Disease correlates and clinical relevance of hereditary α-tryptasemia in patients with systemic mastocytosis.

BACKGROUND: Systemic mastocytosis (SM) encompasses a heterogeneous group of clonal disorders characterized by abnormal expansion of mast cells (MCs). Beyond KIT and other genes recurrently mutated in myeloid neoplasms, several genetic variants have been described as predisposing to the development of the disease and influencing its clinical phenotype. Increased copy number variants of the TPSAB1 gene were identified as a cause of nonclonal elevated tryptasemia and defined as hereditary α-tryptasemia (HαT). Moreover, HαT is enriched in patients with SM, where it can affect the incidence of mediator-related symptoms. OBJECTIVE: In a multicenter data set of 444 patients with MC disorders, we aimed to investigate the clinical correlates of germline TPSAB1 copy number gains. METHODS: Droplet digital PCR was performed in all cases to ascertain the presence of HαT. Clinical history along with blood values and bone marrow examination were analyzed. RESULTS: We confirmed a higher incidence of HαT+ cases (n = 59, 13.3%) in patients diagnosed with mastocytosis with respect to the general population (approximately 5%). HαT+ patients were characterized by a lower MC-associated disease burden and higher levels of tryptase. Several disease variables were coherent with this pattern, from bone marrow MC infiltration to MC-related histopathologic traits, which also accounted for a significantly higher incidence of clonal MC activation syndrome in HαT+ (10.2%) compared to HαT- (3.4%, P = .029) patients. We also confirmed that HαT+ carriers had a significantly higher frequency of anaphylaxis, without relevant differences for other clinical manifestations. CONCLUSION: These findings on a large patient series support and extend previous data, and suggest that knowledge of HαT status may be useful for personalized management of patients with SM.

Low bone mass and hypovitaminosis D in haemophilia: A single-centre study in patients with severe and moderate haemophilia A and B.

INTRODUCTION: Haemophilia (H) is frequently associated with a multifactorial reduction in bone mineral density (BDM), but little is known about possible differences between HA and HB according to their severity. AIM: To evaluate the association between low bone mineral density (BMD), 25-hydroxyvitamin D [25(OH)D] concentrations and bone turnover markers in patients with HA and HB younger or older than 50 years. METHODS: In 78 patients <50 years and 33 patients >50 years with severe (S) or moderate (M) HA and HB, BMD was measured by dual-energy X-ray absorptiometry at femoral neck (FN) and lumbar spine and then correlated to annual bleeding rate (ABR), World Federation of Haemophilia orthopaedic joint scale (WFH score), 25(OH)D concentrations, parathyroid hormone (PTH), amino-terminal telopeptide of type 1 collagen (NTx), urinary pyridinolines, osteocalcin and bone-specific alkaline phosphatase. RESULTS: Overall, a high prevalence of hypovitaminosis D was diagnosed. In patients <50 years, low FN-BMD was significantly more frequent in HA than in HB, while PTH, pyridinolines, ABR and WFH score were associated with H type and severity. In patients >50 years, similarly low FN-BMD was observed in HA and HB, while ABR and WFH score were associated with H type and severity, being milder in HB. CONCLUSIONS: Low bone mass is a frequent comorbidity in haemophilic patients of all ages, apart from those with MHB. Clinical and laboratory assessments confirm a higher bone impairment and faster bone resorption in HA compared with HB. Looking at H type and severity, MHB seems to have a normal bone metabolism and a less severe disease.

Splanchnic vein thromboses associated with myeloproliferative neoplasms: An international, retrospective study on 518 cases.

Myeloproliferative Neoplasms (MPN) course can be complicated by thrombosis involving unusual sites as the splanchnic veins (SVT). Their management is challenging, given their composite vascular risk. We performed a retrospective, cohort study in the framework of the International Working Group for MPN Research and Treatment (IWG-MRT), and AIRC-Gruppo Italiano Malattie Mieloproliferative (AGIMM). A total of 518 MPN-SVT cases were collected and compared with 1628 unselected, control MPN population, matched for disease subtype. Those with MPN-SVT were younger (median 44 years) and enriched in females compared to controls; PV (37.1%) and ET (34.4%) were the most frequent diagnoses. JAK2V617F mutation was highly prevalent (90.2%), and 38.6% of cases had an additional hypercoagulable disorder. SVT recurrence rate was 1.6 per 100 patient-years. Vitamin K-antagonists (VKA) halved the incidence of recurrence (OR 0.48), unlike cytoreduction (OR 0.96), and were not associated with overall or gastrointestinal bleeding in multivariable analysis. Esophageal varices were the only independent predictor for major bleeding (OR 17.4). Among MPN-SVT, risk of subsequent vascular events was skewed towards venous thromboses compared to controls. However, MPN-SVT clinical course was overall benign: SVT were enriched in PMF with lower IPSS, resulting in significantly longer survival than controls; survival was not affected in PV and slightly reduced in ET. MPN-U with SVT (n = 55) showed a particularly indolent phenotype, with no signs of disease evolution. In the to-date largest, contemporary cohort of MPN-SVT, VKA were confirmed effective in preventing recurrence, unlike cytoreduction, and safe; the major risk factor for bleeding was esophageal varices that therefore represent a major therapeutic target.

Myelodysplasia as assessed by multiparameter flow cytometry refines prognostic stratification provided by genotypic risk in systemic mastocytosis.

Systemic mastocytosis (SM) is characterized by extreme heterogeneity of manifestations and prognosis. Several disease-related biomarkers, including clinical, hematological and molecular variables, have been correlated with prognosis. Although relevant, the mutation profile closely reflects the WHO classification that has per se prognostic value. High-risk mutations (HRM) are largely confined to advanced forms, and thus fail in providing information regarding progression and outcome in the not-advanced variants. In this work, we studied hematopoietic cells by multi-parameter flow cytometry (MFC) in order to highlight dysplastic traits that might provide insights into outcome. A score previously validated for myelodysplastic syndromes, with high reproducibility in standard diagnostics, was used. The application of an MFC score to a cohort of 71 SM cases, concurrently genotyped for configuring a HRM category, resulted in the identification of two separate patients' categories (MFC+ and MFC-) characterized by significantly different clinical and laboratory features at presentation. The extent of dysplasia by MFC tended to parallel WHO-category and genotype-related stratification. MFC+ patients had shorter survival compared to MFC- ones, for whom the incidence of progression and/or death was virtually null. Of note, MFC score remained prognostically informative in unadvanced subsets. Furthermore, the integration of MFC and HRM was an independent predictor for outcome, also overcoming WHO-categories in multivariate analysis for EFS. Our results support the use of MFC analysis in the evaluation of patients with SM, alone and in combination with HRM, for refinement of prognosis assessment.

Inhibitors in Nonsevere Hemophilia A: What Is Known and Searching for the Unknown.

Nonsevere hemophilia A (NSHA) is an inherited X-linked bleeding disorder, caused by mutations of the F8 gene, leading to decreases of clotting factor VIII (FVIII) levels to 1 to 40 IU/dL. Desmopressin is the first therapeutic option for NSHA, but 40 to 50% of patients fail to attain adequate postinfusion FVIII levels. Thus, in these cases, FVIII concentrates remain the mainstay of treatment. The development of neutralizing FVIII antibodies (inhibitors) is a major challenge with replacement therapy. In contrast to severe disease, NSHA patients have a lifelong risk of inhibitor development. Recent data indicate that inhibitors are associated with a deterioration of clinical outcome, illustrated by an increase in bleeding and mortality rate. F8 genotype is an important risk factor for inhibitor occurrence together with surgical interventions and a high dose of FVIII concentrate. Adequate prevention and treatment of inhibitors in NSHA patients is limited by a lack of understanding of the underlying immunological mechanisms. Elucidation of the immunology driving inhibitor development is required to identify high-risk patients, to understand the association between clinical risk factors and inhibitor occurrence, and to provide the opportunity to develop new preventive and therapeutic strategies.

The Italian Mastocytosis Registry: 6-year experience from a hospital-based registry.

AIM: We collected 'real-life' data on the management of patients with mastocytosis in the Italian Mastocytosis Registry. METHODS: Six hundred patients diagnosed with mastocytosis between 1974 and 2014 were included from 19 centers. RESULTS: Among adults (n = 401); 156 (38.9%) patients were diagnosed with systemic mastocytosis. In 212 adults, no bone marrow studies were performed resulting in a provisional diagnosis of mastocytosis of the skin. This diagnosis was most frequently established in nonhematologic centers. In total, 182/184 pediatric patients had cutaneous mastocytosis. We confirmed that in the most patients with systemic mastocytosis, serum tryptase levels were >20 ng/ml and KIT D816V was detectable. CONCLUSION: The Italian Mastocytosis Registry revealed some center-specific approaches for diagnosis and therapy. Epidemiological evidence on this condition is provided.

Safety and efficacy of ruxolitinib in splanchnic vein thrombosis associated with myeloproliferative neoplasms.

Splanchnic vein thrombosis (SVT) is one of the vascular complications of myeloproliferative neoplasms (MPN). We designed a phase 2 clinical trial to evaluate safety and efficacy of ruxolitinib in reducing splenomegaly and improving disease-related symptoms in patients with MPN-associated SVT. Patients diagnosed with myelofibrosis (12 cases), polycythemia vera (5 cases) and essential thrombocythemia (4 cases) received ruxolitinib for 24 weeks in the core study period. Spleen volume was assessed by magnetic resonance imaging (MRI) and splanchnic vein circulation by echo-Doppler analysis. Nineteen patients carried JAK2V617F, one had MPLW515L, and one CALRL367fs*46 mutation. Eighteen patients had spleno-portal-mesenteric thrombosis, two had Budd-Chiari syndrome, and one had both sites involved; 16 patients had esophageal varices. Ruxolitinib was well tolerated with hematological toxicities consistent with those of patients without SVT and no hemorrhagic adverse events were recorded. After 24 weeks of treatment, spleen volume reduction ≥35% by MRI was achieved by 6/21 (29%) patients, and a ≥50% spleen length reduction by palpation at any time up to week 24 was obtained by 13/21 (62%) patients. At week 72, 8 of the 13 (62%) patients maintained the spleen response by palpation. No significant effect of treatment on esophageal varices or in splanchnic circulation was observed. MPN-related symptoms, evaluated by MPN-symptom assessment form (SAF) TSS questionnaire, improved significantly during the first 4 weeks and remained stable up to week 24. In conclusion, this trial shows that ruxolitinib is safe in patients with MPN-associated SVT, and effective in reducing spleen size and disease-related symptoms.

Impact of calreticulin mutations on clinical and hematological phenotype and outcome in essential thrombocythemia.

Mutations in the calreticulin (CALR) gene were recently discovered in patients with essential thrombocythemia (ET) lacking the JAK2V617F and MPLW515 mutations, but no information is available on the clinical correlates. In this series, CALR mutations were found in 15.5% of 576 World Health Organization-defined ET patients, accounting for 48.9% of JAK2 and MPL wild-type (wt) patients. CALR-mutated patients were preferentially male and showed higher platelet count and lower hemoglobin and leukocyte count compared with JAK2- and MPL-mutated patients. Patients carrying the CALR mutation had a lower risk of thrombosis than JAK2- and MPL-mutated patients; of interest, their risk was superimposable to patients who were wt for the above mutations. CALR mutation had no impact on survival or transformation to post-ET myelofibrosis. Genotyping for CALR mutations represents a novel useful tool for establishing a clonal myeloproliferative disorder in JAK2 and MPL wt patients with thrombocytosis and may have prognostic and therapeutic relevance.

Impact of mutational status on outcomes in myelofibrosis patients treated with ruxolitinib in the COMFORT-II study.

The JAK1/JAK2 inhibitor ruxolitinib produced significant reductions in splenomegaly and symptomatic burden and improved survival in patients with myelofibrosis (MF), irrespective of their JAK2 mutation status, in 2 phase III studies against placebo (COMFORT-I) and best available therapy (COMFORT-II). We performed a comprehensive mutation analysis to evaluate the impact of 14 MF-associated mutations on clinical outcomes in 166 patients included in COMFORT-II. We found that responses in splenomegaly and symptoms, as well as the risk of developing ruxolitinib-associated anemia and thrombocytopenia, occurred at similar frequencies across different mutation profiles. Ruxolitinib improved survival independent of mutation profile and reduced the risk of death in patients harboring a set of prognostically detrimental mutations (ASXL1, EZH2, SRSF2, IDH1/2) with an hazard ratio of 0.57 (95% confidence interval: 0.30-1.08) vs best available therapy. These data indicate that clinical efficacy and survival improvement may occur across different molecular subsets of patients with MF treated with ruxolitinib.

Impact of ruxolitinib on the natural history of primary myelofibrosis: a comparison of the DIPSS and the COMFORT-2 cohorts.

The international prognostic scoring system (IPSS) provides reliable risk assessment in patients with primary myelofibrosis (PMF). Recent clinical trials in PMF patients with intermediate-2 or high IPSS risk have shown a survival advantage of ruxolitinib over placebo (COMFORT-1) or best available therapy (COMFORT-2). Because crossover was allowed in these studies, we analyzed the cohort of ruxolitinib-naive patients used for developing the dynamic IPSS (DIPSS). By adopting ad hoc statistical analyses, we compared survival from diagnosis of 100 PMF patients receiving ruxolitinib within COMFORT-2 with that of 350 patients of the DIPSS study. Subjects were properly matched, and both left-truncation and right-censoring were accounted in order to compare higher IPSS risks exclusively. Patients receiving ruxolitinib had longer survival (5 years, 95% confidence interval [CI]: 2.9-7.8 vs 3.5 years, 95% CI: 3.0-3.9) with a hazard ratio of 0.61 (95% CI: 0.41-0.91; P = .0148). This observation suggests that ruxolitinib may modify the natural history of PMF.

Long-term survival and blast transformation in molecularly annotated essential thrombocythemia, polycythemia vera, and myelofibrosis.

Janus kinase 2 (JAK2) mutations define polycythemia vera (PV). Calreticulin (CALR) and myeloproliferative leukemia virus oncogene (MPL) mutations are specific to JAK2-unmutated essential thrombocythemia (ET) and primary myelofibrosis (PMF). We examined the effect of these mutations on long-term disease outcome. One thousand five hundred eighty-one patients from the Mayo Clinic (n = 826) and Italy (n = 755) were studied. Fifty-eight percent of Mayo patients were followed until death; median survivals were 19.8 years in ET (n = 292), 13.5 PV (n = 267; hazard ratio [HR], 1.8; 95% confidence interval [CI], 1.4-2.2), and 5.9 PMF (n = 267; HR, 4.5; 95% CI, 3.5-5.7). The survival advantage of ET over PV was not affected by JAK2/CALR/MPL mutational status. Survival in ET was inferior to the age- and sex-matched US population (P < .001). In PMF (n = 428), but not in ET (n = 576), survival and blast transformation (BT) were significantly affected by mutational status; outcome was best in CALR-mutated and worst in triple-negative patients: median survival, 16 vs 2.3 years (HR, 5.1; 95% CI, 3.2-8.0) and BT, 6.5% vs 25% (HR, 7.6; 95% CI, 2.8-20.2), respectively. We conclude that life expectancy in morphologically defined ET is significantly reduced but remains superior to that of PV, regardless of mutational status. In PMF, JAK2/CALR/MPL mutational status is prognostically informative.

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.

Epidemiology and clinical relevance of mutations in postpolycythemia vera and postessential thrombocythemia myelofibrosis: A study on 359 patients of the AGIMM group.

Transformation to secondary myelofibrosis (MF) occurs as part of the natural history of polycythemia vera (PPV-MF) and essential thrombocythemia (PET-MF). Although primary (PMF) and secondary MF are considered similar diseases and managed similarly, there are few studies specifically focused on the latter. The aim of this study was to characterize the mutation landscape, and describe the main clinical correlates and prognostic implications of mutations, in a series of 359 patients with PPV-MF and PET-MF. Compared with PV and ET, the JAK2V617F and CALR mutated allele burden was significantly higher in PPV-MF and/or PET-MF, indicating a role for accumulation of mutated alleles in the process of transformation to MF. However, neither the allele burden nor the type of driver mutation influenced overall survival (OS), while absence of any driver mutation (triple negativity) was associated with significant reduction of OS in PET-MF, similar to PMF. Of the five interrogated subclonal mutations (ASXL1, EZH2, SRSF2, IDH1, and IDH2), that comprise a prognostically detrimental high molecular risk (HMR) category in PMF, only SRSF2 mutations were associated with reduced survival in PET-MF, and no additional mutation profile with prognostic relevance was highlighted. Overall, these data indicate that the molecular landscape of secondary forms of MF is different from PMF, suggesting that unknown mutational events might contribute to the progression from chronic phase disease to myelofibrosis. These findings also support more extended genotyping approaches aimed at identifying novel molecular abnormalities with prognostic relevance for patients with PPV-MF and PET-MF. Am. J. Hematol. 91:681-686, 2016. © 2016 Wiley Periodicals, Inc.

Prognostic impact of bone marrow fibrosis in primary myelofibrosis. A study of the AGIMM group on 490 patients.

The prognostic significance of bone marrow (BM) fibrosis grade in patients with primary myelofibrosis (PMF) is still debated. A fibrosis grade greater than 1 was shown to associate with higher risk of death, and addition of fibrosis grade to IPSS score resulted in a more accurate prediction of survival. The aim of this study was to analyze the prognostic impact of BM fibrosis in 490 patients with PMF, evaluated at diagnosis, molecularly annotated and with extensive follow-up information. We found that fibrosis grade 2 and greater on a 0-3 scale was associated with clinical characteristics indicative of a more advanced disease, such as anemia, leukopenia, thrombocytopenia, constitutional symptoms, larger splenomegaly and a higher IPSS risk category. Patients with higher grade of fibrosis were also more likely to have additional somatic mutations in ASXL1 and EZH2, that are prognostically adverse. Median survival was significantly reduced in patients with grade 2 and 3 fibrosis as compared with grade 1; this effect was maintained when analysis was restricted to younger patients. In multivariate analysis, fibrosis grade independently predicted for survival regardless of IPSS variables and mutational status; the adverse impact of fibrosis was noticeable especially in lower IPSS risk categories. Overall, results indicate that higher grades of fibrosis correlate with unique clinical and molecular aspects and represent an independent adverse variable in patients with PMF; these observations deserve confirmation in prospectively designed series of patients. Am. J. Hematol. 91:918-922, 2016. © 2016 Wiley Periodicals, Inc.

Clinical presentation and management practice of systemic mastocytosis. A survey on 460 Italian patients.

Systemic mastocytosis is a rare heterogeneous myeloproliferative neoplasm characterized by abnormal proliferation and activation of mast cells. We describe a large multicentre series of 460 adult patients with systemic mastocytosis, with a diagnosis based on WHO 2008 criteria, in a "real-life" setting of ten Italian centers with dedicated multidisciplinary programs. We included indolent forms with (n = 255) and without (n = 165) skin lesions, smouldering (n = 20), aggressive (n = 28), associated with other hematological diseases mastocytosis (n = 21) and mast cell leukemia (n = 1). This series was uniquely characterized by a substantial proportion of patients with low burden of neoplastic mast cells; notably, 38% of cases were diagnosed using only minor diagnostic criteria according to WHO 2008 classification, underlying the feasibility of early diagnosis where all diagnostic approaches are made available. This has particular clinical relevance for prevention of anaphylaxis manifestations, that were typically associated with indolent forms. In multivariate analysis, the most important features associated with shortened overall survival were disease subtype and age at diagnosis >60 years. Disease progression was correlated with mastocytosis subtype and thrombocytopenia. As many as 32% of patients with aggressive mastocytosis suffered from early evolution into acute leukemia. Overall, this study provides novel information about diagnostic approaches and current presentation of patients with SM and underlines the importance of networks and specialized centers to facilitate early diagnosis and prevent disease-associated manifestations. Am. J. Hematol. 91:692-699, 2016. © 2016 Wiley Periodicals, Inc.

Tetraspanin CD9 participates in dysmegakaryopoiesis and stromal interactions in primary myelofibrosis.

Primary myelofibrosis is characterized by clonal myeloproliferation, dysmegakaryopoiesis, extramedullary hematopoiesis associated with myelofibrosis and altered stroma in the bone marrow and spleen. The expression of CD9, a tetraspanin known to participate in megakaryopoiesis, platelet formation, cell migration and interaction with stroma, is deregulated in patients with primary myelofibrosis and is correlated with stage of myelofibrosis. We investigated whether CD9 participates in the dysmegakaryopoiesis observed in patients and whether it is involved in the altered interplay between megakaryocytes and stromal cells. We found that CD9 expression was modulated during megakaryocyte differentiation in primary myelofibrosis and that cell surface CD9 engagement by antibody ligation improved the dysmegakaryopoiesis by restoring the balance of MAPK and PI3K signaling. When co-cultured on bone marrow mesenchymal stromal cells from patients, megakaryocytes from patients with primary myelofibrosis displayed modified behaviors in terms of adhesion, cell survival and proliferation as compared to megakaryocytes from healthy donors. These modifications were reversed after antibody ligation of cell surface CD9, suggesting the participation of CD9 in the abnormal interplay between primary myelofibrosis megakaryocytes and stroma. Furthermore, silencing of CD9 reduced CXCL12 and CXCR4 expression in primary myelofibrosis megakaryocytes as well as their CXCL12-dependent migration. Collectively, our results indicate that CD9 plays a role in the dysmegakaryopoiesis that occurs in primary myelofibrosis and affects interactions between megakaryocytes and bone marrow stromal cells. These results strengthen the "bad seed in bad soil" hypothesis that we have previously proposed, in which alterations of reciprocal interactions between hematopoietic and stromal cells participate in the pathogenesis of primary myelofibrosis.

Patterns of presentation and thrombosis outcome in patients with polycythemia vera strictly defined by WHO-criteria and stratified by calendar period of diagnosis.

Most studies in polycythemia vera (PV) include patients with both remote and most recent diagnostic periods and are therefore vulnerable to inaccurate interpretation of time-dependent data. We addressed the particular issue by analyzing presenting characteristics and outcome data among 1,545 patients with WHO-defined PV stratified by a diagnosis period of before or after 2005, which coincides with the first description of JAK2V617F as the molecular marker of PV. Patients diagnosed after 2005 displayed lower hemoglobin values (P < 0.0001) and older age (P = 0.007) at diagnosis; we suggest ease of diagnosis offered by a molecular marker enabled earlier diagnosis and broader application across older age groups that is further enhanced by recent trends in increased attention and health monitoring for the elderly. Post-2005 diagnosed patients were also more or less likely to receive aspirin and cytoreductive therapy, respectively, and, despite their older age distribution, displayed significantly lower risk of thrombosis in high risk disease. Regardless of the contributing factors to the latter phenomenon, our observations underscore the need to reassess current demographics and frequencies of thrombosis in clinical trial designs including thrombosis prevention in PV.

A phase 2 study of ruxolitinib, an oral JAK1 and JAK2 Inhibitor, in patients with advanced polycythemia vera who are refractory or intolerant to hydroxyurea.

BACKGROUND: Polycythemia vera (PV) is a myeloproliferative neoplasm associated with somatic gain-of-function mutations of Janus kinase-2 (JAK2). Therapeutic options are limited in patients with advanced disease. Ruxolitinib, an oral JAK1/JAK2 inhibitor, is active in preclinical models of PV. The long-term efficacy and safety of ruxolitinib in patients with advanced PV who are refractory or intolerant to hydroxyurea were studied in a phase 2 trial. METHODS: Response was assessed using modified European LeukemiaNet criteria, which included a reduction in hematocrit to <45% without phlebotomy, resolution of palpable splenomegaly, normalization of white blood cell and platelet counts, and reduction in PV-associated symptoms. RESULTS: Thirty-four patients received ruxolitinib for a median of 152 weeks (range, 31 weeks-177 weeks) or 35.0 months (range, 7.1 months-40.7 months). Hematocrit <45% without phlebotomy was achieved in 97% of patients by week 24.Only 1 patient required a phlebotomy after week 4. Among patients with palpable splenomegaly at baseline, 44% and 63%, respectively, achieved nonpalpable spleen measurements at weeks 24 and 144. Clinically meaningful improvements in pruritus, night sweats, and bone pain were observed within 4 weeks of the initiation of therapy and maintained with continued treatment. Ruxolitinib treatment also reduced elevated levels of inflammatory cytokines and granulocyte activation. Thrombocytopenia and anemia were the most common adverse events.Thrombocytopenia of grade 3 or anemia of grade 3 (according to National Cancer Institute Common Terminology Criteria for Adverse Events,version 3.0) occurred in 3 patients each (9%) (1 patient had both) and were managed with dose modification. CONCLUSIONS: Ruxolitinib was generally well tolerated and provided rapid and durable clinical benefits in patients with advanced PV who were refractory or intolerant to hydroxyurea.

A lower intensity of treatment may underlie the increased risk of thrombosis in young patients with masked polycythaemia vera.

In patients who do not meet the World Health Organization (WHO) criteria for overt polycythaemia vera (PV), a diagnosis of masked PV (mPV) can be determined. A fraction of mPV patients may display thrombocytosis, thus mimicking essential thrombocythaemia (ET). No previous studies have examined clinical outcomes of mPV among young JAK2-mutated patients. We analysed a retrospective cohort of 538 JAK2-mutated patients younger than 40 years, after a re-assessment of the diagnosis according to the haemoglobin threshold for mPV. In this cohort of patients, 97 (18%) met the WHO criteria for PV, 66 patients (12%) were classified as mPV and 375 (70%) as JAK2-mutated ET. Surprisingly, a significant difference in the incidence of thrombosis was found when comparing mPV versus overt PV patients (P = 0·04). In multivariate analysis, the only factor accounting for the difference in the risk of thrombosis was the less frequent use of phlebotomies and cytoreduction in mPV patients compared to those with overt PV. Thus, we emphasize the need for the identification of mPV in young JAK2-mutated patients in order to optimize their treatments.