Risk factors and a prognostic model for postsplenectomy survival in myelofibrosis

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.

Momelotinib expands the therapeutic armamentarium for myelofibrosis: Impact on hierarchy of treatment choices

The primary objective of treatment in myelofibrosis (MF) is prolongation of life, which is currently accomplished only by allogeneic hematopoietic stem cell transplantation (AHSCT). Determination of optimal timing for AHSCT is facilitated by molecular risk stratification. Non-transplant treatment options in MF are palliative in scope and include Janus kinase 2 (JAK2) inhibitors (JAKi): momelotinib (FDA approved on September 15, 2023), ruxolitinib (November 16, 2011), fedratinib (August 16, 2019), and pacritinib (February 28, 2022); all four JAKi are effective in reducing spleen size and alleviating symptoms, considered a drug class effect and attributed to their canonical JAK-STAT inhibitory mechanism of action. In addition, momelotinib exhibits erythropoietic effect, attributed to alleviation of ineffective erythropoiesis through inhibition of activin A receptor type-I (ACVR1). In transplant-ineligible or deferred patients, the order of treatment preference is based on specific symptoms and individual assessment of risk tolerance. Because of drug-induced immunosuppression and other toxicities attributed to JAKi, we prefer non-JAKi drugs as initial treatment for MF-associated anemia that is not accompanied by treatment-requiring splenomegaly or constitutional symptoms. Otherwise, it is reasonable to consider momelotinib as the first-line JAKi treatment of choice, in order to target the triad of quality-of-life offenders in MF: anemia, splenomegaly, and constitutional symptoms/cachexia. For second-line therapy, we favor ruxolitinib, over fedratinib, based on toxicity profile. Pacritinib and fedratinib provide alternative options in the presence of severe thrombocytopenia or ruxolitinib-resistance/intolerance, respectively. Splenectomy remains a viable option for drug-resistant symptomatic splenomegaly and cytopenia.

Momelotinib: an emerging treatment for myelofibrosis patients with anemia

The suite of marked anemia benefits that momelotinib has consistently conferred on myelofibrosis (MF) patients stem from its unique inhibitory activity on the BMP6/ACVR1/SMAD and IL-6/JAK/STAT3 pathways, resulting in decreased hepcidin (master iron regulator) expression, higher serum iron and hemoglobin levels, and restored erythropoiesis. Clinical data on momelotinib from the phase 2 and the two phase 3 SIMPLIFY trials consistently demonstrated high rates of sustained transfusion-independence. In a recent phase 2 translational study, 41% of the patients achieved transfusion independence for ≥ 12 weeks. In the phase 3 trials SIMPLIFY-1 and SIMPLIFY-2, 17% more JAK inhibitor-naïve patients and two-fold more JAK inhibitor-treated patients achieved or maintained transfusion independence with momelotinib versus ruxolitinib and best available therapy (89% ruxolitinib), respectively. Anemia is present in approximately a third of MF patients at diagnosis, eventually developing in nearly all patients. The need for red blood cell transfusions is an independent adverse risk factor for both overall survival and leukemic transformation. Presently, FDA-approved medications to address anemia are lacking. Momelotinib is one of the prime candidates to durably address the critical unmet needs of MF patients with moderate/severe anemia. Importantly, momelotinib may have overall survival benefits in frontline and second-line MF patients. MOMENTUM is an international registration-track phase 3 trial further assessing momelotinib’s unique constellation of anemia and other benefits in second-line MF patients; the results of the MOMENTUM trial are keenly awaited and may lead to regulatory approval of momelotinib.

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.

Splenectomy before allogeneic hematopoietic cell transplantation for myelofibrosis: A French nationwide study

The value of pretransplant splenectomy in patients with myelofibrosis (MF) is subject to debate, since the procedure may preclude subsequent allogeneic hematopoietic cell transplantation (allo-HCT). To determine the impact of pretransplant splenectomy on the incidence of allo-HCT, we conducted a comprehensive retrospective study of all patients with MF for whom an unrelated donor search had been initiated via the French bone marrow transplantation registry (RFGM) between 1 January 2008 and 1 January 2017. Additional data were collected from the patients' medical files and a database held by the French-Language Society for Bone Marrow Transplantation and Cell Therapy (SFGM-TC). We used a multistate model with four states ("RFGM registration"; "splenectomy"; "death before allo-HCT", and "allo-HCT") to evaluate the association between splenectomy and the incidence of allo-HCT. The study included 530 patients from 57 centers. With a median follow-up time of 6 years, we observed 81 splenectomies, 99 deaths before allo-HCT (90 without splenectomy and nine after), and 333 allo-HCTs (268 without splenectomy and 65 after). In a bivariable analysis, the hazard ratio [95% confidence interval (CI)] for the association of splenectomy with allo-HCT was 7.2 [5.1-10.3] in the first 4 months and 1.18 [0.69-2.03] thereafter. The hazard ratio [95% CI] for death associated with splenectomy was 1.58 [0.79-3.14]. These reassuring results suggest that splenectomy does not preclude allo-HCT in patients with MF.

Primary myelofibrosis: 2021 update on diagnosis, risk-stratification and management

DISEASE OVERVIEW

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm (MPN) characterized by stem cell-derived clonal myeloproliferation that is often but not always accompanied by JAK2, CALR, or MPL mutations. Additional disease features include bone marrow reticulin/collagen fibrosis, aberrant inflammatory cytokine expression, anemia, hepatosplenomegaly, extramedullary hematopoiesis (EMH), constitutional symptoms, cachexia, leukemic progression, and shortened survival.

DIAGNOSIS

Bone marrow morphology is the primary basis for diagnosis. Presence of JAK2, CALR, or MPL mutation, expected in around 90% of the patients, is supportive but not essential for diagnosis; these mutations are also prevalent in the closely related MPNs, namely polycythemia vera (PV) and essential thrombocythemia (ET). The 2016 World Health Organization classification system distinguishes "prefibrotic" from "overtly fibrotic" PMF; the former might mimic ET in its presentation. Furthermore, approximately 15% of patients with ET or PV might progress into a PMF-like phenotype (post-ET/PV MF) during their clinical course.

ADVERSE MUTATIONS

SRSF2, ASXL1, and U2AF1-Q157 mutations predict inferior survival in PMF, independent of each other and other risk factors. RAS/CBL mutations predicted resistance to ruxolitinib therapy.

ADVERSE KARYOTYPE

Very high risk abnormalities include -7, inv (3), i(17q), +21, +19, 12p-, and 11q-.

RISK STRATIFICATION

Two new prognostic systems for PMF have recently been introduced: GIPSS (genetically-inspired prognostic scoring system) and MIPSS70+ version 2.0 (MIPSSv2; mutation- and karyotype-enhanced international prognostic scoring system). GIPSS is based exclusively on mutations and karyotype. MIPSSv2 includes, in addition, clinical risk factors. GIPSS features four and MIPSSv2 five risk categories.

RISK-ADAPTED THERAPY

Observation alone is advised for MIPSSv2 "low" and "very low" risk disease (estimated 10-year survival 56%-92%); allogeneic hematopoietic stem cell transplant (AHSCT) is the preferred treatment for "very high" and "high" risk disease (estimated 10-year survival 0%-13%); treatment-requiring patients with intermediate-risk disease (estimated 10-year survival 30%) are best served by participating in clinical trials. In non-transplant candidates, conventional treatment for anemia includes androgens, prednisone, thalidomide, and danazol; for symptomatic splenomegaly, hydroxyurea and ruxolitinib; and for constitutional symptoms, ruxolitinib. Fedratinib, another JAK2 inhibitor, has now been FDA-approved for use in ruxolitinib failures. Splenectomy is considered for drug-refractory splenomegaly and involved field radiotherapy for non-hepatosplenic EMH and extremity bone pain.

NEW DIRECTIONS

A number of new agents, alone or in combination with ruxolitinib, are currently under investigation for MF treatment (ClinicalTrials.gov); preliminary results from some of these clinical trials were presented at the 2020 ASH annual meeting and highlighted in the current document.

Management of challenging myelofibrosis after JAK inhibitor failure and/or progression

The myeloproliferative neoplasms (MPNs) encompass a heterogenous set of diseases that have variable survival, but in the setting of treatment refractory and progressive disease, prognosis has been characteristically poor. JAK inhibition with ruxolitinib or fedratinib therapy has become the first line treatment for symptomatic or intermediate to high risk myelofibrosis. However, after three years of ruxolitinib therapy, approximately half of all patients with myelofibrosis will likely have stopped treatment. JAK inhibition failure represents a mixture of etiologies, including drug intolerance, suboptimal dosing, drug resistance, or progression of disease. JAK inhibition failure and accelerated/blast phase have now become the primary clinical challenges in the treatment of myelofibrosis and high risk polycythemia vera, and no phase III trials or clear treatment guidelines exist to guide management strategies in this setting. On the other hand, this represents an exciting time in treatment of JAK inhibitor failure and accelerated phase MPNs due to the advent of recently approved drugs as well as new targeted agents currently under investigation. In this article, we review the management options for these challenging clinical scenarios. We discuss the options for JAK inhibitor dose optimization and overcoming resistance by utilizing combinations of JAK inhibition, primarily ruxolitinib, with alternative commercially available therapies. For patients who have progressed, we discuss recent data regarding targeted therapy options approved for AML that represent potentially efficacious options in the progressive MPN setting. We also discuss the new clinical agents under development in MF and accelerated MPNs that may offer new therapeutic options in the years to come.

Splenectomy in Myelofibrosis: Indications, Efficacy, and Complications

Splenomegaly, which may range from a few centimeters below the left costal border to massive dimensions, is one of the most characteristic features in patients with advanced myelofibrosis (MF). Splenectomy may offer an effective therapeutic option for treating massive splenomegaly in patients with MF, and especially in cases of disease refractory to conventional drugs, but it is associated with a number of complications as well as substantial morbidity and mortality. Whether splenectomy should be performed before allogeneic hematopoietic stem-cell transplantation is also controversial, and there is a lack of prospective randomized clinical trials that assess the role of splenectomy before hematopoietic stem-cell transplantation in patients with MF. Although splenectomy is not routinely performed before transplantation, it may be appropriate in patients with massive splenomegaly and related symptoms, so long as the higher risk of graft failure in such cases is taken into account. This review aims to describe the efficacy, indications, and complications of splenectomy in patients with MF; and to evaluate the long-term impact of splenectomy on patient survival and risk of disease transformation.

Patterns of Ruxolitinib Therapy Failure and Its Management in Myelofibrosis: Perspectives of the Canadian Myeloproliferative Neoplasm Group

Ruxolitinib improves splenomegaly and other disease-related symptoms in patients with myelofibrosis, but over time, many patients lose this benefit. It is difficult to determine whether this is due to resistance or intolerance to the drug; thus, we have used the more inclusive term of ruxolitinib failure. The survival of patients with myelofibrosis after ruxolitinib failure is poor but varies significantly by the pattern of the failure, underlining the need for a clinically appropriate classification. In this review, we propose diagnostic guidance for early recognition of the pattern of ruxolitinib failure and we recommend treatment options. The most frequent patterns of ruxolitinib failure are loss or failure to obtain a significant reduction in splenomegaly or symptom response, and the development or persistence of clinically significant cytopenias. Ruxolitinib dose modification and other ancillary therapies are sometimes helpful, and splenectomy is a palliative option in selected cases. Stem-cell transplantation is the only curative option for these patterns of failure, but its restricted applicability due to toxicity highlights the importance of ongoing clinical trials in this area. Recent approval of fedratinib by the US Food and Drug Administration provides an alternative option for patients with suboptimal or loss of spleen response. The transformation of myelofibrosis to accelerated or blast phase is an infrequent form of failure with an extremely poor prognosis, whereby patients who are ineligible for transplantation have limited treatment options.

Extramedullary blastic transformation of primary myelofibrosis in the form of disseminated myeloid sarcoma: a case report and review of the literature

Splenomegaly is a key clinical manifestation of myelofibrosis, and splenectomy is currently indicated in patients with drug refractory, symptomatic splenomegaly or with the aim of improving refractory cytopenias. Transformation to acute myeloid leukemia occurs in up to 20% of patients with myelofibrosis, while cases of myeloid sarcoma have been reported very unfrequently. In this manuscript, we report the case of a 60-year-old man with a history of primary myelofibrosis who underwent splenectomy because of drug-refractory massive splenomegaly, systemic symptoms and anemia. At the opening of the peritoneal cavity, the spleen resulted massively enlarged and tenaciously entrapped by a pervasive neoplastic-like tissue. The extensive involvement of the abdomen fatally complicated the surgical procedure. At postmortem examination, the spleen showed a diffuse infiltration of immature cells that were also found in the peritoneum, bowel, liver, lungs and myocardium. After immunohistochemical, cytogenetic, flow cytometric and molecular characterization of neoplastic population, a diagnosis of disseminated myeloid sarcoma of the spleen was made. This case report highlights a very unusual case of myeloid sarcoma originating from the spleen in a patient with myelofibrosis who had no evidence of bone marrow or peripheral blood involvement by leukemic cells. Molecular characterization showed that leukemic cells originated from the founding clone of the chronic phase. The sarcoma could not be suspected based on clinical findings and was diagnosed only at the time of surgical procedure and autopsy. This case suggests that leukemic transformation of myelofibrosis can originate outside the bone marrow and, presumably rarely, present as a granulocytic sarcoma.

Primary myelofibrosis: 2019 update on diagnosis, risk-stratification and management

DISEASE OVERVIEW

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm (MPN) characterized by stem cell-derived clonal myeloproliferation that is often but not always accompanied by JAK2, CALR, or MPL mutations; additional disease features include bone marrow stromal reaction including reticulin fibrosis, abnormal cytokine expression, anemia, hepatosplenomegaly, extramedullary hematopoiesis (EMH), constitutional symptoms, cachexia, leukemic progression, and shortened survival.

DIAGNOSIS

Diagnosis of PMF is based on bone marrow morphology. Presence of JAK2, CALR, or MPL mutation, expected in ∼ 90% of the patients, is supportive but not essential for diagnosis. The revised 2016 World Health Organization (WHO) classification system distinguishes "prefibrotic" from "overtly fibrotic" PMF; the former might mimic ET in its presentation and it is prognostically relevant to distinguish the two.

RISK STRATIFICATION

Two new prognostic systems for PMF have recently been introduced: GIPSS (genetically inspired prognostic scoring system) and MIPSS70+ version 2.0 (mutation- and karyotype-enhanced international prognostic scoring system). GIPSS is based exclusively on mutations and karyotype. MIPSS70+ version 2.0 utilizes both genetic and clinical risk factors. GIPSS features four and MIPSS70+ version 2.0 five risk categories. MIPSS70+ version 2.0 requires an online score calculator (http://www.mipss70score.it) while GIPPS offers a lower complexity prognostic tool.

RISK-ADAPTED THERAPY

Observation alone is advised for MIPSS70+ version 2.0 "low" and "very low" risk disease (estimated 10-year survival 56%-92%); allogeneic stem cell transplant is the preferred treatment of choice for "very high" and "high" risk disease (estimated 10-year survival 0-13%); treatment-requiring patients with intermediate-risk disease (estimated 10-year survival 30%) are best served by participating in clinical trials. All other treatment approaches, including the use of JAK2 inhibitors, are mostly palliative and should not be used in the absence of clear treatment indications. Conventional treatment for anemia includes androgens, prednisone, thalidomide and danazol, for symptomatic splenomegaly hydroxyurea and ruxolitinib and for constitutional symptoms ruxolitinib. Splenectomy is considered for drug-refractory splenomegaly and involved field radiotherapy for nonhepatosplenic EMH and extremity bone pain.

Splenectomy in patients with chronic myelomonocytic leukemia: Indications, histopathological findings and clinical outcomes in a single institutional series of thirty-nine patients

In a 28-year period, 39 (7%) patients with chronic myelomonocytic leukemia (CMML) (median age 66 years, 64% male) underwent a splenectomy at our institution. Primary indications for splenectomy were refractory thrombocytopenia (36%), progressive spleen related symptoms (33%), emergent splenectomy for splenic rupture (21%), refractory anemia (8%), and prior to allogeneic stem cell transplant (3%). Eleven (28%) patients had anemia at the time of splenectomy, of which 3 (27%) were autoimmune. The median time to splenectomy from CMML diagnosis was 6 months (0-40); perioperative morbidity and mortality rates were 43% and 13%, while the median postsplenectomy survival was 25 months (11-38). Durable remission in spleen related symptoms, thrombocytopenia, complications from splenic rupture, and anemia were achieved in 85%, 50%, 62%, and 21% of patients, respectively. Perioperative morbidity (n = 30) included infections/sepsis in 6 (20%), intraabdominal bleeding in 4 (13%), venous thromboembolism (VTE) in 3 (10%), and acute lung injury in 2 (7%) patients. The median duration of hospital stay was 6 days (1-25), with 5 deaths occurring secondary to respiratory failure (n = 2), multiorgan dysfunction (n = 2) and hemorrhagic shock (n = 1). There was no difference in overall survival between CMML patients that underwent splenectomy, in comparison to those that did not. Unlike in myelofibrosis, portal hypertension was not an indication for splenectomy and no patients developed post-splenectomy thrombocytosis. In conclusion, apart from being a lifesaving emergent modality in the event of splenic rupture, splenectomy has an important palliative role in patients with CMML, with significant and durable improvements in spleen related symptoms and refractory cytopenias.

Myelofibrosis Treatment Algorithm 2018

Two novel prognostic systems for primary myelofibrosis (PMF) were recently unveiled: GIPSS (genetically inspired prognostic scoring system) and MIPSS70 (mutation-enhanced international prognostic scoring system for transplant-age patients). GIPSS is based exclusively on genetic markers: mutations and karyotype. MIPSS70 includes mutations and clinical risk factors. In its most recent adaptation, the prognostic value of MIPSS70 has been bolstered by the inclusion of a three-tiered cytogenetic risk stratification and use of hemoglobin thresholds that are adjusted for sex and severity (MIPSS70+ version 2.0). GIPSS features four, MIPSS70 three, and MIPSS70+ version 2.0 five risk categories. MIPSS70 is most useful in the absence of cytogenetic information. MIPSS70+ version 2.0 is more comprehensive than MIPSS70 and is the preferred model in the presence of cytogenetic information. Both MIPSS70 and MIPSS70+ version 2.0 require an online score calculator (http://www.mipss70score.it). GIPPS offers a lower complexity prognostic tool that reliably identifies candidates for allogeneic stem cell transplant (GIPSS high-risk disease) or long-term observation with little or no therapeutic intervention (GIPSS low-risk disease). Ultimately, we favor a step-wise prognostication approach that starts with GIPSS but also considers MIPSS70+ version 2.0 for confirming the most appropriate treatment approach for the individual patient.

How I treat myelofibrosis after failure of JAK inhibitors

The introduction of JAK inhibitors, leading to regulatory approval of ruxolitinib, represents a major therapeutic advance in myelofibrosis (MF). Most patients experience reduction in splenomegaly and improved quality of life from symptom improvement. It is a paradox, however, that, despite inhibition of signaling downstream of disease-related driver mutations, JAK inhibitor treatment is not associated with consistent molecular or pathologic responses in MF. Furthermore, there are important limitations to JAK inhibitor therapy including development of dose-limiting cytopenias and/or nonhematological toxicities such as neuropathy or opportunistic infections. Over half of the patients discontinue treatment within 3 years of starting treatment. Although data are sparse, clinical outcome after JAK inhibitor "failure" is likely poor; consequently, it is important to understand patterns of failure to select appropriate salvage treatment(s). An algorithmic approach, particularly one that incorporates cytogenetics/molecular data, is most helpful in selecting stem cell transplant candidates. Treatment of transplant-ineligible patients relies on a problem-based approach that includes use of investigational drugs, or consideration of splenectomy or radiotherapy. Data from early phase ruxolitinib combination studies, despite promising preclinical data, have not shown clear benefit over monotherapy thus far. Development of effective treatment strategies for MF patients failing JAK inhibitors remains a major unmet need.

Current approaches to challenging scenarios in myeloproliferative neoplasms

INTRODUCTION

The Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) including polycythemia vera, essential thrombocythemia and primary myelofibrosis are clonal hematological malignancies that originate at the level of the hematopoietic stem cell, and are characterized by excessive proliferation of cells belonging to one or more of the myeloid lineages. Central to the pathogenesis of the MPNs is constitutive activation of the JAK/STAT signaling pathway due to a family of driver mutations affecting JAK2, CALR or MPL. These disorders share common clinical and laboratory features, a significant burden of systemic symptoms, increased risk of developing arterial and venous thrombotic events, and the potential to progress to myelofibrosis and acute leukemia. Areas covered: We identified four clinical situations which represent challenging management dilemmas for patients with MPNs. Our conclusions and recommendations are based on a literature search using MEDLINE and recent meeting abstracts using the keywords, focusing on publications directly addressing these scenarios and on recent contributions to the field. Expert commentary: Multi-center efforts to study large cohorts of MPN patients have led to more uniform and evidence-based approaches to key aspects in MPN management. However, treatment strategies to deal with specific clinical scenarios are lacking.

Understanding Splenomegaly in Myelofibrosis: Association with Molecular Pathogenesis

Myelofibrosis (MF) is a clinical manifestation of chronic BCR-ABL1-negative chronic myeloproliferative neoplasms. Splenomegaly is one of the major clinical manifestations of MF and is directly linked to splenic extramedullary hematopoiesis (EMH). EMH is associated with abnormal trafficking patterns of clonal hematopoietic cells due to the dysregulated bone marrow (BM) microenvironment leading to progressive splenomegaly. Several recent data have emphasized the role of several cytokines for splenic EMH. Alteration of CXCL12/CXCR4 pathway could also lead to splenic EMH by migrated clonal hematopoietic cells from BM to the spleen. Moreover, low Gata1 expression was found to be significantly associated with the EMH. Several gene mutations were found to be associated with significant splenomegaly in MF. In recent data, JAK2V617F homozygous mutation was associated with a larger spleen size. In other data, CALR mutations in MF were signigicantly associated with longer larger splenomegaly-free survivals than others. In addition, MF patients with ≥1 mutations in AZXL1, EZH1 or IDH1/2 had significantly low spleen reduction response in ruxolitinib treatment. Developments of JAK inhibitors, such as ruxolitinib, pacritinib, momelotinib, and febratinib enabled the effective management in MF patients. Especially, significant spleen reduction responses of the drugs were demonstrated in several randomized clinical studies, although those could not eradicate allele burdens of MF.