higher risk of myelofibrotic transformation that those with type 2-like CALR mutations (P=.029) and especially those with JAK2 (V617F) (P=.011). Finally, PMF patients with type 1-like CALR variants had a better survival than those with JAK2 (V617F) (80.1% vs 48% at 10 years, P=.008). In summary, abnormalities in megakaryocyte calcium metabolism and proplatelet architecture are found in patients with CALR-mutant myeloproliferative neoplasms, and their extent is related to mutation type. Type 2-like CALR mutations are more likely to be associated with isolated thrombocytosis without bone marrow fibrosis, ie, with an ET phenotype. By contrast, type 1-like CALR mutations are generally associated with bone marrow fibrosis, ie, with a PMF phenotype. Thus, in CALR-mutant myeloproliferative neoplasms, the mutation type is a major determinant of the clinical phenotype