Impact of Molecular Genetics on Outcome in Myelofibrosis Patients after Allogeneic Stem Cell Transplantation

Myelofibrosis and allogeneic transplantation: critical points and challenges

New available drugs allow better control of systemic symptoms associated with myelofibrosis (MF) and splenomegaly but they do not modify the natural history of progressive and poor prognosis disease. Thus, hematopoietic stem cell transplantation (HSCT) is still considered the only available curative treatment for patients with MF. Despite the increasing number of procedures worldwide in recent years, HSCT for MF patients remains challenging. An increasingly complex network of the patient, disease, and transplant-related factors should be considered to understand the need for and the benefits of the procedure. Unfortunately, prospective trials are often lacking in this setting, making an evidence-based decision process particularly arduous. In the present review, we will analyze the main controversial points of allogeneic transplantation in MF, that is, the development of more sophisticated models for the identification of eligible patients; the need for tools offering a more precise definition of expected outcomes combining comorbidity assessment and factors related to the procedure; the decision-making process about the best transplantation time; the evaluation of the most appropriate platform for curative treatment; the impact of splenomegaly; and splenectomy on outcomes.

Graft-versus-host disease and impact on relapse in myelofibrosis undergoing hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (alloHSCT) remains the only curative treatment for myelofibrosis (MF). Relapse occurs in 10-30% and remains a major factor for dismal outcomes. Previous work suggested that graft-versus-host disease (GVHD) might be associated with risk of relapse. This study included 341 patients undergoing their first (n = 308) or second (n = 33) alloHSCT. Anti-T-lymphocyte or antithymocyte globulin was used for GVHD prophylaxis in almost all patients. Median time to neutrophile and platelet engraftment was 13 days and 19 days, respectively. The cumulative incidence of acute GVHD grade II-IV was 41% (median, 31 days; range, 7-112). Grade III-IV acute GVHD was observed in 22%. The cumulative incidence of chronic GVHD was 61%. Liver was affected in 23% of acute GVHD cases and 46% of chronic GVHD cases. Severe acute GVHD was associated with high non-relapse mortality. The development of acute GVHD grade II and moderate GVHD was an independent factor for reduced risk for relapse after transplantation without increased risk for non-relapse mortality, while especially acute GVHD grade IV was associated with high non-relapse mortality. Last, we identified that ongoing response to ruxolitinib, accelerated-phase MF at time of transplantation and splenectomy prior to transplantation were independent predictors for relapse.

Laboratory methods of monitoring disease response after allogeneic haematopoietic stem cell transplantation for myelofibrosis

The era of molecular prognostication in myelofibrosis has allowed comprehensive assessment of disease risk and informed decisions regarding allogeneic haematopoietic stem cell transplantation (HSCT). However, monitoring disease response after transplantation is difficult, and limited by disease and sample-related factors. The emergence of laboratory techniques sensitive enough to monitor measurable residual disease is promising in predicting molecular and haematological relapse and guiding management. This paper summarises the existing literature regarding methods for detecting and monitoring disease response after HSCT in myelofibrosis and explores the therapeutic use of measurable residual disease (MRD) assays in transplant recipients. Laboratory assessment of disease response in myelofibrosis post-allogeneic transplant is limited by disease and treatment characteristics and by the sensitivity of available conventional molecular assays. The identification of MRD has prognostic implications and may allow early intervention to prevent relapse. Further applicability is limited by mutation-specific assay variability, a lack of standardisation and sample considerations.

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.

Allogeneic hematopoietic cell transplantation in patients with CALR-mutated myelofibrosis: a study of the Chronic Malignancies Working Party of EBMT

Allogeneic hematopoietic cell transplantation (allo-HCT) is curative for myelofibrosis (MF) but assessing risk-benefit in individual patients is challenging. This complexity is amplified in CALR-mutated MF patients, as they live longer with conventional treatments compared to other molecular subtypes. We analyzed outcomes of 346 CALR-mutated MF patients who underwent allo-HCT in 123 EBMT centers between 2005 and 2019. After a median follow-up of 40 months, the estimated overall survival (OS) rates at 1, 3, and 5 years were 81%, 71%, and 63%, respectively. Patients receiving busulfan-containing regimens achieved a 5-year OS rate of 71%. Non-relapse mortality (NRM) at 1, 3, and 5 years was 16%, 22%, and 26%, respectively, while the incidence of relapse/progression was 11%, 15%, and 17%, respectively. Multivariate analysis showed that older age correlated with worse OS, while primary MF and HLA mismatched transplants had a near-to-significant trend to decreased OS. Comparative analysis between CALR- and JAK2-mutated MF patients adjusting for confounding factors revealed better OS, lower NRM, lower relapse, and improved graft-versus-host disease-free and relapse-free survival (GRFS) in CALR-mutated patients. These findings confirm the improved prognosis associated with CALR mutation in allo-HCT and support molecular profiling in prognostic scoring systems to predict OS after transplantation in MF.

How I treat transplant-eligible patients with myelofibrosis

Despite the approval of Janus kinase inhibitors and novel agents for patients with myelofibrosis (MF), disease-modifying responses remain limited, and hematopoietic stem cell transplantation (HSCT) remains the only potentially curative treatment option. The number of HSCTs for MF continues to increase worldwide, but its inherent therapy-related morbidity and mortality limit its use for many patients. Furthermore, patients with MF often present at an older age, with cytopenia, splenomegaly, and severe bone marrow fibrosis, posing challenges in managing them throughout the HSCT procedure. Although implementation of molecular analyses enabled improved understanding of disease mechanisms and subsequently sparked development of novel drugs with promising activity, prospective trials in the HSCT setting are often lacking, making an evidence-based decision process particularly difficult. To illustrate how we approach patients with MF with respect to HSCT, we present 3 different clinical scenarios to capture relevant aspects that influence our decision making regarding indication for, or against, HSCT. We describe how we perform HSCT according to different risk categories and, furthermore, discuss our up-to-date approach to reduce transplant-related complications. Last, we show how to harness graft-versus-MF effects, particularly in the posttransplant period to achieve the best possible outcomes for patients.

The pharmacotherapeutic management of patients with myelofibrosis: looking beyond JAK inhibitors

INTRODUCTION

The approach to myelofibrosis (MF) has been revolutionized in recent years, overcoming the traditional therapies, often not very effective. Janus kinase inhibitors (JAKi - from ruxolitinib up to momelotinib) were the first class of drugs with considerable results.

AREAS COVERED

Ongoing, new molecules are being tested that promise to give hope even to those patients not eligible for bone marrow transplants who become intolerant or are refractory to JAKi, for which therapeutic hopes are currently limited. Telomerase, murine double minute 2 (MDM2), phosphatidylinositol 3-kinase δ (PI3Kδ), BCL-2/xL, and bromodomain and extra-terminal motif (BET) inhibitors are the drugs with promising results in clinical trials and close to closure with consequent placing on the market, finally allowing JAK to look beyond. The novelty of the MF field was searched in the PubMed database, and the recently completed/ongoing trials are extrapolated from the ClinicalTrial website.

EXPERT OPINION

From this point of view, the use of new molecules widely described in this review, probably in association with JAKi, will represent the future treatment of choice in MF, leaving, in any case, the potential new approaches actually in an early stage of development, such as the use of immunotherapy in targeting CALR, which is coming soon.

A simple prognostic system in patients with myelofibrosis undergoing allogeneic stem cell transplantation: a CIBMTR/EBMT analysis

To develop a prognostic model for patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT) for myelofibrosis (MF), we examined the data of 623 patients undergoing allo-HCT between 2000 and 2016 in the United States (the Center for International Blood and Marrow Transplant Research [CIBMTR] cohort). A Cox multivariable model was used to identify factors prognostic of mortality. A weighted score using these factors was assigned to patients who received transplantation in Europe (the European Bone Marrow Transplant [EBMT] cohort; n = 623). Patient age >50 years (hazard ratio [HR], 1.39; 95% confidence interval [CI], 0.98-1.96), and HLA-matched unrelated donor (HR, 1.29; 95% CI, 0.98-1.7) were associated with an increased hazard of death and were assigned 1 point. Hemoglobin levels <100 g/L at time of transplantation (HR, 1.63; 95% CI, 1.2-2.19) and a mismatched unrelated donor (HR, 1.78; 95% CI, 1.25-2.52) were assigned 2 points. The 3-year overall survival (OS) in patients with a low (1-2 points), intermediate (3-4 points), and high score (5 points) were 69% (95% CI, 61-76), 51% (95% CI, 46-56.4), and 34% (95% CI, 21-49), respectively (P < .001). Increasing score was predictive of increased transplant-related mortality (TRM; P = .0017) but not of relapse (P = .12). The derived score was predictive of OS (P < .001) and TRM (P = .002) but not of relapse (P = .17) in the EBMT cohort as well. The proposed system was prognostic of survival in 2 large cohorts, CIBMTR and EBMT, and can easily be applied by clinicians consulting patients with MF about the transplantation outcomes.

Donor Lymphocyte Infusion and Molecular Monitoring for Relapsed Myelofibrosis After Hematopoietic Cell Transplantation

Hematopoietic cell transplantation (HCT) is a curative approach for myelofibrosis patients, but relapse is a major cause of treatment failure. We investigated the effect of donor lymphocyte infusion (DLI) in 37 patients with molecular (n = 17) or hematological relapse (n = 20) after HCT. Patients received median of 2 (range, 1-5) cumulative DLI (total of 91 infusions). Median starting dose was 1 × 10⁶ cells/kg, escalated by half-log ≥6 weeks if no response nor graft-versus-host disease (GvHD) occurred. Median time to first DLI was 40 weeks for molecular relapse versus 145 weeks for hematological relapse. Overall molecular complete response (mCR) at any time was 73% (n = 27) and was significantly higher for initial molecular relapse (88%) versus hematological relapse (60%; P = 0.05). The 6-year overall survival was 77% versus 32% (P = 0.03). Acute GvHD 2-4 occurred in 22% and half of the patients achieved mCR without any GvHD. All patients who relapsed from mCR achieved after first DLI could be salvaged with subsequent DLI, showing long-term survival. No second HCT was needed for molecular relapse versus 6 for hematological relapse. This comprehensive and largest study to date suggests molecular monitoring together with DLI as standard of care and a crucial approach to achieve excellent outcomes in relapsed myelofibrosis.

Molecular diagnostic criteria of myeloproliferative neoplasms

INTRODUCTION

Myeloproliferative neoplasms (MPN) are a heterogeneous group of clonal hematopoietic stem cell neoplasms characterized by the driver mutations JAK2, CALR, and MPL. These mutations cause constitutive activation of JAK-STAT signaling, which is central to pathogenesis of MPNs. Next-generation sequencing has further expanded the molecular landscape allowing for improved diagnostics, prognostication, and targeted therapy.

AREAS COVERED

This review aims to address current understanding of the molecular diagnosis of MPN not only through improved awareness of the driver mutations but also the disease modifying mutations. In addition, other genetic factors such as clonal hematopoiesis of indeterminate potential (CHIP), order of mutation, and mutation co-occurrence are discussed and how these factors influence disease initiation and ultimately progression. How this molecular information is incorporated into risk stratification models allowing for earlier intervention and targeted therapy in the future will be addressed further.

EXPERT OPINION

The genomic landscape of the MPN has evolved in the last 15 years with integration of next-generation sequencing becoming the gold standard of MPN management. Although diagnostics and prognostication have become more personalized, additional studies are required to translate these molecular findings into targeted therapy therefore improving patient outcomes.

Impact of Molecular Biology in Diagnosis, Prognosis, and Therapeutic Management of BCR::ABL1-Negative Myeloproliferative Neoplasm

BCR::ABL1-negative myeloproliferative neoplasms (MPNs) include three major subgroups-polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF)-which are characterized by aberrant hematopoietic proliferation with an increased risk of leukemic transformation. Besides the driver mutations, which are JAK2, CALR, and MPL, more than twenty additional mutations have been identified through the use of next-generation sequencing (NGS), which can be involved with pathways that regulate epigenetic modifications, RNA splicing, or DNA repair. The aim of this short review is to highlight the impact of molecular biology on the diagnosis, prognosis, and therapeutic management of patients with PV, ET, and PMF.

Molecular Pathogenesis of Myeloproliferative Neoplasms

PURPOSE OF REVIEW

Myeloproliferative neoplasms (MPNs) are chronic hematological malignancies characterized by increased proliferation of MPN stem and myeloid progenitor cells with or without bone marrow fibrosis that typically lead to increased peripheral blood cell counts. The genetic and cytogenetic alterations that initiate and drive the development of MPNs have largely been defined, and we summarize these here.

RECENT FINDINGS

In recent years, advances in understanding the pathogenesis of MPNs have defined a long-preclinical phase in JAK2-mutant MPN, identified genetic loci associated with MPN predisposition and uncovered mechanistic insights in CALR-mutant MPN. The integration of molecular genetics into prognostic risk models is well-established in myelofibrosis and ongoing studies are interrogating the prognostic implications of concomitant mutations in ET and PV. Despite all these advances, the field is deficient in clonally selective therapies to effectively target the MPN clone at any stage of disease, from pre-clinical to advanced. Although the biological understanding of the pathogenesis of MPNs has progressed quickly, substantial knowledge gaps remain, including in the molecular mechanisms underlying MPN progression and myelofibrotic transformation. An ongoing goal for the MPN field is to translate advances in biological understanding to improved treatments for patients.

Innovative strategies to improve hematopoietic stem cell transplant outcomes in myelofibrosis

Myelofibrosis (MF) is a clonal myeloproliferative neoplasm characterized by inflammation, marrow fibrosis, and an inherent risk of blastic transformation. Hematopoietic allogeneic stem cell transplant is the only potentially curative therapy for this disease, however, survival gains observed for other transplant indications over the past two decades have not been realized for MF. The role of transplantation may also evolve with the use of novel targeted agents. The chronic inflammatory state associated with MF necessitates pretransplantation assessment of end-organ function. Applying the transplant methodology employed for other myeloid disorders to patients with MF fails to acknowledge differences in the underlying disease pathophysiology. Limited understanding of the causes of poor transplant outcomes in this cohort has prevented refinement of transplant eligibility criteria in MF. There is increasing evidence of heterogeneity in molecular disease grade, beyond the clinical manifestations which have traditionally guided transplant timing. Exploring the physiological consequences of disease chronicity unique to MF, acknowledging the heterogeneity in disease grade, and using advanced prognostic models, molecular diagnostics and other organ function diagnostic tools, we present an innovative review of strategies with the potential to improve transplant outcomes in this disease. Larger, prospective studies which consider the impact of molecular-based disease grade are needed for MF transplantation.

High Molecular and Cytogenetic Risk in Myelofibrosis Does Not Benefit From Higher Intensity Conditioning Before Hematopoietic Cell Transplantation: An International Collaborative Analysis

There is no direct evidence to recommend specific conditioning intensities in myelofibrosis undergoing allogeneic hematopoietic cell transplantation, especially in the molecular era. We aimed to compare outcomes of reduced intensity (RIC) or myeloablative conditioning (MAC) transplantation in myelofibrosis with molecular information. The study included 645 genetically annotated patients (with at least driver mutation status available), of whom 414 received RIC and 231 patients received MAC. The median follow-up time from transplantation was 6.0 years for RIC and 9.4 years for MAC. The 6-year overall survival rates for RIC and MAC were 63% (95% confidence interval [CI], 58%-68%) and 59% (95% CI, 52%-66%; P = 0.34) and progression-free survival was 52% (95% CI, 47%-57%) and 52% (95% CI, 45%-59%; P = 0.64). The 2-year cumulative incidence of nonrelapse mortality was 26% (95% CI, 21%-31%) for RIC and 29% (95% CI, 23%-34%) for MAC (P = 0.51). In terms of progression/relapse, the 2-year cumulative incidence was 10% (95% CI, 5%-19%) for RIC and 9% (95% CI, 4%-14%) for MAC (P = 0.46). Higher intensity conditioning did not seem to improve outcomes for higher-risk disease, according to mutational, cytogenetic, and clinical profile. In contrast, patients with reduced performance status, matched unrelated donors, and ASXL1 mutations appeared to benefit from RIC in terms of overall survival.

Myeloproliferative Neoplasms, Version 3.2022, NCCN Clinical Practice Guidelines in Oncology

The classic Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) consist of myelofibrosis, polycythemia vera, and essential thrombocythemia and are a heterogeneous group of clonal blood disorders characterized by an overproduction of blood cells. The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for MPN were developed as a result of meetings convened by a multidisciplinary panel with expertise in MPN, with the goal of providing recommendations for the management of MPN in adults. The Guidelines include recommendations for the diagnostic workup, risk stratification, treatment, and supportive care strategies for the management of myelofibrosis, polycythemia vera, and essential thrombocythemia. Assessment of symptoms at baseline and monitoring of symptom status during the course of treatment is recommended for all patients. This article focuses on the recommendations as outlined in the NCCN Guidelines for the diagnosis of MPN and the risk stratification, management, and supportive care relevant to MF.

Impact of molecular profiling on the management of patients with myelofibrosis

Myelofibrosis (MF) is a chronic myeloproliferative neoplasm (MPN) characterized by a highly heterogeneous clinical course, which can be complicated by severe constitutional symptoms, massive splenomegaly, progressive bone marrow failure, cardiovascular events, and development of acute leukemia. Constitutive signaling through the JAK-STAT pathway plays a fundamental role in its pathogenesis, generally due to activating mutations of JAK2, CALR and MPL genes (i.e., the MPN driver mutations), present in most MF patients. Next Generation Sequencing (NGS) panel testing has shown that additional somatic mutations can already be detected at the time of diagnosis in more than half of patients, and that they accumulate along the disease course. These mutations, mostly affecting epigenetic modifiers or spliceosome components, may cooperate with MPN drivers to favor clonal dominance or influence the clinical phenotype, and some, such as high molecular risk mutations, correlate with a more aggressive clinical course with poor treatment response. The current main role of molecular profiling in clinical practice is prognostication, principally for selecting high-risk patients who may be candidates for transplantation, the only curative treatment for MF to date. To this end, contemporary prognostic models incorporating molecular data are useful tools to discriminate different risk categories. Aside from certain clinical situations, decisions regarding medical treatment are not based on patient molecular profiling, yet this approach may become more relevant in novel treatment strategies, such as the use of vaccines against the mutant forms of JAK2 or CALR, or drugs directed against actionable molecular targets.

Improving allogeneic stem cell transplantation in myelofibrosis

In this review, we will outline dimensions in which outcome of patients with myelofibrosis undergoing curative treatment can be optimized: patient selection, transplant procedure, and posttransplant prevention or treatment of relapse. For patient selection, fortunately, as with several other hematologic malignancies, the management of patients with myelofibrosis has very much entered the molecular era, with the establishment of several driver and nondriver mutations, allowing more individualized selection for treatment. For the transplant procedure itself, different conditioning intensities do not seem to play a distinctive role with regards to outcome posttransplant but still need to be compared in the molecular era. While many patients nowadays may receive ruxolitinib before transplant, recent studies may facilitate fine-tuning and integration of ruxolitinib into the transplant algorithm. The role of novel inhibitors for the transplant setting remains unclear. For the posttransplant phase, evidence remains scarce, with experiences of donor-lymphocyte infusions for relapse management but more efforts are needed in understanding relapse and identifying and treating patients at high risk for relapse.

Posttransplantation Cyclophosphamide-based Graft versus Host Disease Prophylaxis with Non-myeloablative Conditioning for Blood or Marrow Transplantation for Myelofibrosis

We describe outcomes with posttransplantation cyclophosphamide and non-myeloablative conditioning based allogeneic blood or marrow transplantation for myelofibrosis using matched or mismatched, family or unrelated donors. The conditioning regimen consisted of fludarabine, cyclophosphamide and total body irradiation. Forty-two patients, with a median age of 63 years, were included, of whom 19% had intermediate-1, 60% had intermediate-2, and 21% had high-risk DIPSS-plus disease, and 60% had atleast one high-risk somatic mutation. Over 90% patients engrafted neutrophils at a median of 19.5 days and 7% had graft failure. At 1 and 3-years, respectively, the overall survival was 65% and 60%, relapse-free survival was 65% and 31%, relapse was 5% and 40%, and non-relapse mortality was 30% and 30%. Acute graft versus host disease grade 3-4 was noted in 17% at 1 year and chronic graft versus host disease requiring systemic therapy in 12% patients. Spleen size ≥ 17 cm or prior splenectomy was associated with inferior relapse-free survival (HR 3.50, 95% CI 1.18-10.37, P=0.02) and higher relapse rate (SDHR not calculable, P=0.01). Age > 60 years (SDHR 0.26, 95% CI: 0.08-0.80, P=0.02) and peripheral blood graft (SDHR 0.34, 95% CI 0.11-0.99, P=0.05) was associated with lower risk of relapse. In our limited sample, the presence of a high-risk mutation was not statistically significantly associated with an inferior outcome although ASXL1 was suggestive of inferior survival (SDHR 2.36. 95% CI 0.85-6.6, P=0.09). Overall, this approach shows comparable outcomes as previously reported and underscores the importance of spleen size in evaluation of transplant candidates.

Reduced intensity hematopoietic stem cell transplantation for myelofibrosis in accelerated-phase

Results of this first report in accelerated-phase myelofibrosis may encourage clinicians to refer these patients for curative treatment.

Accelerated-phase myelofibrosis without prior cytoreduction showed excellent 5-year survival (65%) but higher relapse vs chronic phase.

Accelerated-phase myelofibrosis, currently defined by circulating blasts 10% to 19%, usually confers very high risk for progression and poor outcome. The outcome of hematopoietic stem cell transplantation for accelerated-phase myelofibrosis has not been evaluated yet. We analyzed the outcome of 349 clinically and genetically annotated patients with primary or secondary myelofibrosis undergoing reduced intensity transplantation, of whom 35 had accelerated-phase myelofibrosis. In comparison with chronic-phase (<10% blasts) myelofibrosis, median leukocyte counts were higher, more patients had constitutional symptoms, and RAS mutations were detected more frequently in the accelerated-phase group. After a median follow-up of 5.9 years, estimated 5-year overall survival was 65% (95% confidence interval [CI], 49% to 81%) vs 64% (95% CI, 59% to 69%) for the chronic-phase group (P = .91), and median overall survival was not reached. In terms of relapse-free survival, estimated 5-year outcome for the accelerated-phase group was 49% (95% CI, 32% to 67%) vs 55% (95% CI, 50% to 61%) for the chronic-phase group (P = .65). Estimated 5-year nonrelapse mortality was 20% (95% CI, 8% to 33%) for the accelerated-phase group vs 30% (95% CI, 24% to 35%; P = .25) for the chronic-phase group. In terms of relapse, 5-year incidence was 30% (95% CI, 14% to 46%) for the accelerated-phase group vs 15% (95% CI, 11% to 19%) for the chronic-phase group (P = .02). Results were confirmed in multivariable analysis and propensity score matching. In conclusion, reduced intensity transplantation showed excellent survival but higher relapse for accelerated-phase myelofibrosis.

Allogeneic blood or marrow transplantation with haploidentical donor and post-transplantation cyclophosphamide in patients with myelofibrosis: a multicenter study

We report the results from a multicenter retrospective study of 69 adult patients who underwent haploidentical blood or marrow transplantation (haplo-BMT) with post-transplantation cyclophosphamide (PTCy) for chronic phase myelofibrosis. The median age at BMT was 63 years (range, 41-74). Conditioning regimens were reduced intensity in 54% and nonmyeloablative in 39%. Peripheral blood grafts were used in 86%. The median follow-up was 23.1 months (range, 1.6-75.7). At 3 years, the overall survival, relapse-free survival (RFS), and graft-versus-host-disease (GVHD)-free-RFS were 72% (95% CI 59-81), 44% (95% CI 29-59), and 30% (95% CI 17-43). Cumulative incidences of non-relapse mortality and relapse were 23% (95% CI 14-34) and 31% (95% CI 17-47) at 3 years. Spleen size ≥22 cm or prior splenectomy (HR 6.37, 95% CI 2.02-20.1, P = 0.002), and bone marrow grafts (HR 4.92, 95% CI 1.68-14.4, P = 0.004) were associated with increased incidence of relapse. Cumulative incidence of acute GVHD grade 3-4 was 10% at 3 months and extensive chronic GVHD was 8%. Neutrophil engraftment was reported in 94% patients, at a median of 20 days (range, 14-70). In conclusion, haplo-BMT with PTCy is feasible in patients with myelofibrosis. Splenomegaly ≥22 cm and bone marrow grafts were associated with a higher incidence of relapse in this study.

Outcomes of Allogeneic Hematopoietic Cell Transplantation in Patients With Myelofibrosis-A Systematic Review and Meta-Analysis

Allogeneic hematopoietic cell transplant (allo-HCT) remains the only potentially curative therapeutic modality for patients with primary or secondary myelofibrosis (MF). However, many patients are considered ineligible for allo-HCT, and transplant-related mortality can be substantial. Data on the efficacy and safety of allo-HCT are mixed and largely derived from retrospective studies. We aimed to synthesize the available evidence on the safety and efficacy of allo-HCT in MF and to identify patient, disease, and transplant characteristics with prognostic impact on outcomes of patients with MF undergoing allo-HCT. For this systematic review and meta-analysis, Cochrane Library, Google Scholar, Ovid Medline, Ovid Embase, PubMed, Scopus, and Web of Science Core Collection were searched from inception to October 11, 2020, for studies on allo-HCT in MF. Random-effects models were used to pool response rates for the co-primary outcomes of 1-year, 2-year, and 5-year overall survival (OS). Rates of non-relapse mortality and acute and chronic graft-versus-host-disease (GVHD) were studied as secondary endpoints. Subgroup analyses on the effect of conditioning regimen intensity, baseline dynamic international prognostic scoring system (DIPSS) score, and patient age were performed. The study protocol has been registered on PROSPERO (CRD42020188706). Forty-three studies with 8739 patients were identified and included in this meta-analysis. Rates of 1-year, 2-year, and 5-year OS were 66.7% (95% confidence interval [CI], 63.5%-69.8%), 64.4% (95% CI, 57.6%-70.6%), and 55.0% (95% CI, 51.8%-58.3%), respectively. Rates of 1-year, 2-year, and 5-year nonrelapse mortality were 25.9% (95% CI, 23.3%-28.7%), 29.7% (95% CI, 24.5%-35.4%), and 30.5% (95% CI, 25.9%-35.5%), respectively. The combined rate of graft failure was 10.6% (95% CI, 8.9%-12.5%) with primary and secondary graft failure occurring in 7.3% (95% CI, 5.7%-9.4%) and 5.9% (95% CI, 4.3%-8.0%) of patients, respectively. Rates of acute and chronic graft-versus-host disease were 44.0% (95% CI, 39.6%-48.4%; grade III/IV: 15.2%) and 46.5% (95% CI, 42.2%-50.8%; extensive or moderate/severe: 26.1%), respectively. Subgroup analyses did not show any significant difference between conditioning regimen intensity (myeloablative versus reduced-intensity), median patient age, and proportion of DIPSS-intermediate-2/high patients. The quality of the evidence is limited by the absence of randomized clinical trials in the field and the heterogeneity of patient and transplant characteristics across included studies. Given the poor prognosis of patients not receiving transplants and in the absence of curative nontransplantation therapies, our results support consideration of allo-HCT for eligible patients with MF.

McLornan D, Yakoub‐Agha I. Allogeneic hematopoietic cell transplantation in older myelofibrosis patients: A study of the chronic malignancies working party of EBMT and the Spanish Myelofibrosis Registry

Allogeneic hematopoietic cell transplantation (allo-HCT) is increasingly used in older myelofibrosis (MF) patients, but its risk/benefit ratio compared to non-transplant approaches has not been evaluated in this population. We analyzed the outcomes of allo-HCT in 556 MF patients aged ≥65 years from the EBMT registry, and determined the excess mortality over the matched general population of MF patients ≥65 years managed with allo-HCT (n = 556) or conventional drug treatment (n = 176). The non-transplant cohort included patients with intermediate-2 or high risk DIPSS from the Spanish Myelofibrosis Registry. After a median follow-up of 3.4 years, the estimated 5-year survival rate, non-relapse mortality (NRM), and relapse incidence after transplantation was 40%, 37%, and 25%, respectively. Busulfan-based conditioning was associated with decreased mortality (HR: 0.7, 95% CI: 0.5-0.9) whereas the recipient CMV+/donor CMV- combination (HR: 1.7, 95% CI: 1.2-2.4) and the JAK2 mutated genotype (HR: 1.9, 95% CI: 1.1-3.5) predicted higher mortality. Busulfan-based conditioning correlated with improved survival due to less NRM, despite its higher relapse rate when compared with melphalan-based regimens. Excess mortality was higher in transplanted patients than in the non-HCT cohort in the first year of follow-up (ratio: 1.93, 95% CI: 1.13-2.80), whereas the opposite occurred between the fourth and eighth follow-up years (ratio: 0.31, 95% CI: 0.18-0.53). Comparing the excess mortality of the two treatments, male patients seemed to benefit more than females from allo-HCT, mainly due to their worse prognosis with non-transplant approaches. These findings could potentially enhance counseling and treatment decision-making in elderly transplant-eligible MF patients.

Classical Philadelphia-negative myeloproliferative neoplasms (MPNs): A continuum of different disease entities

Classical Philadelphia-negative myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell-derived disorders characterized by uncontrolled proliferation of differentiated myeloid cells and close pathobiologic and clinical features. According to the 2016 World Health Organization (WHO) classification, MPNs include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). The 2016 revision aimed in particular at strengthening the distinction between masked PV and JAK2-mutated ET, and between prefibrotic/early (pre-PMF) and overt PMF. Clinical manifestations in MPNs include constitutional symptoms, microvascular disorders, thrombosis and bleeding, splenomegaly secondary to extramedullary hematopoiesis, cytopenia-related symptoms, and progression to overt MF and acute leukemia. A dysregulation of the JAK/STAT pathway is the unifying mechanistic hallmark of MPNs, and is guided by somatic mutations in driver genes including JAK2, CALR and MPL. Additional mutations in myeloid neoplasm-associated genes have been also identified, with established prognostic relevance, particularly in PMF. Prognostication of MPN patients relies on disease-specific clinical models. The increasing knowledge of MPN biology led to the development of integrated clinical and molecular prognostic scores that allow a more refined stratification. Recently, the therapeutic landscape of MPNs has been revolutionized by the introduction of potent, selective JAK inhibitors (ruxolitinib, fedratinib), that proved effective in controlling disease-related symptoms and splenomegaly, yet leaving unmet critical needs, owing the lack of disease-modifying activity. In this review, we will deal with molecular, clinical, and therapeutic aspects of the three classical MPNs aiming at highlighting either shared characteristics, that overall define a continuum within a single disease family, and uniqueness, at the same time.

Allogeneic haematopoietic cell transplantation for myelofibrosis: proposed definitions and management strategies for graft failure, poor graft function and relapse: best practice recommendations of the EBMT Chronic Malignancies Working Party

Allogeneic haematopoietic cell transplantation (allo-HCT) remains the only curative approach in myelofibrosis (MF). Despite advances over recent decades, relapse and non-relapse mortality rates remain significant. Relapse rates vary between 15 and 25% across retrospective studies and management strategies vary widely, ranging from palliation to adoptive immunotherapy and, in some cases, a second allo-HCT. Moreover, in allo-HCT, there is a higher incidence of poor graft function and graft failure due to splenomegaly and a hostile "pro-inflammatory" marrow niche. The Practice Harmonisation and Guidelines subcommittee of the Chronic Malignancies Working Party (CMWP) of EBMT convened an international panel consisting of transplant haematologists, histopathologists and molecular biologists to propose practical, clinically relevant definitions of graft failure, poor graft function and relapse as well as management strategies following allo-HCT. A systematic approach to molecular monitoring, histopathological assessment and chimerism testing is proposed. These proposed recommendations aim to increase the accuracy and uniformity of reporting and to thereby facilitate the development of more consistent approaches to these challenging issues. In addition, we propose management strategies for these complications.

Integration of Molecular Information in Risk Assessment of Patients with Myeloproliferative Neoplasms

Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) are clonal disorders of a hematopoietic stem cell, characterized by an abnormal proliferation of largely mature cells driven by mutations in JAK2, CALR, and MPL. All these mutations lead to a constitutive activation of the JAK-STAT signaling, which represents a target for therapy. Beyond driver ones, most patients, especially with myelofibrosis, harbor mutations in an array of "myeloid neoplasm-associated" genes that encode for proteins involved in chromatin modification and DNA methylation, RNA splicing, transcription regulation, and oncogenes. These additional mutations often arise in the context of clonal hematopoiesis of indeterminate potential (CHIP). The extensive characterization of the pathologic genome associated with MPN highlighted selected driver and non-driver mutations for their clinical informativeness. First, driver mutations are enlisted in the WHO classification as major diagnostic criteria and may be used for monitoring of residual disease after transplantation and response to treatment. Second, mutation profile can be used, eventually in combination with cytogenetic, histopathologic, hematologic, and clinical variables, to risk stratify patients regarding thrombosis, overall survival, and rate of transformation to secondary leukemia. This review outlines the molecular landscape of MPN and critically interprets current information for their potential impact on patient management.

JAK Be Nimble: Reviewing the Development of JAK Inhibitors and JAK Inhibitor Combinations for Special Populations of Patients with Myelofibrosis

Myelofibrosis (MF) is a myeloproliferative neoplasm hallmarked by uncontrolled blood counts, constitutional symptoms, extramedullary hematopoiesis, and an increased risk of developing acute myeloid leukemia. Janus kinase (JAK) inhibitors are the most common treatment for MF due to their ability to reduce spleen size and improve disease-related symptoms; however, JAK inhibitors are not suitable for every patient and their impact on MF is limited in several respects. Novel JAK inhibitors and JAK inhibitor combinations are emerging that aim to enhance the treatment landscape, providing deeper responses to a broader population of patients with the continued hope of providing disease modification and improving long-term outcomes. In this review, we highlight several specific areas of unmet need within MF. Subsequently, we review agents that target those areas of unmet need, focusing specifically on the JAK inhibitors, momelotinib, pacritinib, itacitinib, and NS-018 as well as JAK inhibitor combination approaches using CPI-0610, navitoclax, parsaclisib, and luspatercept.

Calreticulin mutations in myeloproliferative neoplasms

Calreticulin (CALR) is a chaperone present in the endoplasmic reticulum, which is involved in the quality control of N-glycosylated proteins and storage of calcium ions. In 2013, the C-terminal mutation in CALR was identified in half of the patients with essential thrombocythemia and primary myelofibrosis who did not have a JAK2 or MPL mutation. The results of 8 years of intensive research are changing the clinical practice associated with treating myeloproliferative neoplasms (MPNs). The presence or absence of CALR mutations and their mutation types already provide important information for diagnosis and treatment decision making. In addition, the interaction with the thrombopoietin receptor MPL, which is the main mechanism of transformation by CALR mutation, and the expression of the mutant protein on the cell surface have a great potential as targets for molecular-targeted drugs and immunotherapy. This chapter presents recent findings on the clinical significance of the CALR mutation and the molecular basis by which this mutation drives MPNs.

The Prevalence of TET2 Gene Mutations in Patients with BCR-ABL-Negative Myeloproliferative Neoplasms (MPN): A Systematic Review and Meta-Analysis

Multiple recurrent somatic mutations have recently been identified in association with myeloproliferative neoplasms (MPN). This meta-analysis aims to assess the pooled prevalence of TET2 gene mutations among patients with MPN. Six databases (PubMed, Scopus, ScienceDirect, Google Scholar, Web of Science and Embase) were searched for relevant studies from inception till September 2020, without language restrictions. The eligibility criteria included BCR-ABL-negative MPN adults with TET2 gene mutations. A random-effects model was used to estimate the pooled prevalence with 95% confidence intervals (CIs). Subgroup analyses explored results among different continents and countries, WHO diagnostic criteria, screening methods and types of MF. Quality assessment was undertaken using the Joanna Briggs Institute critical appraisal tool. The study was registered with PROSPERO (CRD42020212223). Thirty-five studies were included (n = 5121, 47.1% female). Overall, the pooled prevalence of TET2 gene mutations in MPN patients was 15.5% (95% CI: 12.1-19.0%, I2 = 94%). Regional differences explained a substantial amount of heterogeneity. The prevalence of TET2 gene mutations among the three subtypes PV, ET and MF were 16.8%, 9.8% and 15.7%, respectively. The quality of the included studies was determined to be moderate-high among 83% of the included studies. Among patients with BCR-ABL-negative MPN, the overall prevalence of TET2 gene mutations was 15.5%.

Recent Advances in the Use of Molecular Analyses to Inform the Diagnosis and Prognosis of Patients with Polycythaemia Vera

Genetic studies in the past decade have improved our understanding of the molecular basis of the BCR-ABL1-negative myeloproliferative neoplasm (MPN) polycythaemia vera (PV). Such breakthroughs include the discovery of the JAK2V617F driver mutation in approximately 95% of patients with PV, as well as some very rare cases of familial hereditary MPN caused by inherited germline mutations. Patients with PV often progress to fibrosis or acute myeloid leukaemia, both associated with very poor clinical outcome. Moreover, thrombosis and major bleeding are the principal causes of morbidity and mortality. As a result of increasingly available and economical next-generation sequencing technologies, mutational studies have revealed the prognostic relevance of a few somatic mutations in terms of thrombotic risk and risk of transformation, helping to improve the risk stratification of patients with PV. Finally, knowledge of the molecular basis of PV has helped identify targets for directed therapy. The constitutive activation of the tyrosine kinase JAK2 is targeted by ruxolitinib, a JAK1/JAK2 tyrosine kinase inhibitor for PV patients who are resistant or intolerant to cytoreductive treatment with hydroxyurea. Other molecular mechanisms have also been revealed, and numerous agents are in various stages of development. Here, we will provide an update of the recent published literature on how molecular testing can improve the diagnosis and prognosis of patients with PV and present recent advances that may have prognostic value in the near future.

Allogeneic Hemopoietic Stem Cell Transplantation for Myelofibrosis: 2021

The aim of this review is to update the current status of allogeneic hemopoietic stem cell transplants (HSCT) for patients with myelofibrosis (MF). We have first summarized the issue of an indication for allogeneic HSCT, discussing several prognostic scoring systems, developed to predict the outcome of MF, and therefore to identify patients who will benefit of an allogeneic HSCT. Patients with low risk MF are usually not selected for a transplant, whereas patients with intermediate or high risk MF are eligible. A separate issue, is how to predict the outcome of HSCT: we will outline a clinical molecular myelofibrosis transplant scoring system (MTSS), which predicts overall survival, ranging from 90% for low risk patients, to 20% for very high risk patients. We will also discuss transfusion burden and spleen size, as predictors of transplant outcome. The choice of a transplant platform including the conditioning regimen, the stem cell source and GvHD prophylaxis, are crucial for a successful program in MF, and will be outlined. Complications such as poor graft function, graft failure, GvHD and relapse of the disease, will also be reviewed. Finally we discuss monitoring the disease after HSCT with donor chimerism, driver mutations and hematologic data. We have made an effort to make this review as comprehensive and up to date as possible, and we hope it will provide some useful data for the clinicians.

Allogeneic haematopoietic cell transplantation for myelofibrosis: a real-life perspective

Myelofibrosis (MF) is a clonal stem cell neoplasm with heterogeneous clinical phenotypes and well-established molecular drivers. Allogeneic haematopoietic stem cell transplantation (HSCT) offers an important curative treatment option for primary MF and post-essential thrombocythaemia/polycythaemia vera MF or secondary MF. With a disease course that varies from indolent to highly progressive, we are now able to stratify risk of mortality through various tools including patient-related clinical characteristics as well as molecular genetic profile. Owing to the high risk of mortality and morbidity associated with HSCT for patients with myelofibrosis, it is important to improve patient selection for transplant. Our primary goal is to comprehensively define our understanding of current practices including the role of Janus Kinase (JAK) inhibitors, to present the data behind transplantation before and after leukaemic transformation, and to introduce novel personalization of MF treatment with a proposed clinical-molecular prognostic model to help elucidate a timepoint optimal for consideration of HSCT.

Outcomes following second allogeneic haematopoietic cell transplantation in patients with myelofibrosis: a retrospective study of the Chronic Malignancies Working Party of EBMT

Therapeutic management of patients with primary or secondary myelofibrosis (MF) who experience relapse or graft failure following allogeneic haematopoietic cell transplantation (allo-HCT) remains heterogeneous. We retrospectively analyzed 216 patients undergoing a second allo-HCT for either relapse (56%) or graft failure (31%) between 2010 and 2017. Median age was 57.3 years (range 51-63). The same donor as for the first allo-HCT was chosen in 66 patients (31%) of whom 19 received an HLA-identical sibling donor, whereas a different donor was chosen for 116 patients (54%). Median follow-up was 40 months. Three-year overall survival (OS) and relapse-free survival (RFS) were 42% and 39%, respectively. Three-year non-relapse mortality (NRM) and relapse rates were 36% and 25%, respectively. Grade II-IV and III-IV acute GVHD occurred in 25% and 11% of patients, respectively, and the 3-year incidence of chronic GVHD was 33% including 14% for extensive grade. Graft-failure incidence at 1 year was 14%. In conclusion, our data suggest that a second allo-HCT is a potential option for patients failing first allo-HCT for MF albeit careful patient assessment is fundamental to identify individual patients who could benefit from this approach.

Epigenetic Dysregulation of Myeloproliferative Neoplasms

This article reviews the genetic data on epigenetic modifying mutations in myeloproliferative neoplasms and their clinical implications, preclinical studies exploring our current understanding of how mutations in epigenetic modifying proteins cooperate with myeloproliferative neoplasms drivers to promote disease progression, and recent advances in novel therapeutics supporting the role of targeting epigenetic pathways to treat fibrotic progression.

Targeting Abnormal Hematopoietic Stem Cells in Chronic Myeloid Leukemia and Philadelphia Chromosome-Negative Classical Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPNs) are unique hematopoietic stem cell disorders sharing mutations that constitutively activate the signal-transduction pathways involved in haematopoiesis. They are characterized by stem cell-derived clonal myeloproliferation. The key MPNs comprise chronic myeloid leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). CML is defined by the presence of the Philadelphia (Ph) chromosome and BCR-ABL1 fusion gene. Despite effective cytoreductive agents and targeted therapy, complete CML/MPN stem cell eradication is rarely achieved. In this review article, we discuss the novel agents and combination therapy that can potentially abnormal hematopoietic stem cells in CML and MPNs and the CML/MPN stem cell-sustaining bone marrow microenvironment.

Impact of spleen size and splenectomy on outcomes of allogeneic hematopoietic cell transplantation for myelofibrosis: A retrospective analysis by the chronic malignancies working party on behalf of European society for blood and marrow transplantation (EBMT)

The role of spleen size and splenectomy for the prediction of post-allogeneic hematopoietic stem cell transplant (allo-HCT) outcome in myelofibrosis remains under debate. In EBMT registry, we identified a cohort of 1195 myelofibrosis patients transplanted between 2000-2017 after either fludarabine-busulfan or fludarabine-melphalan regimens. Overall, splenectomy was performed in 202 (16.9%) patients and its use decreased over time (28.3% in 2000-2009 vs 14.1% in 2010-2017 period). By multivariate analysis, splenectomy was associated with less NRM (HR 0.64, 95% CI 0.44-0.93, P = .018) but increased risk of relapse (HR 1.43, 95% CI 1.01-2.02, P = .042), with no significant impact on OS (HR 0.86, 95% CI 0.67-1.12, P = .274). However, in subset analysis comparing the impact of splenectomy vs specific spleen sizes, for patients with progressive disease, an improved survival was seen in splenectomised subjects compared to those patients with a palpable spleen length ≥ 15 cm (HR 0.44, 95% CI 0.28-0.69, P < .001), caused by a significant reduction in NRM (HR 0.26, 95% CI 0.14-0.49, P < .001), without significantly increased relapse risk (HR 1.47, 95% CI 0.87-2.49, P = .147). Overall, despite the possible biases typical of retrospective cohorts, this study highlights the potential detrimental effect of massive splenomegaly in transplant outcome and supports the role of splenectomy for myelofibrosis patients with progressive disease and large splenomegaly.

Current clinical strategies and emergent treatment landscapes in leukemic transformation of Philadelphia-negative myeloproliferative neoplasms

Introduction: Transformation to acute myeloid leukemia (AML) of Philadelphia chromosome-negative (Ph-) chronic myeloproliferative neoplasms (MPN) represents a challenging medical concern and an unmet clinical need, since it charts a very poor outcome and a low rate of response to standard treatments with the exception of allogeneic hematopoietic stem cell transplantation (HSCT). Recent novel insights into the molecular disease pathways and the genomic features characterizing the transformation of Ph-MPN have led to new therapeutic individualized approaches with the potential to modify the clinical management of these difficult-to-treat patients. Areas covered: Literature review (MeSH headings/PubMed) of risk factors of MPNs progression and treatment options for transformed disease with traditional standard approaches, and novel and investigational agents was performed. One or combinations of related subject headings like transformed MPN, epigenetics, molecular alterations, HSCT, ruxolitinib, azacytidine, decitabine, gliterinib, novel agents, personalized therapy was screened. Informative papers were selected by the appropriate actual evidence and suggesting strategies for improving outcomes in the future. Expert opinion: Current and emerging treatments for transformed Ph-MPN, are presented. Novel targeted or experimental agents to be used both before HSCT, to induce blast-free state, or to modify the disease prognosis and improve survival and quality of life are critically reviewed.

Genomics of MPN progression

The Philadelphia chromosome-negative (Ph-) myeloproliferative neoplasms (MPNs) are a heterogenous group of hematopoietic stem cell diseases characterized by activated JAK/STAT signaling and a variable propensity toward myelofibrotic and leukemic transformation. Acquisition of somatic mutations in addition to the canonical JAK2, MPL, and CALR mutations found in MPNs is an important catalyst in the clonal evolution and progression of these disorders. In recent years, our increasing understanding of the molecular landscape of Ph- MPNs has generated important prognostic information that informs our approach to risk stratification and therapeutic decision-making. This review will focus on the critical impact of genomics on our approach to management of advanced Ph- MPNs.

Impact of Mutational Profile on the Management of Myeloproliferative Neoplasms: A Short Review of the Emerging Data

Philadelphia-chromosome negative myeloproliferative neoplasms (MPN) are a heterogeneous group of clonal hematopoietic stem cell disorders characterized by an increased risk of thrombosis and progression to acute myeloid leukemia. MPN are associated with driver mutations in JAK2, CALR and MPL which are crucial for the diagnosis and lead to a constitutive activation of the JAK-STAT signaling, independent of cytokine regulation. Moreover, most patients have concomitant mutations in genes involved in DNA methylation, chromatin modification, messenger RNA splicing, transcription regulation and signal transduction. These additional mutations may arise before, in the context of clonal hematopoiesis of indeterminate potential (CHIP), or after the acquisition of the driver mutation. The clinical phenotype of MPN results from complex interactions between mutations and host factors. The increased application of next-generation sequencing (NGS) techniques to a large series of patients with MPN has expanded the knowledge of mutational landscape and contributed to define the clinical significance of mutations. This molecular information is being increasingly used to refine diagnosis, risk stratification, monitoring of residual disease and response to treatment. ASXL1, SRSF2, EZH2, IDH1/IDH2 and U2AF1 mutations are associated with a more advanced disease and reduced overall survival in primary myelofibrosis (PMF), whereas spliceosome mutations in Polycythemia vera (PV) and essential thrombocythemia (ET) adversely affect both overall (SF3B1, SRSF2 in ET and SRSF2 in PV) and myelofibrosis-free (U2AF1, SF3B1 in ET) survival. This review discusses current knowledge of the molecular landscape of MPN, and how the availability of those molecular information may impact patient management.

The Genetic Basis of Primary Myelofibrosis and Its Clinical Relevance

Among classical BCR-ABL-negative myeloproliferative neoplasms (MPN), primary myelofibrosis (PMF) is the most aggressive subtype from a clinical standpoint, posing a great challenge to clinicians. Whilst the biological consequences of the three MPN driver gene mutations (JAK2, CALR, and MPL) have been well described, recent data has shed light on the complex and dynamic structure of PMF, that involves competing disease subclones, sequentially acquired genomic events, mostly in genes that are recurrently mutated in several myeloid neoplasms and in clonal hematopoiesis, and biological interactions between clonal hematopoietic stem cells and abnormal bone marrow niches. These observations may contribute to explain the wide heterogeneity in patients' clinical presentation and prognosis, and support the recent effort to include molecular information in prognostic scoring systems used for therapeutic decision-making, leading to promising clinical translation. In this review, we aim to address the topic of PMF molecular genetics, focusing on four questions: (1) what is the role of mutations on disease pathogenesis? (2) what is their impact on patients' clinical phenotype? (3) how do we integrate gene mutations in the risk stratification process? (4) how do we take advantage of molecular genetics when it comes to treatment decisions?

Salvage Therapy Using Azacitidine for Relapsed Primary Myelofibrosis after Cord Blood Transplantation

We present the case of a 53-year-old woman with prefibrotic stage primary myelofibrosis (PMF) who underwent cord blood transplantation. Nine years after transplantation, she relapsed, which was confirmed by a bone marrow examination. We decided to treat her using azacitidine. After three courses of azacitidine, a partial cytogenetic response was confirmed. Azacitidine maintenance therapy successfully maintained a low level of recipient-origin peripheral blood cells with a stable hematological condition. Azacitidine may therefore be a promising therapeutic option for PMF patients who relapse after allogeneic stem cell transplantation.

[The prognostic value of ASXL1 mutation in primary myelofibrosis. Literature review and clinical case description]

Primary myelofibrosis is a myeloproliferative neoplasm that occurs de novo, characterized by clonal proliferation of stem cells, abnormal expression of cytokines, bone marrow fibrosis, hepatosplenomegaly as a result of extramedullary hematopoiesis, symptoms of tumor intoxication, cachexemia, peripheral blood leukoerythroblastosis, leukemic progression and low survival. Primary myelofibrosis is a chronic incurable disease. The aims of therapy: preventing progression, increasing overall survival, improving quality of life. The choice of therapeutic tactics is limited. Allogenic hematopoietic stem cell transplantation is the only method that gives a chance for a cure. The role of mutations in a number of genes in the early identification of candidates for allogeneic hematopoietic stem cell transplantation is being actively studied. The article describes the clinical case of the detection ofASXL1gene mutations in a patient with prefibrous primary myelofibrosis. The diagnosis was established on the basis of WHO criteria 2016. The examination revealed a mutation ofASXL1. Interferon alfa therapy is carried out, against the background of which clinico-hematological remission has been achieved. Despite the identified mutation, the patient is not a candidate for allogeneic hematopoietic stem cell transplantation. Given the unfavorable prognostic value of theASXL1mutation, the patient is subject to active dynamic observation and aggressive therapeutic tactics when signs of disease progression appear.

Next Generation Sequencing in MPNs. Lessons from the Past and Prospects for Use as Predictors of Prognosis and Treatment Responses

The myeloproliferative neoplasms (MPNs) are acquired hematological stem cell neoplasms characterized by driver mutations in JAK2, CALR, or MPL. Additive mutations may appear in predominantly epigenetic regulator, RNA splicing and signaling pathway genes. These molecular mutations are a hallmark of diagnostic, prognostic, and therapeutic assessment in patients with MPNs. Over the past decade, next generation sequencing (NGS) has identified multiple somatic mutations in MPNs and has contributed substantially to our understanding of the disease pathogenesis highlighting the role of clonal evolution in disease progression. In addition, disease prognostication has expanded from encompassing only clinical decision making to include genomics in prognostic scoring systems. Taking into account the decreasing costs and increasing speed and availability of high throughput technologies, the integration of NGS into a diagnostic, prognostic and therapeutic pipeline is within reach. In this review, these aspects will be discussed highlighting their role regarding disease outcome and treatment modalities in patients with MPNs.

Early Mixed Lymphoid Donor/Host Chimerism is Associated with Improved Transplant Outcome in Patients with Primary or Secondary Myelofibrosis

We investigated risk factors for the development of mixed chimerism in 131 patients who underwent transplantation for myelofibrosis and determined the impact of lymphoid (CD3+) and myeloid (CD33+) chimerism on transplant outcome. Disease risk included DIPSS plus categories low to high. The median patient age was 58 years. Patients were conditioned with high-intensity (myeloablative) or low/reduced-intensity (nonmyeloablative) regimens and received a transplant from a related or unrelated donor. Mixed CD3⁺ chimerism was observed earlier after HCT, whereas CD33⁺ chimerism occurred later. Mixed chimerism was more frequent with low-intensity regimens than with high- intensity regimens. Mixed CD3⁺ chimerism did not lead to graft failure and was associated with a reduced incidence of acute GVHD and improved overall survival (OS) and relapse-free survival, whereas mixed CD33⁺ chimerism was associated with an increased incidence of relapse and reduced OS and relapse-free survival, independent of the CD34⁺ cell dose transplanted. Thus, mixed CD3⁺ chimerism in patients with myelofibrosis had a favorable impact on transplantation outcome and does not require therapeutic interventions.

Current and future therapies for myelofibrosis

Myelofibrosis is classified as a 'Philadelphia-chromosome negative' clonal myeloproliferative disorder. The heterogeneity of this condition and patient population and array of often challenging clinical manifestations can frequently make therapeutic decisions challenging. Despite many advances in therapy with targeted and combination approaches, following an enhanced understanding of underlying disease pathogenesis, cure only remains achievable with allogeneic stem cell transplant. This option is often limited to a small group of younger transplant-eligible patients with more advanced disease who have both a suitable donor and no or few co-morbidities. In this article, we will discuss up-to-date disease prognostication, common clinical challenges associated with myelofibrosis and both standard and novel therapeutic approaches. Increasingly complex prognostic modelling utilises patient-specific, haematological and genomic parameters to improve the accuracy of risk assessment and predict disease progression. We will also focus on difficult clinical scenarios such as disease-associated anaemia, thrombocytopenia and extremes of age. Future and evolving therapies within this field are highly anticipated and novel JAK inhibitor and non-JAK inhibitor-based therapy will also be discussed, including the new challenge of how to switch from one JAK inhibitor therapy to another.

Determinants of survival in myelofibrosis patients undergoing allogeneic hematopoietic cell transplantation

We aimed to evaluate the determinants of survival in myelofibrosis patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT) and to describe factors predicting the main post-HCT complications. This retrospective study by the European Society for Blood and Marrow Transplantation included 2916 myelofibrosis patients who underwent first allo-HCT from an HLA-identical sibling or unrelated donor between 2000 and 2016. After a median follow-up of 4.7 years from transplant, projected median survival of the series was 5.3 years. Factors independently associated with increased mortality were age ≥ 60 years and Karnofsky Performance Status <90% at transplant, and occurrence of graft failure, grades III-IV acute graft-vs.-host disease (aGVHD), and disease progression/relapse during follow-up. The opposing effects of chronic graft-vs.-host disease (GVHD) on non-relapse mortality and relapse incidence resulted in a neutral influence on survival. Graft failure increased in unrelated donor recipients and decreased with myeloablative conditioning (MAC) and negative donor/recipient cytomegalovirus serostatus. Risk of grades III-IV aGVHD was higher with unrelated donors and decreased with MAC. Relapse incidence tended to be higher in patients with intermediate-2/high-risk DIPSS categories and to decrease in CALR-mutated patients. Acute and chronic GVHD reduced the subsequent risk of relapse. This information has potential implications for patient counseling and clinical decision-making.

Mutant calreticulin in myeloproliferative neoplasms

Recurrent mutations in calreticulin are present in ∼20% of patients with myeloproliferative neoplasms (MPNs). Since its discovery in 2013, we now have a more precise understanding of how mutant CALR, an endoplasmic reticulum chaperone protein, activates the JAK/STAT signaling pathway via a pathogenic binding interaction with the thrombopoietin receptor MPL to induce MPNs. In this Spotlight article, we review the current understanding of the biology underpinning mutant CALR-driven MPNs, discuss clinical implications, and highlight future therapeutic approaches.

The Mixture of Autoregressive Hidden Markov Models of Morphology for Dentritic Spines During Activation Process

The dendritic spines play a crucial role in learning and memory processes, epileptogenesis, drug addiction, and postinjury recovery. The shape of the dendritic spine is a morphological key to understand learning and memory process. The classification of the dendritic spines is based on their shapes but the major questions are how the shapes changes in time, how the synaptic strength changes, and is there a correlation between shapes and synaptic strength? Because the changes of the classes by dendritic spines during activation are time dependent, the forward-directed autoregressive hidden Markov model (ARHMM) can be used to model these changes. It is also more appropriate to use an ARHMM directed backward in time. Thus, the mixture of forward-directed ARHMM and backward-directed ARHMM (MARHMM) is used to model time-dependent data related to the dendritic spines. In this article, we discuss (1) how to choose the initial probability vector and transition and dependence matrices in ARHMM and MARHMM for modeling the dendritic spines changes and (2) how to estimate these matrices. Many descriptors to classify dendritic spines in two-dimensional or/and three-dimensional (3D) are available. Our results from sensitivity analysis show that the classification that comes from 3D descriptors is closer to the truth, and estimated transition and dependence probability matrices are connected with the molecular mechanism of the dendritic spines activation.