Marta Bellini

JAK2 or CALR mutation status defines subtypes of essential thrombocythemia with substantially different clinical course and outcomes

Patients with essential thrombocythemia may carry JAK2 (V617F), an MPL substitution, or a calreticulin gene (CALR) mutation. We studied biologic and clinical features of essential thrombocythemia according to JAK2 or CALR mutation status and in relation to those of polycythemia vera. The mutant allele burden was lower in JAK2-mutated than in CALR-mutated essential thrombocythemia. Patients with JAK2 (V617F) were older, had a higher hemoglobin level and white blood cell count, and lower platelet count and serum erythropoietin than those with CALR mutation. Hematologic parameters of patients with JAK2-mutated essential thrombocythemia or polycythemia vera were related to the mutant allele burden. While no polycythemic transformation was observed in CALR-mutated patients, the cumulative risk was 29% at 15 years in those with JAK2-mutated essential thrombocythemia. There was no significant difference in myelofibrotic transformation between the 2 subtypes of essential thrombocythemia. Patients with JAK2-mutated essential thrombocythemia and those with polycythemia vera had a similar risk of thrombosis, which was twice that of patients with the CALR mutation. These observations are consistent with the notion that JAK2-mutated essential thrombocythemia and polycythemia vera represent different phenotypes of a single myeloproliferative neoplasm, whereas CALR-mutated essential thrombocythemia is a distinct disease entity.

Clinical effect of driver mutations of JAK2, CALR, or MPL in primary myelofibrosis

We studied the impact of driver mutations of JAK2, CALR, (calreticulin gene) or MPL on clinical course, leukemic transformation, and survival of patients with primary myelofibrosis (PMF). Of the 617 subjects studied, 399 (64.7%) carried JAK2 (V617F), 140 (22.7%) had a CALR exon 9 indel, 25 (4.0%) carried an MPL (W515) mutation, and 53 (8.6%) had nonmutated JAK2, CALR, and MPL (so-called triple-negative PMF). Patients with CALR mutation had a lower risk of developing anemia, thrombocytopenia, and marked leukocytosis compared with other subtypes. They also had a lower risk of thrombosis compared with patients carrying JAK2 (V617F). At the opposite, triple-negative patients had higher incidence of leukemic transformation compared with either CALR-mutant or JAK2-mutant patients. Median overall survival was 17.7 years in CALR-mutant, 9.2 years in JAK2-mutant, 9.1 years in MPL-mutant, and 3.2 years in triple-negative patients. In multivariate analysis corrected for age, CALR-mutant patients had better overall survival than either JAK2-mutant or triple-negative patients. The impact of genetic lesions on survival was independent of current prognostic scoring systems. These observations indicate that driver mutations define distinct disease entities within PMF. Accounting for them is not only relevant to clinical decision-making, but should also be considered in designing clinical trials.

Differential clinical effects of different mutation subtypes in CALR-mutant myeloproliferative neoplasms

A quarter of patients with essential thrombocythemia or primary myelofibrosis carry a driver mutation of CALR, the calreticulin gene. A 52-bp deletion (type 1) and a 5-bp insertion (type 2 mutation) are the most frequent variants. These indels might differentially impair the calcium binding activity of mutant calreticulin. We studied the relationship between mutation subtype and biological/clinical features of the disease. Thirty-two different types of CALR variants were identified in 311 patients. Based on their predicted effect on calreticulin C-terminal, mutations were classified as: (i) type 1-like (65%); (ii) type 2-like (32%); and (iii) other types (3%). Corresponding CALR mutants had significantly different estimated isoelectric points. Patients with type 1 mutation, but not those with type 2, showed abnormal cytosolic calcium signals in cultured megakaryocytes. Type 1-like mutations were mainly associated with a myelofibrosis phenotype and a significantly higher risk of myelofibrotic transformation in essential thrombocythemia. Type 2-like CALR mutations were preferentially associated with an essential thrombocythemia phenotype, low risk of thrombosis despite very-high platelet counts and indolent clinical course. Thus, mutation subtype contributes to determining clinical phenotype and outcomes in CALR-mutant myeloproliferative neoplasms. CALR variants that markedly impair the calcium binding activity of mutant calreticulin are mainly associated with a myelofibrosis phenotype.

CALR exon 9 mutations are somatically acquired events in familial cases of essential thrombocythemia or primary myelofibrosis

Somatic mutations in the calreticulin (CALR) gene were recently discovered in patients with sporadic essential thrombocythemia (ET) and primary myelofibrosis (PMF) lacking JAK2 and MPL mutations. We studied CALR mutation status in familial cases of myeloproliferative neoplasm. In a cohort of 127 patients, CALR indels were identified in 6 of 55 (11%) subjects with ET and in 6 of 20 (30%) with PMF, whereas 52 cases of polycythemia vera had nonmutated CALR. All CALR mutations were somatic, found in granulocytes but not in T lymphocytes. Patients with CALR-mutated ET showed a higher platelet count (P = .017) and a lower cumulative incidence of thrombosis (P = .036) and of disease progression (P = .047) compared with those with JAK2 (V617F). In conclusion, a significant proportion of familial ET and PMF nonmutated for JAK2 carry a somatic mutation of CALR.

A novel germline JAK2 mutation in familial myeloproliferative neoplasms.

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Efficacy of ruxolitinib in myeloid neoplasms with PCM1-JAK2 fusion gene.

Dear Editor, We read with interest the paper by Schwaab et al. published in September 2014 regarding two cases of myeloid neoplasms associated with PCM1-JAK2 and BCR-JAK2 fusion genes treated with ruxolitinib [1]. While they reported a very good initial response for both cases, relapse occurred after 18 and 24 months, respectively. The authors concluded that the response of myeloid disorders with JAK2 fusion genes to ruxolitinib is short lived, but that ruxolitinib may be an important bridging therapy prior to allogeneic bone marrow transplantation (ASCT). Our groups previously reported two cases of myeloid neoplasms/chronic eosinophilic leukemia (CEL) with a PCM1-JAK2 fusion gene who were treated with ruxolitinib after obtainment of their informed consent, and of whom we here report the further follow-up. Both cases achieved cytogenetic response, and we provide quantitative PCR data to support this (Fig. 1a, b, respectively). The first case (patient 1) was a 72-year-old male with a PCM1-JAK2-positive CEL who gradually obtained a complete cytogenetic remission over a period of 15 months of therapy with ruxolitinib at a dose of 10–20 mg bid [2]. The hematological course of this patient beyond 15 months, under continued treatment with ruxolitinib (10 mg bid) was uneventful, with moderate anemia (Hb>120 g/L) not requiring blood transfusions, with normal leukocytes and platelet counts and normal eosinophil counts. Consecutive cytogenetic and FISH studies on bone marrow showed complete cytogenetic remission (no aberrant metaphases at 33 months, 20 metaphases analyzed; normal interphase FISH, 200 nuclei analyzed). In addition, the measurement of disease burden by real-time quantitative RT-PCR showed a 2 log decrease at 34 months as compared with the disease burden at the start of ruxolitinib. The last reevaluation was done 3 months before his death due to unrelated cardiac problems (septic endocarditis) 36 months after the start of ruxolitinib, without evidence of relapse. The second case (patient 2) was a 31-year-old female affected with CEL [3]. She started ruxolitinib in 2011 at 15 mg bid and obtained a complete clinical remission. She obtained a complete cytogenetic remission at 46 months: at last evaluation, we did not observe aberrant metaphases (20 metaphases analyzed) and aberrant nuclei with t(8;9) (300 nuclei analyzed). A marked reduction of the PCM1JAK2 fusion transcript was detected. She is still alive in complete hematological remission after 46 months of treatment with Ruxolitinib. Both patients therefore achieved complete hematologic remission, complete cytogenetic response, and a marked * Elisa Rumi elisarumi@hotmail.com

LNK mutations in familial myeloproliferative neoplasms.

To the editor: Myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis, have in most instances a sporadic occurrence, but familial clustering of MPNs has been reported and familial cases are about 7% to 8% of all MPN patients

Impact of mutational status on pregnancy outcome in patients with essential thrombocytemia

Essential thrombocytemia (ET) may occur in women of childbearing age. Pregnancy may therefore be a common issue in the clinical management of young women with ET.[1][1],[2][2] Previous studies have shown live birth rates of 50% to 70% and spontaneous abortion rates of 25% to 50%, mostly during the

Clinical course and outcome of essential thrombocythemia and prefibrotic myelofibrosis according to the revised WHO 2016 diagnostic criteria

The recently revised World Health Organization (WHO) classification of myeloid neoplasms recognizes prefibrotic myelofibrosis (prePMF) as a distinct entity, characterized by well-defined histopathologic features together with minor clinical criteria (leukocytes, anemia, increased LDH, splenomegaly). The aim of the study was to examine the clinical relevance of distinguishing prePMF from essential thrombocythemia (ET). We identified in our database all patients affected with ET, prePMF and primary myelofibrosis (PMF) diagnosed according to 2008 WHO criteria with a bone marrow fibrosis grade 0-1 at diagnosis and one DNA sample to define the mutational status. The bone marrow morphology of all 404 identified patients was reviewed by an expert pathologist and patients were reclassified according to the 2016 WHO criteria. After reclassification, our cohort included 269 ET, 109 prePMF, and 26 myeloproliferative neoplasm unclassificable. In comparison with ET, patients with prePMF had higher leukocyte count, lower hemoglobin level, higher platelet count, higher LDH values, and higher number of circulating CD34-positive cells; they showed more frequently splenomegaly (all P values < ·001). CALR mutations were more frequent in prePMF than in ET (35·8% vs 17·8%, P < ·001). PrePMF patients had shorter overall survival (P < ·001) and a trend to a higher incidence of leukemic evolution (P ·067) compared to ET patients, while they did not differ in terms of thrombotic and bleeding complications. In conclusion, ET and prePMF diagnosed according to 2016 WHO criteria are two entities with a different clinical phenotype at diagnosis and a different clinical outcome.

Benefit-risk profile of cytoreductive drugs along with antiplatelet and antithrombotic therapy after transient ischemic attack or ischemic stroke in myeloproliferative neoplasms

We analyzed 597 patients with myeloproliferative neoplasms (MPN) who presented transient ischemic attacks (TIA, n = 270) or ischemic stroke (IS, n = 327). Treatment included aspirin, oral anticoagulants, and cytoreductive drugs. The composite incidence of recurrent TIA and IS, acute myocardial infarction (AMI), and cardiovascular (CV) death was 4.21 and 19.2%, respectively at one and five years after the index event, an estimate unexpectedly lower than reported in the general population. Patients tended to replicate the first clinical manifestation (hazard ratio, HR: 2.41 and 4.41 for recurrent TIA and IS, respectively); additional factors for recurrent TIA were previous TIA (HR: 3.40) and microvascular disturbances (HR: 2.30); for recurrent IS arterial hypertension (HR: 4.24) and IS occurrence after MPN diagnosis (HR: 4.47). CV mortality was predicted by age over 60 years (HR: 3.98), an index IS (HR: 3.61), and the occurrence of index events after MPN diagnosis (HR: 2.62). Cytoreductive therapy was a strong protective factor (HR: 0.24). The rate of major bleeding was similar to the general population (0.90 per 100 patient-years). In conclusion, the long-term clinical outcome after TIA and IS in MPN appears even more favorable than in the general population, suggesting an advantageous benefit-risk profile of antithrombotic and cytoreductive treatment.