Circulating cell-free DNA improves the molecular characterisation of Ph-negative myeloproliferative neoplasms.

Genetic studies in patients with Philadelphia-negative myeloproliferative neoplasms (MPNs) are essential to establish the correct diagnosis and to optimise their management. Recently, it has been demonstrated that it is possible to detect molecular alterations analysing cell-free DNA (cfDNA) in plasma samples, which is known as liquid biopsy. We have assessed the molecular profile of a cohort of 107 MPN patients [33 polycythaemia vera (PV), 56 essential thrombocythaemia (ET), 14 primary myelofibrosis (PMF) and 4 unclassifiable MPN] by next-generation sequencing (NGS) using cfDNA and paired granulocyte DNA. A high concentration of cfDNA in plasma was observed in patients with high molecular complexity, in MPL-mutated cases, and in PMF patients. Targeted sequencing of cfDNA showed a comparable mutational profile (100% accuracy) to the one obtained in granulocytic DNA and a strong correlation was observed between the variant allele frequency (VAF) of gene mutations in both DNA sources. The median VAF detected in cfDNA (29·0%; range: 0·95-91·73%) was significantly higher than the VAF detected in granulocytes (median 25·2%; range: 0·10-95·5%), especially for MPL mutations (44·3% vs. 22·5%). In conclusion, our data support the use of cfDNA as a fast, sensitive and accurate strategy for performing molecular characterisation of MPN patients.

Thromboembolic events in polycythemia vera.

Thromboembolic events and cardiovascular disease are the most prevalent complications in patients with polycythemia vera (PV) compared with other myeloproliferative disorders and are the major cause of morbidity and mortality in this population. Moreover, a vascular complication such as arterial or venous thrombosis often leads to the diagnosis of PV. The highest rates of thrombosis typically occur shortly before or at diagnosis and decrease over time, probably due to the effects of treatment. Important risk factors include age (≥ 60 years old) and a history of thrombosis; elevated hematocrit and leukocytosis are also associated with an increased risk of thrombosis. The goal of therapy is to reduce the risk of thrombosis by controlling hematocrit to < 45%, a target associated with reduced rates of cardiovascular death and major thrombosis. Low-risk patients (< 60 years old with no history of thrombosis) are managed with phlebotomy and low-dose aspirin, whereas high-risk patients (≥ 60 years old and/or with a history of thrombosis) should be treated with cytoreductive agents. Interferon and ruxolitinib are considered second-line therapies for patients who are intolerant of or have an inadequate response to hydroxyurea, which is typically used as first-line therapy. In this review, we discuss factors associated with thrombosis and recent data on current treatments, including anticoagulation, highlighting the need for more controlled studies to determine the most effective cytoreductive therapies for reducing the risk of thrombosis in patients with PV.

Study of the frequency and reasons for discontinuation of different lines of treatment in patients with multiple myeloma.

The availability of new agents for the treatment of multiple myeloma has allowed the use of multiple lines of treatment, but a percentage of patients do not reach to receive this combination because of toxicity and early death. In this regard, a cross-sectional European study evaluated the management of different lines and discontinuation of treatment in 7635 patients from seven countries in routine clinical practice, finding that 39% of European patients do not receive a second line and that only 4% of patients reach third line in Spain, a figure that is striking when comparing with the rest of the countries. We analyze the frequency and causes of treatment discontinuation in a series of 108 patients from a Spanish University hospital showing that the main reason for permanent treatment discontinuation after finishing first line was to have a response, while death due to disease progression accounted for the main reason in subsequent lines of therapy, with its frequency increasing according to the number of lines received. Additionally, in our longitudinal study, we estimated, using a competitive risk analysis, that 22% of patients would not receive a second line of therapy at 60 months and 47% would not reach third line, also at 60 months, showing a marked discrepancy with the results reported in the cross-sectional European study. Although based on limited data, our results suggest the convenience of validating the findings of cross-sectional studies conducted in large cohorts.

Treatment of essential thrombocythemia in Europe: a prospective long-term observational study of 3649 high-risk patients in the Evaluation of Anagrelide Efficacy and Long-term Safety study.

Evaluation of Anagrelide (Xagrid®) Efficacy and Long-term Safety, a phase IV, prospective, non-interventional study performed in 13 European countries enrolled high-risk essential thrombocythemia patients treated with cytoreductive therapy. The primary objectives were safety and pregnancy outcomes. Of 3721 registered patients, 3649 received cytoreductive therapy. At registration, 3611 were receiving: anagrelide (Xagrid®) (n=804), other cytoreductive therapy (n=2666), or anagrelide + other cytoreductive therapy (n=141). The median age was 56 vs. 70 years for anagrelide vs. other cytoreductive therapy. Event rates (patients with events/100 patient-years) were 1.62 vs. 2.06 for total thrombosis and 0.15 vs. 0.53 for venous thrombosis. Anagrelide was more commonly associated with hemorrhage (0.89 vs. 0.43), especially with anti-aggregatory therapy (1.35 vs. 0.33) and myelofibrosis (1.04 vs. 0.30). Other cytoreductive therapies were more associated with acute leukemia (0.28 vs. 0.07) and other malignancies (1.29 vs. 0.44). Post hoc multivariate analyses identified increased risk for thrombosis with prior thrombohemorrhagic events, age ≥65, cardiovascular risk factors, or hypertension. Risk factors for transformation were prior thrombohemorrhagic events, age ≥65, time since diagnosis, and platelet count increase. Safety analysis reflected published data, and no new safety concerns for anagrelide were found. Live births occurred in 41/54 pregnancies (76%). clinicaltrials.gov Identifier: 00567502.

Impact of genotype on leukaemic transformation in polycythaemia vera and essential thrombocythaemia.

The influence of driver mutations on leukaemic transformation was analysed in 1747 patients with polycythaemia vera or essential thrombocythaemia. With a median follow-up of 7·2 years, 349 patients died and 62 progressed to acute leukaemia or myelodysplastic syndrome. Taking death as a competing risk, CALR genotype was associated with a lower risk of transformation [subdistribution hazard ratio (SHR): 0·13, 95% confidence interval (CI): 0·2-0·9, P = 0·039], whereas JAK2 V617F showed borderline significance for higher risk (SHR: 2·05, 95% CI: 0·9-4·6, P = 0·09). Myelofibrotic transformation increased leukaemic risk, except in CALR-mutated patients. Next generation sequencing of 51 genes at the time of transformation showed additional mutations (median number: 3; range: 1-5) in 25 out of 29 (86%) assessable cases. Mutations (median: 1; range: 1-3) were detected in 67% of paired samples from the chronic phase. Leukaemia appeared in a JAK2 V617F negative clone in 17 (58%) cases, eleven of them being previously JAK2 V617F-positive. JAK2 V617F-mutated leukaemia was significantly associated with complex karyotype and acquisition of TP53 mutations, whereas EZH2 and RUNX1 mutations were more frequent in JAK2 V617F-negative leukaemia. Survival was longer in JAK2 V617F-unmutated leukaemia (343 days vs. 95 days, P = 0·003). In conclusion, CALR genotype is associated with a lower risk of leukaemic transformation. Leukaemia arising in a JAK2 V617F-negative clone is TP53 independent and shows better survival.

Risk of thrombosis according to need of phlebotomies in patients with polycythemia vera treated with hydroxyurea.

Hematocrit control below 45% is associated with a lower rate of thrombosis in polycythemia vera. In patients receiving hydroxyurea, this target can be achieved with hydroxyurea alone or with the combination of hydroxyurea plus phlebotomies. However, the clinical implications of phlebotomy requirement under hydroxyurea therapy are unknown. The aim of this study was to evaluate the need for additional phlebotomies during the first five years of hydroxyurea therapy in 533 patients with polycythemia vera. Patients requiring 3 or more phlebotomies per year (n=85, 16%) showed a worse hematocrit control than those requiring 2 or less phlebotomies per year (n=448, 84%). There were no significant differences between the two study groups regarding leukocyte and platelet counts. Patients requiring 3 or more phlebotomies per year received significantly higher doses of hydroxyurea than the remaining patients. A significant higher rate of thrombosis was found in patients treated with hydroxyurea plus 3 or more phlebotomies per year compared to hydroxyurea with 0-2 phlebotomies per year (20.5% vs. 5.3% at 3 years; P<0.0001). In multivariate analysis, independent risk factors for thrombosis were phlebotomy dependency (HR: 3.3, 95%CI: 1.5-6.9; P=0.002) and thrombosis at diagnosis (HR: 4.7, 95%CI: 2.3-9.8; P<0.0001). The proportion of patients fulfilling the European LeukemiaNet criteria of resistance/intolerance to hydroxyurea was significantly higher in the group requiring 3 or more phlebotomies per year (18.7% vs. 7.1%; P=0.001) mainly due to extrahematologic toxicity. In conclusion, phlebotomy requirement under hydroxyurea therapy identifies a subset of patients with increased proliferation of polycythemia vera and higher risk of thrombosis.

Associations between gender, disease features and symptom burden in patients with myeloproliferative neoplasms: an analysis by the MPN QOL International Working Group.

The myeloproliferative neoplasms, including polycythemia vera, essential thrombocythemia and myelofibrosis, are distinguished by their debilitating symptom profiles, life-threatening complications and profound impact on quality of life. The role gender plays in the symptomatology of myeloproliferative neoplasms remains under-investigated. In this study we evaluated how gender relates to patients' characteristics, disease complications and overall symptom expression. A total of 2,006 patients (polycythemia vera=711, essential thrombocythemia=830, myelofibrosis=460, unknown=5) were prospectively evaluated, with patients completing the Myeloproliferative Neoplasm-Symptom Assessment Form and Brief Fatigue Inventory Patient Reported Outcome tools. Information on the individual patients' characteristics, disease complications and laboratory data was collected. Consistent with known literature, most female patients were more likely to have essential thrombocythemia (48.6% versus 33.0%; P<0.001) and most male patients were more likely to have polycythemia vera (41.8% versus 30.3%; P<0.001). The rate of thrombocytopenia was higher among males than females (13.9% versus 8.2%; P<0.001) and males also had greater red-blood cell transfusion requirements (7.3% versus 4.9%; P=0.02) with shorter mean disease duration (6.4 versus 7.2 years, P=0.03). Despite there being no statistical differences in risk scores, receipt of most therapies or prior complications (hemorrhage, thrombosis), females had more severe and more frequent symptoms for most individual symptoms, along with overall total symptom score (22.8 versus 20.3; P<0.001). Females had particularly high scores for abdominal-related symptoms (abdominal pain/discomfort) and microvascular symptoms (headache, fatigue, insomnia, concentration difficulties, dizziness; all P<0.01). Despite complaining of more severe symptom burden, females had similar quality of life scores to those of males. The results of this study suggest that gender contributes to the heterogeneity of myeloproliferative neoplasms by influencing phenotypic profiles and symptom expression.

Distinct clustering of symptomatic burden among myeloproliferative neoplasm patients: retrospective assessment in 1470 patients.

Symptom burden in myeloproliferative neoplasms (MPNs) is heterogeneous even among patients within the same MPN diagnosis. Using cluster analysis from prospectively gathered symptom burden data in 1470 international patients with essential thrombocythemia (ET), polycythemia vera (PV), or myelofibrosis (MF), we assessed for the presence of clusters and relationship to disease features and prognosis. In MF (4 clusters identified), clusters significantly differed by Dynamic International Prognostic Scoring System (DIPSS) risk (P < .001), leukopenia (P = .009), thrombocytopenia (P < .001), and spleen size (P = .02). Although an association existed between clusters and DIPSS risk, high symptom burden was noted in some low and intermediate-1-risk MF patients. In PV (5 clusters identified), total symptom score increased across clusters (P < .001), but clusters did not significantly differ by PV risk or the risk assessment variable of age. Among ET patients (5 clusters identified), clusters differed by gender (P = .04), anemia (P = .01), and prior hemorrhage (P = .047). Total symptom score increased across clusters (P < .001), but clusters did not significantly differ by International Prognostic Score for ET risk including the risk assessment variables. Significant symptom heterogeneity exists within each MPN subtype, sometimes independent of disease features or prognosis.

Ruxolitinib versus best available therapy in patients with polycythemia vera: 80-week follow-up from the RESPONSE trial.

RESPONSE is an open-label phase 3 study evaluating the Janus kinase 1/Janus kinase 2 inhibitor ruxolitinib versus best available therapy for efficacy/safety in hydroxyurea-resistant or intolerant patients with polycythemia vera. This preplanned analysis occurred when all patients completed the Week 80 visit or discontinued. Objectives included evaluating the durability of the primary response (Week 32 phlebotomy-independent hematocrit control plus ≥35% spleen volume reduction), its components, and that of complete hematologic remission; and long-term safety. Median exposure was 111 weeks; 91/110 (82.7%) patients randomized to ruxolitinib remained on treatment. No patients continued best available therapy (98/112 [87.5%] crossed over to ruxolitinib, most at/soon after Week 32). At Week 32, primary response was achieved by 22.7% vs. 0.9% of patients randomized to ruxolitinib and best available therapy, respectively (hematocrit control, 60.0% vs. 18.8%; spleen response, 40.0% vs. 0.9%). The probability of maintaining primary and hematocrit responses for ≥80 weeks was 92% and 89%, respectively; 43/44 spleen responses were maintained until Week 80. Complete hematologic remission at Week 32 was achieved in 23.6% of ruxolitinib-randomized patients; the probability of maintaining complete hematologic remission for ≥80 weeks was 69%. Among ruxolitinib crossover patients, 79.2% were not phlebotomized, and 18.8% achieved a ≥35% reduction from baseline in spleen volume after 32 weeks of treatment. New or worsening hematologic laboratory abnormalities in ruxolitinib-treated patients were primarily grade 1/2 decreases in hemoglobin, lymphocytes, and platelets. The thromboembolic event rate per 100 patient-years was 1.8 with randomized ruxolitinib treatment vs. 8.2 with best available therapy. These data support ruxolitinib as an effective long-term treatment option for hydroxyurea-resistant or intolerant patients with polycythemia vera. This trial was registered at clinicaltrials.gov identifier: 01243944.

Antiplatelet therapy versus observation in low-risk essential thrombocythemia with a CALR mutation.

The role of antiplatelet therapy as primary prophylaxis of thrombosis in low-risk essential thrombocythemia has not been studied in randomized clinical trials. We assessed the benefit/risk of low-dose aspirin in 433 patients with low-risk essential thrombocythemia (271 with a CALR mutation, 162 with a JAK2(V617F) mutation) who were on antiplatelet therapy or observation only. After a follow up of 2215 person-years free from cytoreduction, 25 thrombotic and 17 bleeding episodes were recorded. In CALR-mutated patients, antiplatelet therapy did not affect the risk of thrombosis but was associated with a higher incidence of bleeding (12.9 versus 1.8 episodes per 1000 patient-years, P=0.03). In JAK2(V617F)-mutated patients, low-dose aspirin was associated with a reduced incidence of venous thrombosis with no effect on the risk of bleeding. Coexistence of JAK2(V617F)-mutation and cardiovascular risk factors increased the risk of thrombosis, even after adjusting for treatment with low-dose aspirin (incidence rate ratio: 9.8; 95% confidence interval: 2.3-42.3; P=0.02). Time free from cytoreduction was significantly shorter in CALR-mutated patients with essential thrombocythemia than in JAK2(V617F)-mutated ones (median time 5 years and 9.8 years, respectively; P=0.0002) and cytoreduction was usually necessary to control extreme thrombocytosis. In conclusion, in patients with low-risk, CALR-mutated essential thrombocythemia, low-dose aspirin does not reduce the risk of thrombosis and may increase the risk of bleeding.

Masked polycythaemia vera: presenting features, response to treatment and clinical outcomes.

Masked polycythaemia vera (PV) has been proposed as a new entity with poorer outcome than overt PV. In this study, the initial clinical and laboratory characteristics, response to treatment and outcome of masked and overt PV were compared using red cell mass and haemoglobin or haematocrit levels for the distinction between both entities. Sixty-eight of 151 PV patients (45%) were classified as masked PV according to World Health Organisation diagnostic criteria, whereas 16 (11%) were classified as masked PV using the British Committee for Standards in Haematology (BCSH). In comparison with overt PV, a higher platelet count and a lower JAK2V617F allele burden at diagnosis were observed in masked PV. Patients with masked PV needed lower phlebotomies and responded faster to hydroxcarbamide than those with overt PV. Complete haematological response was more frequently achieved in masked than in overt PV (79% vs. 58%, P = 0.001). There were no significant differences in the duration of haematological response, the rate of resistance or intolerance to hydroxycarbamide and the probability of molecular response according to type of PV (masked vs. overt). Overall survival, rate of thrombosis and major bleeding, and probability of transformation was superimposable among patients with masked and overt PV.

Revised response criteria for polycythemia vera and essential thrombocythemia: an ELN and IWG-MRT consensus project.

Standardized response criteria to interpret and compare clinical trials are needed for approval of new therapeutic agents by regulatory agencies. The European LeukemiaNet (ELN) response criteria for essential thrombocythemia (ET) and polycythemia vera (PV) issued in 2009 have been widely adopted as end points in a number of recent clinical trials. However, evidence exists that they do not predict response or provide clinically relevant measures of benefit for the patients. This article presents revised recommendations for assessing response in ET and PV provided by a working group established by ELN and International Working Group-Myeloproliferative Neoplasms Research and Treatment. New definitions of complete and partial remission incorporate clinical, hematological, and histological response assessments that include a standardized symptom assessment form and consider absence of disease progression and vascular events. We anticipate that these criteria will be adopted widely to facilitate the development of new and more effective therapies for ET and PV.

WHO-histological criteria for myeloproliferative neoplasms: reproducibility, diagnostic accuracy and correlation with gene mutations and clinical outcomes.

Bone marrow histology is included in the diagnostic criteria of myeloproliferative neoplasms (MPNs). However, some concerns have emerged about its reproducibility. To evaluate the diagnostic accuracy of histology and to assess its correlation with presence of mutations and clinical outcomes, two pathologists reviewed the bone marrow biopsies corresponding to 211 patients with MPN. Despite the low agreement in the evaluation of individual histopathological characteristics, the concordance among pathologists when establishing the diagnosis was good (Kappa index 0·67). The specificity of histology was 100%, 98·5% and 98% in polycythaemia vera (PV), essential thrombocythaemia (ET) and primary myelofibrosis (PMF), respectively, whereas the sensitivity of histological diagnosis was low in PV and ET (32·5% and 54% respectively) and acceptable in PMF (75%). Thirteen out of 146 (9%) patients with clinical ET were diagnosed as prefibrotic PMF. No histological agreement or MPN otherwise unspecified was more frequently observed in JAK2 V617F-positive ET than in CALR-mutated cases, whereas megakaryocytic abnormalities and prefibrotic PMF were more frequently observed in CALR-mutated ET. In conclusion, histological criteria of MPN have a limited diagnostic accuracy due to low sensitivity. Patients with JAK2 V617F-positive MPN have a heterogeneous histology while CALR-positive ET is associated with megakaryocyte abnormalities and prefibrotic PMF.

JAK2V617F homozygosity arises commonly and recurrently in PV and ET, but PV is characterized by expansion of a dominant homozygous subclone.

Subclones homozygous for JAK2V617F are more common in polycythemia vera (PV) than essential thrombocythemia (ET), but their prevalence and significance remain unclear. The JAK2 mutation status of 6495 BFU-E, grown in low erythropoietin conditions, was determined in 77 patients with PV or ET. Homozygous-mutant colonies were common in patients with JAK2V617F-positive PV and were surprisingly prevalent in JAK2V617F-positive ET and JAK2 exon 12-mutated PV. Using microsatellite PCR to map loss-of-heterozygosity breakpoints within individual colonies, we demonstrate that recurrent acquisition of JAK2V617F homozygosity occurs frequently in both PV and ET. PV was distinguished from ET by expansion of a dominant homozygous subclone, the selective advantage of which is likely to reflect additional genetic or epigenetic lesions. Our results suggest a model in which development of a dominant JAK2V617F-homzygous subclone drives erythrocytosis in many PV patients, with alternative mechanisms operating in those with small or undetectable homozygous-mutant clones.

Combination therapy of hydroxycarbamide with anagrelide in patients with essential thrombocythemia in the evaluation of Xagrid(R) efficacy and long-term safety study.

Available information is limited regarding the use of cytoreductive combination therapy in high-risk patients with essential thrombocythemia. This analysis aims to evaluate the clinical relevance and patterns of cytoreductive combination treatment in European high-risk patients with essential thrombocythemia in the Evaluation of Xagrid(®) Efficacy and Long-term Safety study. Of 3643 patients, 347 (9.5%) received combination therapy. Data were recorded at each 6-month update. Of 347 patients who received combination therapy, 304 (87.6%) received hydroxycarbamide + anagrelide. Monotherapies received before this combination were hydroxycarbamide (n=167, 54.9%) and anagrelide (n=123, 40.5%). Median weekly doses of hydroxycarbamide and anagrelide were: 7000 and 10.5 mg when used as prior monotherapy; 3500 and 7.0 mg when used as add-on treatment. Overall, median platelet counts were 581 × 10(9)/L and 411 × 10(9)/L before and after starting hydroxycarbamide + anagrelide, respectively. In patients with paired data (n=153), the number of patients with platelet counts less than 400 × 10(9)/L increased from 33 (21.6%) to 74 (48.4%; P<0.0001), and with platelet counts less than 600 × 10(9)/L, from 82 (53.6%) to 132 (86.3%; P<0.0001). Hydroxycarbamide + anagrelide was discontinued in 158 patients: 76 (48.1%) stopped hydroxycarbamide, 59 (37.3%) stopped anagrelide, 19 (12.0%) stopped both and 4 (2.5%) had another therapy added. The most frequent reasons for discontinuation were intolerance/side-effects, lack of efficacy, and therapeutic strategy. Combination therapy, usually hydroxycarbamide + anagrelide, is used in approximately 10% of all high-risk patients with essential thrombocythemia and may be a useful approach in treating patients for whom monotherapy is unsatisfactory. (Clinicaltrials.gov identifier:NCT00567502).

JAK2V617F monitoring in polycythemia vera and essential thrombocythemia: clinical usefulness for predicting myelofibrotic transformation and thrombotic events.

The JAK2V617F allele burden has been identified as a risk factor for vascular events and myelofibrotic transformation in polycythemia vera (PV) and essential thrombocythemia (ET). However, all previous studies have evaluated a single time point JAK2V617F measurement. Therefore, the frequency and the clinical significance of changes in the JAK2V617F mutant load occurring during the disease evolution remain unknown. In the present study, JAK2V617F monitoring was performed during the follow-up of 347 patients (PV = 163, ET = 184). According to their JAK2V617F evolutionary patterns, patients were stratified as stable < 50% (n = 261), stable ≥50% (n = 52), progressive increase (n = 24) and unexplained decrease (n = 10). After a 2,453 person-years follow-up, a total of 59 thrombotic events, 16 major hemorrhages, and 27 cases of myelofibrotic transformations were registered. At multivariate analyses, patients with a persistently high (≥50%) or unsteady JAK2V617F load during follow-up had an increased risk of myelofibrotic transformation (Incidence rate ratio [IRR]: 20.7, 95% CI: 6.5-65.4; P < 0.001) and a trend for a higher incidence of thrombosis (IRR: 1.7, 1-3.3; P = 0.05) than patients with a stable allele burden below 50%. In conclusion, JAK2V617F monitoring could be useful in patients with PV and ET for predicting disease's complications, especially myelofibrotic transformation.

Cytoreduction plus low-dose aspirin versus cytoreduction alone as primary prophylaxis of thrombosis in patients with high-risk essential thrombocythaemia: an observational study.

The effectiveness of low-dose aspirin in the primary prevention of thrombosis in patients with high-risk essential thrombocythaemia (ET) treated with cytoreductive drugs is not well established. The risk-benefit balance of low-dose aspirin plus cytoreductive therapy compared with cytoreduction alone was retrospectively analysed in 247 patients with high-risk ET without prior thrombosis. Follow-up was 763 and 685 person-years for cytoreduction plus low-dose aspirin and cytoreduction alone, respectively. The rate of thrombosis was not significantly reduced in patients on cytoreduction plus aspirin (14·4 events per 1000 person-years) when compared with those on cytoreduction alone (24·8 events per 1000 person-years; P = 0·2). However, in the subgroup of patients older than 60 years, the addition of low-dose aspirin was associated with a significantly lower rate of thrombosis (8·6 vs. 29·2 thrombosis per 1000 person-years for combined treatment and cytoreduction alone, respectively, P = 0·02). The rate of major bleeding was significantly higher with combined therapy than with cytoreduction alone both in the whole series (14·4 vs. 1·4 haemorrhagic events per 1000 person-years, respectively, P = 0·006) and in the subgroup of patients older than 60 years. In conclusion, low-dose aspirin benefits high-risk ET patients older than 60 years receiving cytoreductive therapy as primary prophylaxis of thrombosis.

Observation versus antiplatelet therapy as primary prophylaxis for thrombosis in low-risk essential thrombocythemia.

The effectiveness of antiplatelet therapy as primary prophylaxis for thrombosis in low-risk essential thrombocythemia (ET) is not proven. In this study, the incidence rates of arterial and venous thrombosis were retrospectively analyzed in 300 low-risk patients with ET treated with antiplatelet drugs as monotherapy (n = 198) or followed with careful observation (n = 102). Follow-up was 802 and 848 person-years for antiplatelet therapy and observation, respectively. Rates of thrombotic events were 21.2 and 17.7 per 1000 person-years for antiplatelet therapy and observation, respectively (P = .6). JAK2 V617F-positive patients not receiving antiplatelet medication showed an increased risk of venous thrombosis (incidence rate ratio [IRR]: 4.0; 95% CI: 1.2-12.9; P = .02). Patients with cardiovascular risk factors had increased rates of arterial thrombosis while on observation (IRR: 2.5; 95% CI: 1.02-6.1; P = .047). An increased risk of major bleeding was observed in patients with platelet count greater than 1000 x 10(9)/L under antiplatelet therapy (IRR: 5.4; 95% CI: 1.7-17.2; P = .004). In conclusion, antiplatelet therapy reduces the incidence of venous thrombosis in patients with JAK2-positive ET and the rate of arterial thrombosis in patients with associated cardiovascular risk factors. In the remaining low-risk patients, this therapy is not effective as primary prophylaxis of thrombosis, and observation may be an adequate option.

Red cell mass measurement in patients with clinically suspected diagnosis of polycythemia vera or essential thrombocythemia.

The cut off for hemoglobin or hematocrit that indicates the need for an isotopic red cell mass study was investigated in 179 patients with a presumptive diagnosis of polycythemia vera or essential thrombocythemia. Hematocrit showed better diagnostic accuracy than hemoglobin. Hemoglobin over 18.5 g/dL in males or over 16.5 g/dL in females showed a high specificity indicating that red cell mass study could be avoided in such cases, but it showed low sensitivity leading to 46% false negatives. The best value of hematocrit to indicate a red cell mass study was 0.50 L/L in males (specificity 75%, sensitivity 87.5%) and 0.48 L/L in females (specificity 73%, sensitivity 94%). Lowering the hematocrit threshold to 0.48 L/L in males increased sensitivity up to 95%. A red cell mass study should be performed in patients with suspected diagnosis of essential thrombocythemia or polycythemia vera and with hematocrit between 0.48 L/L and 0.52 L/L.