Elisabetta Antonioli

Survival and Disease Progression in Essential Thrombocythemia Are Significantly Influenced by Accurate Morphologic Diagnosis: An International Study

PURPOSE The WHO diagnostic criteria underscore the role of bone marrow (BM) morphology in distinguishing essential thrombocythemia (ET) from early/prefibrotic primary myelofibrosis (PMF). This study examined the clinical relevance of such a distinction. METHODS Representatives from seven international centers of excellence for myeloproliferative neoplasms convened to create a clinicopathologic database of patients previously diagnosed as having ET (N = 1,104). Study eligibility criteria included availability of treatment-naive BM specimens obtained within 1 year of diagnosis. All bone marrows subsequently underwent a central re-review. RESULTS Diagnosis was confirmed as ET in 891 patients (81%) and was revised to early/prefibrotic PMF in 180 (16%); 33 patients were not evaluable. In early/prefibrotic PMF compared with ET, the 10-year survival rates (76% and 89%, respectively) and 15-year survival rates (59% and 80%, respectively), leukemic transformation rates at 10 years (5.8% and 0.7%, respectively) and 15 years (11.7% and 2.1%, respectively), and rates of progression to overt myelofibrosis at 10 years (12.3% and 0.8%, respectively) and 15 years (16.9% and 9.3%) were significantly worse. The respective death, leukemia, and overt myelofibrosis incidence rates per 100 patient-years for early/prefibrotic PMF compared with ET were 2.7% and 1.3% (relative risk [RR], 2.1; P < .001), 0.6% and 0.1% (RR, 5.2; P = .001), and 1% and 0.5% (RR, 2.0; P = .04). Multivariable analysis confirmed these findings and also identified age older than 60 years (hazard ratio [HR], 6.7), leukocyte count greater than 11 × 10(9)/L (HR, 2.01), anemia (HR, 2.95), and thrombosis history (HR, 2.81) as additional risk factors for survival. Thrombosis and JAK2V617F incidence rates were similar between the two groups. Survival in ET was similar to the sex- and age-standardized European population. CONCLUSION This study validates the clinical relevance of strict adherence to WHO criteria in the diagnosis of ET and provides important information on survival, disease complication rates, and prognostic factors in strictly WHO-defined ET and early/prefibrotic PMF.

Prospective identification of high-risk polycythemia vera patients based on JAK2(V617F) allele burden.

The aim of this study was to determine whether the burden of JAK2V617F allele correlated with major clinical outcomes in patients with polycythemia vera (PV). To this end, we determined JAK2 mutant allele levels in granulocytes of 173 PV patients at diagnosis. The mean (±s.d.) mutant allele burden was 52% (±29); 32 patients (18%) had greater than 75% mutant allele. The burden of JAK2V617F allele correlated with measurements of stimulated erythropoiesis (higher hematocrit, lower mean cell volume, serum ferritin and erythropoietin levels) and myelopoiesis (higher white cell count, neutrophil count and serum lactate dehydrogenase) and with markers of neutrophil activation (elevated leukocyte alkaline phosphatase and PRV-1 expression). As compared to those with less than 25% mutant allele, patients harboring greater than 75% JAK2V617F allele were at higher relative risk (RR) of presenting larger spleen (RR 4.7; P<0.001) or suffering from pruritus (RR 3.1; P<0.001). In these patients, the risk of requiring chemotherapy (RR 1.8; P=0.001) or developing major cardiovascular events (RR 7.1; P=0.003) during follow up were significantly increased. We conclude that a burden of JAK2V617F allele greater than 75% at diagnosis points to PV patients with high-risk disease.

Clinical correlates of JAK2V617F presence or allele burden in myeloproliferative neoplasms: a critical reappraisal

JAK2 and MPL mutations are recurrent in myeloproliferative neoplasms (MPNs). A JAK2 mutation, primarily JAK2V617F, is almost invariably associated with polycythemia vera (PV). However, JAK2V617F also occurs in the majority of patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF) as well as in a much smaller percentage of those with other MPNs. The mechanism(s) behind this one allele-multiple phenotypes phenomenon has not been fully elucidated. The issue is further confounded by the presence of marked variation in JAK2V617F allele burden among mutation-positive patients. In the current communication, we discuss potential mechanisms for phenotypic diversity among JAK2V617F-positive MPNs as well as review the current literature in regard to genotype–phenotype correlations (that is clinical correlates and prognostic significance) in the context of both the presence or absence of the mutation (ET and PMF) and its allele burden (PV, ET and PMF).

Clinical implications of the JAK2 V617F mutation in essential thrombocythemia.

istic upmodulation of CD20 and downmodulation of CD10, comparable to the immunophenotypic modulation observed in vivo. In contrast, the viable 7-AAD-negative cells retained their original immunophenotype (Figure 2e, f). For each antibody, the MFI differed between the viable and dead cells, but within these two populations the MFI was not affected by the type and dose of the cytotoxic agents to which the cells were exposed (data not shown). Further analysis of dead and viable cells showed that dead cells had a higher MFI for each isotype control antibody than viable cells. This increase in background staining was comparable to the upmodulation of CD20 on CD20-negative leukemic cells observed in day 15 and 28 samples. Altogether, these data indicate that the immunophenotypic modulation observed in vitro is due to the induction of cell kill, resulting in a higher aspecific staining and a decreased expression of membrane antigens. Our data suggest that in ALL patients undergoing treatment, immunophenotypic modulation is caused by drug-induced cell death, resulting in loss of membrane antigens and higher aspecific staining. Our data are in agreement with a recent study, which showed that the loss of expression of lineage antigens (such as CD19) is a common feature of lymphocytes undergoing apoptosis and that the MFI for different antigens might drop to undetectable levels during different stages of apoptosis. Antigens coexpressed on the same cells showed different degrees of loss in the different stages of apoptosis, suggesting that it is a specific, active process, rather than a general degradation of cell components. Our observation that immunophenotypic modulation is due to apoptotic cells also explains why ALL blast cells in resistant patients show no modulation. In conclusion, our data indicate that immunophenotypic modulation in ALL patients undergoing treatment can (at least in part) be explained by the induction of cell death. As the presence of these dying cells may still be clinically relevant, usage of strict gating procedures, based on the exact immunophenotype of the blast cells at diagnosis, should be avoided for the analysis of MRD.

Risk factors for arterial and venous thrombosis in WHO-defined essential thrombocythemia: an international study of 891 patients

In an international collaborative study, a central histologic review identified 891 patients with essential thrombocythemia, strictly defined by World Health Organization criteria. After a median follow-up of 6.2 years, 109 (12%) patients experienced arterial (n = 79) or venous (n = 37) thrombosis. In multivariable analysis, predictors of arterial thrombosis included age more than 60 years (P = .03; hazard ratio [HR] = 1.7), thrombosis history (P = .003; HR = 2.1), cardiovascular risk factors including tobacco use, hypertension, or diabetes mellitus (P = .007; HR = 1.9), leukocytosis (> 11 × 10(9)/L; P = .04; HR = 1.7), and presence of JAK2V617F (P = .009; HR = 2.6). In contrast, only male gender predicted venous thrombosis. Platelet count more than 1000 × 10(9)/L was associated with a lower risk of arterial thrombosis (P = .007; HR = 0.4). These associations, except the one with leukocytosis, remained significant (or near significant) when analysis was restricted to JAK2V617F-positive cases. The current study clarifies the contribution of specific disease and host characteristics to the risk of arterial versus venous thrombosis in essential thrombocythemia.

Characteristics and clinical correlates of MPL 515W>L/K mutation in essential thrombocythemia.

Among 994 patients with essential thrombocythemia (ET) who were genotyped for the MPLW515L/K mutation, 30 patients carrying the mutation were identified (3.0%), 8 of whom also displayed the JAK2V671F mutation. MPLW515L/K patients presented lower hemoglobin levels and higher platelet counts than did wild type (wt) MPL; these differences were highly significant compared with MPLwt/JAK2V617F-positive patients. Reduced hemoglobin and increased platelet levels were preferentially associated with the W515L and W515K alleles, respectively. MPL mutation was a significant risk factor for microvessel disturbances, suggesting platelet hyperreactivity associated with constitutively active MPL; arterial thromboses were increased only in comparison to MPLwt/JAK2wt patients. MPLW515L/K patients presented reduced total and erythroid bone marrow cellularity, whereas the numbers of megakaryocytes, megakaryocytic clusters, and small-sized megakaryocytes were all significantly increased. These data indicate that MPLW515L/K mutations do not define a distinct phenotype in ET, although some differences depended on the JAK2V617F mutational status of the counterpart.

Identification of patients with poorer survival in primary myelofibrosis based on the burden of JAK2V617F mutated allele.

A total of 186 patients with primary myelofibrosis (PMF) were genotyped for JAK2V617F at diagnosis aimed at analyzing the correlation of mutational status and mutated allele burden with outcome variables, including time to anemia, leukocytosis, leukopenia, thrombocytopenia, massive splenomegaly, leukemia, and with overall survival. A total of 127 JAK2V617F-mutated patients (68% of whole series) were divided in quartiles of V617F allele burden. After a median follow-up of 17.2 months, 23 patients died, 15 because of leukemia. A JAK2V617F mutated status did not impact on the rate of leukemia transformation or overall survival. Patients in the lower quartile had shorter time to anemia and leukopenia and did not progress to large splenomegaly. Furthermore, survival was significantly reduced in the lower quartile compared with upper quartiles and JAK2 wild-type patients. In multivariate analysis, factors associated with reduced survival were age, a blast count more than 1%, and a JAK2V617F burden within first quartile. Causes of death in the lower quartile were represented mainly by systemic infections. We conclude that a low JAK2V617F allele burden at diagnosis is preferentially associated with a myelodepletive rather than myeloproliferative phenotype and represents an independent factor associated with shortened survival in patients with PMF.

Leukocytosis and Risk Stratification Assessment in Essential Thrombocythemia

PURPOSE Established risk factors for thrombosis in essential thrombocythemia (ET) include age and previous vascular events. We aimed to refine this risk stratification by adding baseline leukocytosis. PATIENTS AND METHODS We enrolled 657 patients with ET followed for a median of 4.5 years who developed 72 major thrombosis. Cox proportional hazard model was performed to analyze the thrombotic risk and to discriminate ET patients with or without thrombosis, multivariable C statistic index was used. We searched for leukocytes cutoff with the best sensitivity and specificity by a receiver operating characteristic curve. RESULTS Results confirmed that age and prior events are independent risk factors for thrombosis and showed a gradient between baseline leukocytosis and thrombosis. On the contrary, no significant association was found either for JAK2(V617F) allele burden and for other laboratory parameters, including platelet number. In the model with conventional risk factors alone, C statistic ratio for total thrombosis was 0.63 and when leukocytosis was added, the change was small (C = 0.67). In contrast, in younger and asymptomatic patients (low-risk category), C statistic value indicated an high risk for thrombosis in patients with leukocytosis, similar to that calculated in conventionally defined high-risk group (C = 0.65). The best leukocyte cutoff values for predicting the events was found to be 9.4 (x 10(9)/L). CONCLUSION We suggest to include baseline leukocytosis in the risk stratification of ET patients enrolled in clinical trials.

Anaemia characterises patients with myelofibrosis harbouring MplW515L/K mutation

The clinical and haematological phenotype of patients with myelofibrosis harbouring MPLW515L/K mutation has not been thoroughly investigated. Of 217 myelofibrosis subjects, 18 (8·2%) had an MPL mutation, four of which (22%) co‐existed with JAK2V617F mutation. When compared with MPL wild‐type patients, irrespective of JAK2V617F status, those with MPLW515L/K, were more frequently female, were older (61 years vs. 57 years; P = 0·02), presented with more severe anaemia (haemoglobin, 101 g/l vs. 121 g/l; P = 0·002) and were more likely to require regular transfusional support (P = 0·012). These data indicate that MPL mutation in myelofibrosis characterises patients with more severe anaemic phenotype.

A prognostic model to predict survival in 867 World Health Organization–defined essential thrombocythemia at diagnosis: a study by the International Working Group on Myelofibrosis Research and Treatment

Diagnosis of essential thrombocythemia (ET) has been updated in the last World Health Organization (WHO) classification. We developed a prognostic model to predict survival at diagnosis, named IPSET (International Prognostic Score for ET), studying patients with WHO-defined ET. Age 60 years or older, leukocyte count ≥ 11 × 10(9)/L, and prior thrombosis significantly affected survival, by multivariable Cox regression. On the basis of the hazard ratio, we assigned 2 points to age and 1 each to leukocyte count and thrombosis. So, the IPSET model allocated 867 patients into 3 risk categories with significantly different survival: low (sum of points = 0; median survival not reached), intermediate (sum = 1-2; median survival 24.5 years), and high (sum = 3-4, median survival 13.8 years). The IPSET model was further validated in 2 independent cohorts including 132 WHO-defined ET and 234 Polycythemia Vera Study Group-defined ET patients. The IPSET model was able to predict the occurrence of thrombosis, and not to predict post-ET myelofibrosis. In conclusion, IPSET, based on age ≥ 60 years, leukocyte count ≥ 11 × 10(9)/L, and history of thrombosis allows prognostic assessment of WHO-defined ET and the validation process makes IPSET applicable in all patients phenotypically appearing as ET.