JAK2V617F mutational status and allele burden have little influence on clinical phenotype and prognosis in patients with post-polycythemia vera and post-essential thrombocythemia myelofibrosis

Martin A, Wang Y, He M, Spellman SR, Wang T, Deeg HJ, Gupta V, Lee SJ, Bolon YT, Chanock SJ, Machiela MJ, Saber W, Gadalla SM. JAK2 V617F mutation and associated chromosomal alterations in primary and secondary myelofibrosis and post-HCT outcomes

JAK2 V617F is the most common driver mutation in primary or secondary myelofibrosis for which allogeneic hematopoietic cell transplantation (HCT) is the only curative treatment. Knowledge of the prognostic utility of JAK2 alterations in the HCT setting is limited. We identified all patients with MF who received HCT between 2000 and 2016 and had a pre-HCT blood sample (N = 973) available at the Center of International Blood and Marrow Transplant Research biorepository. PacBio sequencing and single nucleotide polymorphism-array genotyping were used to identify JAK2V617F mutation and associated mosaic chromosomal alterations (mCAs), respectively. Cox proportional hazard models were used for HCT outcome analyses. Genomic testing was complete for 924 patients with MF (634 primary MF [PMF], 135 postpolycythemia vera [PPV-MF], and 155 postessential thrombocytopenia [PET-MF]). JAK2V617F affected 562 patients (57.6% of PMF, 97% of PPV-MF, and 42.6% of PET-MF). Almost all patients with mCAs involving the JAK2 region (97.9%) were JAK2V617-positive. In PMF, JAK2V617F mutation status, allele burden, or identified mCAs were not associated with disease progression/relapse, nonrelapse mortality (NRM), or overall survival. Almost all PPV-MF were JAK2V617F-positive (97%), with no association between HCT outcomes and mutation allele burden or mCAs. In PET-MF, JAK2V617F high mutation allele burden (≥60%) was associated with excess risk of NRM, restricted to transplants received in the era of JAK inhibitors (2013-2016; hazard ratio = 7.65; 95% confidence interval = 2.10-27.82; P = .002). However, allele burden was not associated with post-HCT disease progression/relapse or survival. Our findings support the concept that HCT can mitigate the known negative effect of JAK2V617F in patients with MF, particularly for PMF and PPV-MF.

Association of Myelofibrosis Phenotypes with Clinical Manifestations, Molecular Profiles, and Treatments

Myelofibrosis (MF) presents an array of clinical manifestations and molecular profiles. The two distinct phenotypes- myeloproliferative and myelodepletive or cytopenic- are situated at the two poles of the disease spectrum and are largely defined by different degrees of cytopenias, splenomegaly, and distinct molecular profiles. The myeloproliferative phenotype is characterized by normal/higher peripheral blood counts or mildly decreased hemoglobin, progressive splenomegaly, and constitutional symptoms. The myeloproliferative phenotype is typically associated with secondary MF, higher JAK2 V617F burden, fewer mutations, and superior overall survival (OS). The myelodepletive phenotype is usually associated with primary MF, ≥2 cytopenias, modest splenomegaly, lower JAK2 V617F burden, higher fibrosis, greater genomic complexity, and inferior OS. Cytopenias are associated with mutations in epigenetic regulators/splicing factors, clonal evolution, disease progression, and shorter OS. Clinical variables, in conjunction with the molecular profiles, inform integrated prognostication and disease management. Ruxolitinib/fedratinib and pacritinib/momelotinib may be more suitable to treat patients with the myeloproliferative and myelodepletive phenotypes, respectively. Appreciation of MF heterogeneity and two distinct phenotypes, the different clinical manifestations and molecular profiles associated with each phenotype alongside the growing treatment expertise, the development of non-myelosuppressive JAK inhibitors, and integrated prognostication are leading to a new era in patient management. Physicians can increasingly tailor personalized treatments that will address the unique unmet needs of MF patients, including those presenting with the myelodepletive phenotype, to elicit optimal outcomes and extended OS across the disease spectrum.

How I treat polycythemia vera

Since its discovery, polycythemia vera (PV) has challenged clinicians responsible for its diagnosis and management and scientists investigating its pathogenesis. As a clonal hematopoietic stem cell (HSC) disorder, PV is a neoplasm but its driver mutations result in overproduction of morphologically and functionally normal blood cells. PV arises in an HSC but it can present initially as isolated erythrocytosis, leukocytosis, thrombocytosis, or any combination of these together with splenomegaly or myelofibrosis, and it can take years for a true panmyelopathy to appear. PV shares the same JAK2 mutation as essential thrombocytosis and primary myelofibrosis, but erythrocytosis only occurs in PV. However, unlike secondary causes of erythrocytosis, in PV, the plasma volume is frequently expanded, masking the erythrocytosis and making diagnosis difficult if this essential fact is ignored. PV is not a monolithic disorder: female patients deregulate fewer genes and clinically behave differently than their male counterparts, while some PV patients are genetically predisposed to an aggressive clinical course. Nevertheless, based on what we have learned over the past century, most PV patients can lead long and productive lives. In this review, using clinical examples, I describe how I diagnose and manage PV in an evidence-based manner without relying on chemotherapy.

Quantitation of JAK2 V617F Allele Burden by Using the QuantStudio™ 3D Digital PCR System

The JAK2 V617F mutation is highly prevalent in patients with myeloproliferative neoplasms (MPN). Furthermore, it has been shown that its allelic burden correlates with hematologic characteristics, drug response, and clinical endpoints in MPN patients. Digital PCR is an emerging technology for sensitive mutation detection and quantitation, based on dilution and high-grade partitioning of a sample. Here, we describe the use of the nanofluidic chip-based QuantStudio™ 3D Digital PCR System for quantitation of the JAK2 V617F mutation.

Prognostication in Philadelphia Chromosome Negative Myeloproliferative Neoplasms: a Review of the Recent Literature

PURPOSE OF REVIEW

The prognosis for patients with Philadelphia chromosome (Ph)-negative myeloproliferative neoplasms (MPNs) is highly variable. All Ph-negative MPNs carry an increased risk for thrombotic complications, bleeding, and leukemic transformation. Several clinical, biological, and molecular prognostic factors have been identified in recent years, which provide important information in guiding management of patients with Ph-negative MPNs. In this review, we critically evaluate the recent published literature and discuss important new developments in clinical and molecular factors that impact survival, disease transformation, and thrombosis in patients with polycythemia vera, essential thrombocythemia, and primary myelofibrosis.

RECENT FINDINGS

Recent studies have identified several clinical factors and non-driver mutations to have prognostic impact on Ph-negative MPNs independent of conventional risk stratification and prognostic models. In polycythemia vera (PV), leukocytosis, abnormal karyotype, phlebotomy requirement on hydroxyurea, increased bone marrow fibrosis, and mutations in ASXL1, SRSF2, and IDH2 were identified as additional adverse prognostic factors. In essential thrombocythemia (ET), JAK2 V617F mutation, splenomegaly, and mutations in SH2B3, SF3B1, U2AF1, TP53, IDH2, and EZH2 were found to be additional negative prognostic factors. Bone marrow fibrosis and mutations in ASXL1, SRSF2, EZH2, and IDH1/2 have been found to be additional prognostic factors in primary myelofibrosis (PMF). CALR mutations appear to be a favorable prognostic factor in PMF, which has not been clearly demonstrated in ET. The prognosis for patients with PV, ET, and PMF is dependent upon the presence or absence of several clinical, biological, and molecular risk factors. The significance of additional risk factors identified in these recent studies will need further validation in prospective studies to determine how they may be best utilized in the management of these disorders.

Patients with post-essential thrombocythemia and post-polycythemia vera differ from patients with primary myelofibrosis

Prognostic scoring systems for primary myelofibrosis (PMF) are not accurate in patients with post-essential thrombocythemia and post-polycythemia vera myelofibrosis (PET-MF; PPV-MF). Given the paucity of data describing the clinical characteristics, disease course and outcomes of these patients, we sought to describe and compare the clinical characteristics and outcomes of 755 patients with PMF, 181 with PPV-MF, and 163 with PET-MF referred to our institution between 1984 and 2013. The median follow-up was 31 months, and 56% (n=616) patients had died. Over an observation period of 3502 person-years, 11% of patients had progression to AML, with similar rates among groups. The proportion of patients with transfusion dependency (higher in PMF), leukocytosis and systemic symptoms (higher in PPV-MF), and thrombocytopenia (higher in PMF, PPV-MF) differed among groups. Median overall survival (OS) was longest in PET-MF patients (73 mo vs 45 mo (PMF) vs 48 mo (PPV-MF), p <0.001). Stratification of OS by DIPSS was only discriminatory in patients with PMF, and it failed to distinguish higher risk patients with PPV/PET-MF. In multivariate analysis, predictors of inferior OS were higher age, anemia, systemic symptoms, thrombocytopenia, and high peripheral blasts in PMF; age, anemia, and systemic symptoms for PPV-MF; and anemia, peripheral blasts and thrombocytopenia in PET-MF. Although the clinical characteristics of PPV/PET-MF patients are not substantially different from those with PMF, their outcomes differ and prognostic scoring systems for PET/PPV-MF should be improved.

Detection of driver and subclonal mutations in myelofibrosis: clinical impact on pharmacologic and transplant based treatment strategies

INTRODUCTION

Myelofibrosis (MF) is the most aggressive form among Philadelphia negative (Ph-) myeloproliferative neoplasms (MPNs). In the last years, the mutational landscape of MF has expanded remarkably by the identification of additional recurrent mutations, called subclonal mutations. Areas covered: Here we describe the available data about the currently identified subclonal mutations and their prognostic value in MF patients. We also review the practical value of including such molecular information in available prognostic models for both outcome prediction and possibly treatment decision with regards to transplant indication. Lastly, we covered the available data on the application of molecular markers for minimal residual disease (MRD) monitoring after transplantation. Expert commentary: The demonstration of the prognostic value of additional mutations suggests to define this molecular profile at diagnosis and when an allogeneic transplant can be advised, particularly in younger patients. The presence of molecular markers might offer the possibility to evaluate the depth of remission and to monitor MRD after transplantation. Prospective clinical studies are needed to validate the use of this molecular data in the routine clinical practice.

The evolution and clinical relevance of prognostic classification systems in myelofibrosis

Primary myelofibrosis, the most aggressive of the classic Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), is a clonal disorder characterized by often debilitating constitutional symptoms and splenomegaly, bone marrow fibrosis and resultant cytopenias, extramedullary hematopoiesis, risk of leukemic transformation, and shortened survival. Post-polycythemia vera and post-essential thrombocythemia myelofibrosis represent similar entities, although some differences are being recognized. Attempts to classify patients with myelofibrosis into prognostic categories have been made since the late 1980s, and these scoring systems continue to evolve as new information becomes available. Over the last decade, the molecular pathogenesis of MPNs has been elucidated considerably, and the Janus kinase (JAK) 1/2 inhibitor ruxolitinib is the first drug specifically approved by the US Food and Drug Administration to treat patients with intermediate-risk and high-risk myelofibrosis. This article reviews the evolution of prognostic criteria in myelofibrosis, emphasizing the major systems widely in use today, as well as recently described, novel systems that incorporate emerging data regarding somatic mutations. Risk factors for thrombosis and conversion to MPN blast phase also are discussed. Finally, the practical usefulness of the current prognostic classification systems in terms of clinical decision making is discussed, particularly within the context of some of their inherent weaknesses. Cancer 2016;122:681-692. © 2015 American Cancer Society.

Guidelines for the management of myeloproliferative neoplasms

Polycythemia vera, essential thrombocythemia, and primary myelofibrosis are collectively known as 'Philadelphia-negative classical myeloproliferative neoplasms (MPNs).' The discovery of new genetic aberrations such as Janus kinase 2 (JAK2) have enhanced our understanding of the pathophysiology of MPNs. Currently, the JAK2 mutation is not only a standard criterion for diagnosis but is also a new target for drug development. The JAK1/2 inhibitor, ruxolitinib, was the first JAK inhibitor approved for patients with intermediate- to high-risk myelofibrosis and its effects in improving symptoms and survival benefits were demonstrated by randomized controlled trials. In 2011, the Korean Society of Hematology MPN Working Party devised diagnostic and therapeutic guidelines for Korean MPN patients. Subsequently, other genetic mutations have been discovered and many kinds of new drugs are now under clinical investigation. In view of recent developments, we have revised the guidelines for the diagnosis and management of MPN based on published evidence and the experiences of the expert panel. Here we describe the epidemiology, new genetic mutations, and novel therapeutic options as well as diagnostic criteria and standard treatment strategies for MPN patients in Korea.

Molecular diagnostics of myeloproliferative neoplasms

Since the discovery of the JAK2 V617F mutation in the majority of the myeloproliferative neoplasms (MPN) of polycythemia vera, essential thrombocythemia and primary myelofibrosis ten years ago, further MPN-specific mutational events, notably in JAK2 exon 12, MPL exon 10 and CALR exon 9 have been identified. These discoveries have been rapidly incorporated into evolving molecular diagnostic algorithms. Whilst many of these mutations appear to have prognostic implications, establishing MPN diagnosis is of immediate clinical importance with selection, implementation and the continual evaluation of the appropriate laboratory methodology to achieve this diagnosis similarly vital. The advantages and limitations of these approaches in identifying and quantitating the common MPN-associated mutations are considered herein with particular regard to their clinical utility. The evolution of molecular diagnostic applications and platforms has occurred in parallel with the discovery of MPN-associated mutations, and it therefore appears likely that emerging technologies such as next-generation sequencing and digital PCR will in the future play an increasing role in the molecular diagnosis of MPN.

The Burden of JAK2V617F Mutated Allele in Turkish Patients With Myeloproliferative Neoplasms

BACKGROUND

Studies regarding the impact of JAK2V617F allele burden on phenotypic properties and clinical course in Philadelphia-negative myeloproliferative neoplasms (Ph-negative MPNs) have reported variable results. We aimed to analyze the association of mutated JAK2V617F allele burden with laboratory characteristics and clinical phenotype in Turkish patients (107 essential thrombocythemia (ET) and 77 primary myelofibrosis (PMF)).

METHODS

Peripheral blood samples of 184 patients with Ph-negative MPNs were analyzed for JAK2V617F allele status and burden. JAK2 MutaScreen assay (Ipsogen, Luminy Biotech, Marseille, France) was used to detect the JAK2V617F status and quantitative JAK2V617F allele burdens in genomic DNA using TaqMan allelic discrimination.

RESULTS

Frequency of JAK2V617F-positive patients with high mutation load (allele burden > 50%) was higher in PMF compared to ET (23.4% and 4.7%, respectively; P = 0.001). We found significant association between ET patients with high JAK2V617F allele burden and lower hemoglobin (Hgb) and hematocrit (Hct), higher LDH levels and more prevalent massive splenomegaly (P = 0.001, P = 0.001, P = 0.012 and P = 0.015, respectively). ET patients with high mutation load displayed higher prevalence of bleeding compared to low mutation load and wild-type mutational status (P = 0.003). Rate of DVT was significantly higher in ET patients with mutant allele burden in upper half compared to lower half and wild-type (P = 0.029). We observed significant association between PMF patients with high JAK2V617F allele burden and higher Hgb, Hct levels and leukocyte counts (P = 0.003, P = 0.021 and P = 0.001, respectively).

CONCLUSIONS

Our study demonstrated JAK2V617F allele burden correlates with clinical features in ET and PMF. We conclude quantification of JAK2V617F mutation contributes to the workup of Ph-negative MPNs.

Prognostication in MF: from CBC to cytogenetics to molecular markers

Myelofibrosis (MF) is a clonal stem cell disorder characterized by ineffective erythropoiesis and extramedullary hematopoiesis leading to progressive bone marrow failure, severe anemia, constitutional symptoms, hepatosplenomegaly, and thrombosis. MF can arise following a history of polycythemia vera (PV) or essential thrombocythemia (ET), or can present de novo as primary myelofibrosis (PMF). The disease course is variable with median survival ranging from months to years. Clinical and biological features such as advanced age, leukocytosis, anemia, transfusion dependence, and elevated inflammatory markers can impact prognosis in patients with PMF. Cytogenetic abnormalities and molecular markers such as JAK2 V617F, ASXL1, and CALR mutations have also been identified as prognostic variables. Several different scoring systems have been developed based on these prognostic factors. In this review, we will discuss the clinical, biological, molecular, and cytogenetic prognostic factors that have been identified in PMF, and the current prognostic models that have been developed to guide treatment decisions.

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.

A rare der(Y)t(Y;1)(q12;q12) in a patient with post-polycythemic myelofibrosis: a case report

We describe a case of post-polycythemic myelofibrosis harboring der(Y)t(Y;1)(q12;q12). The patient was a 69-year-old man and was initially diagnosed with polycythemia vera. During the clinical course of his condition, the polycythemia developed into myelofibrosis. Chromosome analysis detected der(Y)t(Y;1)(q12;q12). We discuss the association between der(Y)t(Y;1)(q11~12;q12~21) and tumorigenesis along with a review of literature.

JAK2 Allele Burden in the Myeloproliferative Neoplasms: Effects on Phenotype, Prognosis and Change with Treatment

The field of Philadelphia-chromosome-negative chronic myeloproliferative neoplasms (MPNs) has recently witnessed tremendous advances in the basic knowledge of disease pathophysiology that followed the identification of mutations in JAK2 and MPL. These discoveries led to a revision of the criteria employed for diagnosis by the World Health Organization. The prognostic role of the JAK2V617F mutation and of its allelic burden has been the objective of intensive research using a variety of cellular and animal models as well as in large series of patients. While a definitive position cannot yet been taken on all of the issues, there is a consensus that the presence of higher V617F allele burden, that is on the basis of a stronger activation of intracellular signalling pathways, is associated with the clinical phenotype of polycythemia vera and with defined haematological and clinical markers indicative of a more aggressive phenotype. On the other hand, a low allele burden in myelofibrosis is associated with reduced survival. Finally, a significant reduction of JAK2 V617F allele burden has been demonstrated in patients treated with interferon, while the effects of novel JAK1 and JAK2 inhibitors have not yet been fully ascertained.

EZH2 mutational status predicts poor survival in myelofibrosis

We genotyped 370 subjects with primary myelofibrosis (PMF) and 148 with postpolycythemia vera/postessential thrombocythemia (PPV/PET) MF for mutations of EZH2. Mutational status at diagnosis was correlated with hematologic parameters, clinical manifestations, and outcome. A total of 25 different EZH2 mutations were detected in 5.9% of PMF, 1.2% of PPV-MF, and 9.4% of PET-MF patients; most were exonic heterozygous missense changes. EZH2 mutation coexisted with JAK2V617F or ASXL1 mutation in 12 of 29 (41.4%) and 6 of 27 (22.2%) evaluated patients; TET2 and CBL mutations were found in 2 and 1 patients, respectively. EZH2-mutated PMF patients had significantly higher leukocyte counts, blast-cell counts, and larger spleens at diagnosis, and most of them (52.6%) were in the high-risk International Prognostic Score System (IPSS) category. After a median follow-up of 39 months, 128 patients (25.9%) died, 81 (63.3%) because of leukemia. Leukemia-free survival (LFS) and overall survival (OS) were significantly reduced in EZH2-mutated PMF patients (P = .028 and P < .001, respectively); no such impact was seen for PPV/PET-MF patients, possibly due to the low number of mutated cases. In multivariate analysis, survival of PMF patients was predicted by IPSS high-risk category, a < 25% JAK2V617F allele burden, and EZH2 mutation status. We conclude that EZH2 mutations are independently associated with shorter survival in patients with PMF.

Association of JAK2 mutation status and cytogenetic abnormalities in myeloproliferative neoplasms and myelodysplastic/myeloproliferative neoplasms

Myeloproliferative neoplasms and myelodysplastic/myeloproliferative neoplasms are heterogeneous disorders. JAK2 mutation testing and karyotyping are routinely used for diagnosis but have not been incorporated into risk stratification in Philadelphia chromosome-negative myeloproliferative neoplasms. This study correlated cytogenetic abnormalities with disease stage and JAK2 status. A total of 179 cases were analyzed for the JAK2 mutation. Among them, cytogenetic data were available for 97 cases-45 of 106 JAK2+ and 52 of 73 JAK2-. The JAK2+ group showed a higher frequency of cytogenetic anomalies than the JAK2- group (23/45 [51%] vs 14/52 [27%]). Chromosome 9, chromosome 7, and 20q- were recurrent abnormalities in the JAK2+ group, whereas 13q- and trisomy 21 were common in the JAK2- group. In the JAK2+ group, chromosome 7 and complex cytogenetic abnormalities were associated with excess blasts/blastic transformation (P < .05), whereas no cases with 20q- underwent blastic transformation. Our results suggest that incorporation of JAK2 mutation testing and karyotyping allows for monitoring of disease progression with prognostic and therapeutic implications.

Prognostic factors and models in polycythemia vera, essential thrombocythemia, and primary myelofibrosis

Myeloproliferative neoplasms include essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF). These 3 diseases have common clinical features, such as a high risk of vascular complications, progression to secondary myelofibrosis, and clonal evolution into the blast phase. Current risk factors of ET and PV, used to predict events, are patient based: age >60 years and a history of thrombosis. Very recently, other parameters, such as leukocyte count and the presence of JAK2 (V617F) mutation, have been reported as potential risk factors. Prognosis in PMF is predicted at diagnosis by a combination of different risk factors, such as advanced age (age >60 years), anemia, leukocytosis (white blood cell count > 25 × 10(9)/L), the presence of blast cells (≥ 1%), and the presence of constitutional symptoms. This model may also predict survival when applied during follow-up.

Mutational analysis in BCR-ABL-negative classic myeloproliferative neoplasms: impact on prognosis and therapeutic choices

The diagnostic value of JAK2 mutational analysis in myeloproliferative neoplasms (MPN) is now well established and endorsed by the World Health Organization classification system for hematologic malignancies. The current review is focused on the prognostic impact and therapeutic relevance of JAK2 and other MPN-associated mutations in polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Mutations involving JAK2, MPL, TET2, and ASXL1 are discussed. In general, within a specific disease category, the mere presence or absence of any one of these mutations does not appear to correlate with survival or development of blast phase disease, myelofibrosis, or thrombosis. In contrast, interesting associations between JAK2V617F allele burden and clinical outcome (e.g. lower quartile range allele burden and shorter survival in PMF and higher allele burden and fibrotic transformation in PV) have been made, but require further validation, and their impact on treatment choices is not clear. Similarly, although detection of JAK2V617F status post allogeneic hematopoietic cell transplant indicates minimal residual disease, the general use of mutant allele burden for monitoring treatment response has not been systematically studied. Current information on mutational status and response to JAK2 inhibitor drug therapy is too preliminary to draw any conclusions.

A pilot study of the Histone-Deacetylase inhibitor Givinostat in patients with JAK2V617F positive chronic myeloproliferative neoplasms

A phase II A study was conducted to evaluate the safety and efficacy of Givinostat, a novel Histone-Deacetylases inhibitor, in patients with Polycythaemia Vera (PV, n = 12), Essential Thrombocythaemia (ET, n = 1) and Myelofibrosis (n = 16), bearing the JAK2V617F mutation. The study was approved by the local ethics committees and all human participants gave written informed consent. Givinostat was given orally for 24 weeks at a starting dose of 50 mg twice daily. The median treatment duration was 20 weeks. Reasons for treatment discontinuation were disease progression (n = 6), grade 2 thrombocytopenia (n = 1), psychiatric symptoms (n = 1) and withdrawn consent (n = 2). A dose reduction was applied in 10 patients while a temporary interruption occurred in 15. Among 13 PV/ET patients, 1 complete, 6 partial and 4 no responses were documented at study end while 2 patients went off-study, prematurely. Three major responses were registered among 16 MF patients. Pruritus disappeared in most patients and reduction of splenomegaly was observed in 75% of PV/ET and 38% of MF patients. Reverse transcription polymerase chain reaction identified a trend to reduction of the JAK2V617F allele burden. Givinostat was well tolerated and could induce haematological response in most PV and some MF patients.

Impact of JAK2V617F mutation status, allele burden, and clearance after allogeneic stem cell transplantation for myelofibrosis

Allogeneic stem cell transplantation (ASCT) after reduced-intensity conditioning has become a reasonable treatment option for patients with advanced myelofibrosis. The role of characteristic molecular genetic abnormalities, such as JAK2V617F on outcome of ASCT, is not yet elucidated. In 139 of 162 myelofibrosis patients with known JAK2V617F mutation status who received ASCT after reduced-intensity conditioning, the impact of JAK2 genotype, JAK2V617F allele burden, and clearance of mutation after ASCT was evaluated. Overall survival was significantly reduced in multivariate analysis in patients harboring JAK2 wild-type (hazard ratio = 2.14, P = .01) compared with JAK2 mutated patients. No significant influence on outcome was noted for the mutated allele burden analyzed either as continuous variable or after dividing into quartiles. Achievement of JAK2V617F negativity after ASCT was significantly associated with a decreased incidence of relapse (hazard ratio = 0.22, P = .04). In a landmark analysis, patients who cleared JAK2 mutation level in peripheral blood 6 months after ASCT had a significant lower risk of relapse (5% vs 35%, P = .03). We conclude that JAK2V617F-mutated status, but not allele frequency, resulted in an improved survival and rapid clearance after allografting reduces the risk of relapse.