Allogeneic stem cell transplantation after reduced-intensity conditioning in patients with myelofibrosis: a prospective, multicenter study of the Chronic Leukemia Working Party of the European Group for Blood and Marrow Transplantation

Therapeutic approaches in myelofibrosis and myelodysplastic/myeloproliferative overlap syndromes

The discovery of JAK2 (V617F) a decade ago led to optimism for a rapidly developing treatment revolution in Ph(-) myeloproliferative neoplasms. Unlike BCR-ABL, however, JAK2 was found to have a more heterogeneous role in carcinogenesis. Therefore, for years, development of new therapies was slow, despite standard treatment options that did not address the overwhelming symptom burden in patients with primary myelofibrosis (MF), post-essential thrombocythemia MF, post-polycythemia vera MF, and myelodysplastic syndrome (MDS)/myeloproliferative neoplasm (MPN) syndromes. JAK-STAT inhibitors have changed this, drastically ameliorating symptoms and ultimately beginning to show evidence of impact on survival. Now, the genetic foundations of myelofibrosis and MDS/MPN are rapidly being elucidated and contributing to targeted therapy development. This has been empowered through updated response criteria for MDS/MPN and refined prognostic scoring systems in these diseases. The aim of this article is to summarize concisely the current and rationally designed investigational therapeutics directed at JAK-STAT, hedgehog, PI3K-Akt, bone marrow fibrosis, telomerase, and rogue epigenetic signaling. The revolution in immunotherapy and novel treatments aimed at previously untargeted signaling pathways provides hope for considerable advancement in therapy options for those with chronic myeloid disease.

Allogeneic hematopoietic cell transplantation in patients with myelofibrosis: A single center experience

Myelofibrosis (MF) is a rare disease responsible for an increasing ineffective hematopoesis by a progressive fibrosing process in the bone marrow. The only curative treatment option is allogeneic hematopoietic cell transplantation (HCT). In this single-center analysis, we evaluated retrospectively 54 consecutive patients suffering from primary or secondary MF which underwent HCT from 1997 to 2014 after either myeloablative (MAC, n = 19) or reduced-intensity conditioning (RIC, n = 35). Overall survival (OS) and disease-free survival (DFS) after 3 years was 54/53 % for RIC versus 63/58 % for MAC (p = 0.8/0.97). Cumulative incidence of relapse was 34 % after RIC and 8 % after MAC (p = 0.16). Three-year non-relapse mortality (NRM) was 15 % after RIC and 34 % after MAC (p = 0.29). We found that RIC was associated with a lower incidence of acute graft versus host disease (GvHD; II-IV 26 vs. 0 %, p = 0.004). Evaluation of prognostic relevance of the Dynamic International Prognostic Scoring System (DIPSS) score showed a significant better OS in patient with risk score ≤3 versus >3 (after 3 years, 71 vs. 39 %, p = 0.008). While similar OS and DFS were observed with MAC or RIC, the use of RIC resulted in lower incidence of acute GvHD. RIC regimens may be therefore the preferred conditioning approach for allogeneic HCT in patients with MF.

The indications for allogeneic stem cell transplantation in myeloid malignancies

BACKGROUND

The overall incidence of myeloid malignancies is 8.6 per 100 000 persons. Allogeneic stem-cell transplantation (SCT) is a major therapeutic option despite its risks, which include graft-versus-host disease (GvHD) and infection. In Germany, about 1600 patients with myeloid malignancies undergo SCT each year. The indications for SCT have changed since the introduction of tyrosine kinase inhibitors (TKI) and improved methods of SCT.

METHODS

This article is based on relevant guidelines from Germany and abroad and on a selective review of the literature from 2010 onward.

RESULTS

The individual indication for SCT is based on the risk of disease progression, accompanying illnesses, the probability that SCT will result in cure, and the risk of complications. There is good evidence favoring allogeneic SCT in the following situations affecting 20% to 50% of patients with the respective disease: advanced chronic myeloid leukemia (CML) or CML that does not respond to TKI, Philadelphia chromosome-negative myeloproliferative neoplasm (Ph- MPN) or myelodysplastic syndrome (MDS) with a high risk of progression, and acute myeloid leukemia (AML) that has high-risk cytogenetic features or is recurrent. Good evidence is accumulating in favor of allogeneic SCT in older patients as well.

CONCLUSION

The prognosis of patients with myeloid neoplasm can now be assessed more accurately than before. This facilitates well-founded clinical decision-making about SCT, which is the only potentially curative treatment for most patients with myeloid neoplasm. Patients up to about age 75 should be referred to a transplantation center for consultation at an early stage of their disease so that the treatment options can be evaluated. A major goal of current research is to reduce toxicity with innovative forms of treatment.

Outcome after Transplantation According to Reduced-Intensity Conditioning Regimen in Patients Undergoing Transplantation for Myelofibrosis

Allogeneic hematopoietic stem cell transplantation remains the sole curative option for myelofibrosis. Many transplantation recipients receive a reduced-intensity conditioning (RIC) regimen owing to age or comorbidities; however, there is little published evidence to guide the choice of RIC regimen. In this study, we compared outcomes in patients who received 1 of 2 frequently used RIC regimens for patients with myelofibrosis: fludarabine-busulfan (FB) and fludarabine-melphalan (FM). A total of 160 patients underwent a RIC allograft procedure (FB group, n = 105; FM group, n = 55). We have developed a complex statistical model involving weighting and adjustment to permit comparison between these 2 groups. After weighting, the incidence of acute graft-versus-host disease (GVHD) was 62% in the FM group and 31% in the FB group (P = .001), and the corresponding incidence of chronic GVHD was 49% and 53%, respectively. The 7-year progression-free survival was were 52% in the FM group versus 33% in the FB group, and the 7-year overall survival rate 52% in the FM group versus 59% in the FB group. Nonrelapse mortality (NRM) was 43% in the FM group and 31% in the FB group. Multivariable analyses revealed no significant differences in PFS between the 2 groups; however, the relapse rate was significantly lower in the FM group (hazard ratio, 9.21; P = .008), whereas a trend toward reduced NRM was seen in the FB group (hazard ratio, 0.51; P = .068). In conclusion, both regimens appear to be efficient in mediating disease control and can be used to successfully condition patients with myelofibrosis. The FM regimen appears to induce more NRM than the FB regimen, but with augmented control of disease, leading to comparable overall survival rates for both regimens.

New Strategies in Myeloproliferative Neoplasms: The Evolving Genetic and Therapeutic Landscape

The classical BCR-ABL1-negative myeloproliferative neoplasms (MPN) include essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF). Although these clonal disorders share certain clinical and genetic features, MF in particular is distinct for its complex mutational landscape, severe disease phenotype, and poor prognosis. The genetic complexity inherent to MF has made this disease extremely challenging to treat. Pharmacologic JAK inhibition has proven to be a transformative therapy in MPNs, alleviating symptom burden and improving survival, but has been hampered by off-target toxicities and, as monotherapy, has shown limited effects on mutant allele burden. In this review, we discuss the genetic heterogeneity contributing to the pathogenesis of MPNs, focusing on novel driver and epigenetic mutations and how they relate to combination therapeutic strategies. We discuss results from ongoing studies of new JAK inhibitors and report on new drugs and drug combinations that have demonstrated success in early preclinical and clinical trials, including type II JAK inhibitors, antifibrotic agents, and telomerase inhibitors.

Myeloproliferative neoplasms and inflammation: whether to target the malignant clone or the inflammatory process or both

The Philadelphia-negative myeloproliferative neoplasms (MPNs) are clonal disorders involving hematopoietic stem and progenitor cells and are associated with myeloproliferation, splenomegaly and constitutional symptoms. Similar signs and symptoms can also be found in patients with chronic inflammatory diseases, and inflammatory processes have been found to play an important role in the pathogenesis and progression of MPNs. Signal transduction pathways involving JAK1, JAK2, STAT3 and STAT5 are causally involved in driving both the malignant cells and the inflammatory process. Moreover, anti-inflammatory and immune-modulating drugs have been used successfully in the treatment of MPNs. However, to date, many unresoved issues remain. These include the role of somatic mutations that are present in addition to JAK2V617F, CALR and MPL W515 mutations, the interdependency of malignant and nonmalignant cells and the means to eradicate MPN-initiating and -maintaining cells. It is imperative for successful therapeutic approaches to define whether the malignant clone or the inflammatory cells or both should be targeted. The present review will cover three aspects of the role of inflammation in MPNs: inflammatory states as important differential diagnoses in cases of suspected MPN (that is, in the absence of a clonal marker), the role of inflammation in MPN pathogenesis and progression and the use of anti-inflammatory drugs for MPNs. The findings emphasize the need to separate the inflammatory processes from the malignancy in order to improve our understanding of the pathogenesis, diagnosis and treatment of patients with Philadelphia-negative MPNs.

Evolving Therapeutic Strategies for the Classic Philadelphia-Negative Myeloproliferative Neoplasms

Despite the emergence of JAK inhibitors, there is a need for disease-modifying treatments for Philadelphia-negative myeloproliferative neoplasms (MPNs). JAK inhibitors ameliorate symptoms and address splenomegaly, but because of the heterogeneous contributors to the disease process, JAK inhibitor monotherapy incompletely addresses the burden of disease. The ever-growing understanding of MPN pathogenesis has provided the rationale for testing novel and targeted therapeutic agents, as monotherapies or in combination, in preclinical and clinical settings. A number of intriguing options have emerged, and it is hoped that further progress will lead to significant changes in the natural history of MPNs.

Allogeneic hematopoietic stem cell transplantation for myelofibrosis and chronic myelomonocytic leukemia

The efficacy of hematopoietic stem cell transplantation (HSCT) is not well established in Philadelphia chromosome negative myeloproliferative neoplasms (Ph- MPNs). Without randomized prospective trials comparing HSCT to non-HSCT options or comparing HSCT regimens, physicians must rely on prognostic scoring systems and clinical experience when making decisions about who and when to transplant patients with Ph- MPNs. These patients are vulnerable to hepatic toxicity and graft failure after HSCT because of their increased likelihood of portal hypertension, massive splenomegaly, and extensive bone marrow fibrosis related to their disease. In this review, we aim to outline the indications and modalities of HSCT as they pertain to the Ph- MPNs and CMML based on the currently available evidence. We will further highlight the challenges of HSCT in these diseases, including but not limited to the incorporation of JAK inhibitors into HSCT for myelofibrosis.

Cytokine Expression Pattern in Bone Marrow Microenvironment after Allogeneic Stem Cell Transplantation in Primary Myelofibrosis

The only curative therapy for primary myelofibrosis (PMF) is allogeneic stem cell transplantation (ASCT). However, although we know that patients can benefit from ASCT, we do not know the extent of the changes of the expression profile of cytokines and matrix modulation factors. In this first systematic analysis, we evaluated the expression profile of 103 factors before and after transplantation to identify potential biomarkers. The expression of fibrosis-, inflammation-, and angiogenesis-associated genes was analyzed in a total of 52 bone marrow biopsies: PMF patients (n = 14) before and after ASCT and, for control purposes, post-ASCT multiple myeloma patients (n = 14) and non-neoplastic hematopoiesis (n = 10). In post-ASCT PMF cases, decreased expression of tissue inhibitor of metalloproteinases (TIMP) and platelet-derived growth factor alpha (PDGFA) correlated with bone marrow remodeling and hematological remission. Expression of several other matrix factors remained at high levels and may contribute to post-ASCT remodeling. This is the first systematic analysis of cytokine expression in post-ASCT PMF bone marrow that shows that normalization of bone marrow microenvironment is paralleled by decreased expression of TIMP and PDGFA.

Myelofibrosis-When Do We Select Transplantation or Non-transplantation Therapeutic Options?

Janus kinase 1/2 (JAK1/2) inhibitor therapy is effective in alleviating myelofibrosis (MF)-related symptoms. However, at present, the only curative therapy for MF patients is hematopoietic cell transplantation (HCT). The decision of whether to proceed with HCT, which carries significant risks, or continue with JAK inhibitor therapy is a complicated one. Nevertheless, careful assessment of patient, disease, and transplant-related factors can guide this decision on a case-by-case basis. Difficult questions arise in the decision-making process such as age limits, whether lower-risk patients are suitable candidates, and HCT in patients responding well to JAK inhibitor therapy. The optimal timing of transplant is a major dilemma in the management of MF patients who are responding to or are stable on JAK inhibitor therapy. In this paper, we provide our perspective on selection of transplant versus non-transplant therapies in the management of MF.

Inflammation as a Keystone of Bone Marrow Stroma Alterations in Primary Myelofibrosis

Primary myelofibrosis (PMF) is a clonal myeloproliferative neoplasm where severity as well as treatment complexity is mainly attributed to a long lasting disease and presence of bone marrow stroma alterations as evidenced by myelofibrosis, neoangiogenesis, and osteosclerosis. While recent understanding of mutations role in hematopoietic cells provides an explanation for pathological myeloproliferation, functional involvement of stromal cells in the disease pathogenesis remains poorly understood. The current dogma is that stromal changes are secondary to the cytokine “storm” produced by the hematopoietic clone cells. However, despite therapies targeting the myeloproliferation-sustaining clones, PMF is still regarded as an incurable disease except for patients, who are successful recipients of allogeneic stem cell transplantation. Although the clinical benefits of these inhibitors have been correlated with a marked reduction in serum proinflammatory cytokines produced by the hematopoietic clones, further demonstrating the importance of inflammation in the pathological process, these treatments do not address the role of the altered bone marrow stroma in the pathological process. In this review, we propose hypotheses suggesting that the stroma is inflammatory-imprinted by clonal hematopoietic cells up to a point where it becomes “independent” of hematopoietic cell stimulation, resulting in an inflammatory vicious circle requiring combined stroma targeted therapies.

Outcomes of Allogeneic Hematopoietic Cell Transplantation in Patients with Myelofibrosis with Prior Exposure to Janus Kinase 1/2 Inhibitors

The impact of Janus kinase (JAK) 1/2 inhibitor therapy before allogeneic hematopoietic cell transplantation (HCT) has not been studied in a large cohort in myelofibrosis (MF). In this retrospective multicenter study, we analyzed outcomes of patients who underwent HCT for MF with prior exposure to JAK1/2 inhibitors. One hundred consecutive patients from participating centers were analyzed, and based on clinical status and response to JAK1/2 inhibitors at the time of HCT, patients were stratified into 5 groups: (1) clinical improvement (n = 23), (2) stable disease (n = 31), (3) new cytopenia/increasing blasts/intolerance (n = 15), (4) progressive disease: splenomegaly (n = 18), and (5) progressive disease: leukemic transformation (LT) (n = 13). Overall survival (OS) at 2 years was 61% (95% confidence interval [CI], 49% to 71%). OS was 91% (95% CI, 69% to 98%) for those who experienced clinical improvement and 32% (95% CI, 8% to 59%) for those who developed LT on JAK1/2 inhibitors. In multivariable analysis, response to JAK1/2 inhibitors (P = .03), dynamic international prognostic scoring system score (P = .003), and donor type (P = .006) were independent predictors of survival. Among the 66 patients who remained on JAK1/2 inhibitors until stopped for HCT, 2 patients developed serious adverse events necessitating delay of HCT and another 8 patients had symptoms with lesser severity. Adverse events were more common in patients who started tapering or abruptly stopped their regular dose ≥6 days before conditioning therapy. We conclude that prior exposure to JAK1/2 inhibitors did not adversely affect post-transplantation outcomes. Our data suggest that JAK1/2 inhibitors should be continued near to the start of conditioning therapy. The favorable outcomes of patients who experienced clinical improvement with JAK1/2 inhibitor therapy before HCT were particularly encouraging, and need further prospective validation.

Improved Outcome of Alternative Donor Transplantations in Patients with Myelofibrosis: From Unrelated to Haploidentical Family Donors

This is a retrospective analysis of 95 patients with myelofibrosis who were allografted between 2001 and 2014. The aims of the study were to assess whether the outcome of alternative donor grafts has improved with time and how this compares with the outcome of identical sibling grafts. Patients were studied in 2 time intervals: 2000 to 2010 (n = 58) and 2011 to 2014 (n = 37). The Dynamic International Prognostic Scoring System score was comparable in the 2 time periods, but differences in the most recent group included older age (58 versus 53 years, P = .004), more family haploidentical donors (54% versus 5%, P < .0001), and the introduction of the thiotepa-fludarabine-busulfan conditioning regimen (70% of patients versus 2%, P < .0001). Acute and chronic graft-versus-host disease were comparable in the 2 time periods. The 3-year transplantation-related mortality (TRM) in the 2011 to 2014 period versus the 2000 to 2010 period is 16% versus 32% (P = .10), the relapse rate 16% versus 40% (P = .06), and actuarial survival 70% versus 39% (P = .08). Improved survival was most pronounced in alternative donor grafts (69% versus 21%, P = .02), compared with matched sibling grafts (72% versus 45%, P = .40). In conclusion, the outcome of allografts in patients with myelofibrosis has improved in recent years because of a reduction of both TRM and relapse. Improvement is most significant in alternative donor transplantations, with modifications in donor type and conditioning regimen.

Hematopoietic Cell Transplantation as Curative Therapy for Patients with Myelofibrosis: Long-Term Success in all Age Groups

Myeloproliferative neoplasms (MPN) are chronic marrow disorders with variable prognoses. Most patients with polycythemia vera, essential thrombocythemia, or even primary myelofibrosis (PMF) are successfully treated with conservative strategies for years or even decades, and recent data suggest that even in patients with high-risk disease, in particular those with PMF, life expectancy can be extended by treatment with janus kinase (JAK2) inhibitors. However, none of those modalities are curative, and after marrow failure develops, the disease "accelerates," or transforms to acute leukemia, the only option able to effectively treat and, in fact, cure MPN is allogeneic hematopoietic cell transplantation (HCT). Outcome is superior if HCT is performed before leukemic transformation occurs. Several reports document survival in unmaintained remission beyond 10 years. The most recent analyses show reduced regimen-related mortality (less than 10% or even 5% at day 100) and progressively improved survival with both HLA-identical sibling and unrelated donors. The development of low/reduced-intensity conditioning regimens has contributed to the improved success rate and has allowed successful HCT in patients in their seventh and even eighth decade of life. We propose, therefore, that HCT should be offered to fit patients in these age groups and should be covered by their respective insurance carriers.

Effect of treatment with a JAK2-selective inhibitor, fedratinib, on bone marrow fibrosis in patients with myelofibrosis

Background

Progressive bone marrow fibrosis (BMF) is a cardinal feature of many myeloproliferative neoplasms (MPNs) and there is a documented association between the severity of BMF and overall prognosis. We conducted an exploratory analysis of sequential BMF data from two phase I studies of long-term treatment with the Janus kinase 2 (JAK2) inhibitor fedratinib in patients with myelofibrosis.

Methods

Bone marrow samples were obtained at baseline and after every six cycles (24 weeks) of daily fedratinib treatment. Fibrosis was centrally assessed by three independent haematopathologists, who were blinded to the patients’ data, and graded according to European Consensus Myelofibrosis Grading Criteria. The analysis population comprised patients with a baseline BMF grade ≥1, and at least one post-baseline BMF grade assessment. Changes in BMF grade compared with baseline were classified as improvement (≥1 grade reduction), stabilisation (no change in any baseline BMF grade <3) or worsening (≥1 grade increase).

Results

Twenty-one patients were included in the analysis. A total of 153 bone marrow samples were analysed. Improvement or stabilisation of BMF from baseline was recorded in 15 of 18 (83 %) evaluable patients at cycle 6 and in four of nine (44 %) evaluable patients at cycle 30. Two patients achieved resolution of their BMF (grade = 0) by cycle 12.

Conclusions

This exploratory analysis indicates that improvement or even resolution of BMF may be achievable with JAK2 inhibitor therapy in some patients with MPNs and myelofibrosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0644-4) contains supplementary material, which is available to authorized users.

Janus Kinase Inhibitors and Stem Cell Transplantation in Myelofibrosis

Myelofibrosis (MF) is characterized by splenomegaly, blood count abnormalities, particularly cytopenias, and a propensity for transformation to acute leukemia. The current treatment approach is to ameliorate symptoms due to these abnormalities. Treatment with Janus kinase 2 inhibitors reduces spleen size and improves symptoms in patients with MF, but most of the patients eventually have disease progression and stop responding. Allogeneic stem cell transplantation remains the only curative option. However, its efficacy must be balanced against the risk of treatment-related death and long-term sequelae of transplant like chronic graft versus host disease. The challenge is to integrate treatment with Janus kinase inhibitors with allogeneic stem cell transplantation.

Indication and management of allogeneic stem cell transplantation in primary myelofibrosis: a consensus process by an EBMT/ELN international working group

The aim of this work is to produce recommendations on the management of allogeneic stem cell transplantation (allo-SCT) in primary myelofibrosis (PMF). A comprehensive systematic review of articles released from 1999 to 2015 (January) was used as a source of scientific evidence. Recommendations were produced using a Delphi process involving a panel of 23 experts appointed by the European LeukemiaNet and European Blood and Marrow Transplantation Group. Key questions included patient selection, donor selection, pre-transplant management, conditioning regimen, post-transplant management, prevention and management of relapse after transplant. Patients with intermediate-2- or high-risk disease and age <70 years should be considered as candidates for allo-SCT. Patients with intermediate-1-risk disease and age <65 years should be considered as candidates if they present with either refractory, transfusion-dependent anemia, or a percentage of blasts in peripheral blood (PB) >2%, or adverse cytogenetics. Pre-transplant splenectomy should be decided on a case by case basis. Patients with intermediate-2- or high-risk disease lacking an human leukocyte antigen (HLA)-matched sibling or unrelated donor, should be enrolled in a protocol using HLA non-identical donors. PB was considered the most appropriate source of hematopoietic stem cells for HLA-matched sibling and unrelated donor transplants. The optimal intensity of the conditioning regimen still needs to be defined. Strategies such as discontinuation of immune-suppressive drugs, donor lymphocyte infusion or both were deemed appropriate to avoid clinical relapse. In conclusion, we provided consensus-based recommendations aimed to optimize allo-SCT in PMF. Unmet clinical needs were highlighted.

Allogeneic stem cell transplant vs.Janus kinase inhibition in the treatment of primary myelofibrosis or myelofibrosis after essential thrombocythemia or polycythemia vera

Primary myelofibrosis is one of the Philadelphia chromosome-negative myeloproliferative neoplasms and is the member of that group with the worst survival and the most significant limitations in quality of life. Hepatosplenomegaly due to extramedullary hematopoiesis, constitutional symptoms, and cytopenias are the main manifestations. The natural history is highly variable, and up to 30% of patients can experience acceleration to acute myelogenous leukemia. Conventional therapy is only palliative and not always effective. However, huge advances have been achieved in the past 2 decades toward a better understanding of the pathogenesis of this disease, as well as improved management. Powerful risk stratification systems are now available and can reliably separate the patients into different prognostic categories to aid clinical management. Allogeneic stem cell transplant can offer cure but is still not universally applicable owing to the treatment-related mortality and toxicity. Nevertheless, outcomes of transplant are improving, owing to the introduction of reduced-intensity conditioning regimens and the optimization of remission monitoring techniques and relapse prevention strategies. The discovery of the V617F mutation of JAK2 (Janus kinase 2) and some other molecular aberrations has shed more light on the molecular pathogenesis of the disease and has led to the introduction of novel therapies such as JAK2 inhibitors. In fact, JAK inhibitors have shown promising symptomatic efficacy, and the JAK inhibitor ruxolitinib has also shown a potential survival benefit. Future effort should be made to combine allogeneic stem cell transplant with JAK inhibition.

Evading Capture by Residual Disease Monitoring: Extramedullary Manifestation of JAK2 V617F-Positive Primary Myelofibrosis After Allogeneic Stem Cell Transplantation

Monitoring of the JAK2 V617F allele burden in myeloproliferative neoplasms after allogeneic stem cell transplantation is useful to determine levels of residual disease and has the potential to detect early relapse and guide subsequent clinical intervention. A case is described of a JAK2 V617F-positive primary myelofibrosis patient who underwent allogeneic stem cell transplantation. Prospective residual disease monitoring of the peripheral blood failed to detect an extramedullary manifestation of the disease, a periorbital myeloid sarcoma, arising nearly three years after transplant. This case serves to highlight a pitfall in residual disease monitoring for myeloproliferative neoplasm-associated mutations in the post-allogeneic stem cell transplantation setting.

Effect of conditioning regimens on graft failure in myelofibrosis: a retrospective analysis

In myelofibrosis, the introduction of reduced-intensity conditioning (RIC) preceding allogeneic stem cell transplantation (SCT) resulted in lower transplant-related mortality rates compared with myeloablative conditioning. However, lowering the intensity of conditioning may increase the risk of graft failure in myelofibrosis, although hitherto this has not been indisputably proven. We here report the outcome of 53 patients who underwent allogeneic SCT with different conditioning regimens (RIC and non-myeloablative (NMA)) in three transplantation centers in the Netherlands. The cumulative incidence of graft failure within 60 days after SCT was high (28%), and this was primarily associated with the intensity of the conditioning regimen. Cumulative neutrophil engraftment at 60 days was lower in patients who received NMA conditioning compared with those who received RIC (56% vs 84%, P=0.03). Furthermore, of six patients who received a second transplantation after graft failure, the three patients with RIC regimens subsequently engrafted, whereas the three patients who received a second NMA regimen did not. This study indicates that in myelofibrosis, NMA regimens result in high engraftment failure rates. We propose the use of more intensive conditioning regimens, incorporating busulfan or melphalan.

Profile of pomalidomide and its potential in the treatment of myelofibrosis

Myelofibrosis, a Philadelphia-negative myeloproliferative neoplasm, is in a new treatment era after the discovery of the JAK2V617F mutation in 2005. JAK inhibitors boast improvements in disease-related symptoms, splenomegaly, and overall survival; however, treatment of myelofibrosis remains a challenge, given the lack of improvement in cytopenias with these agents. Second-generation immunomodulatory agents, such as pomalidomide, have shown efficacy in myelofibrosis-associated anemia within multiple clinical trials. Five major pomalido-mide clinical trials have been completed to date, and demonstrate tolerability and efficacy with low-dose pomalidomide (0.5 mg/day) in the treatment of myelofibrosis, and no clinical benefit of elevated dosing regimens (≥2.5 mg/day). Anemia responses ranged from 17% to 36% as per the International Working Group for Myelofibrosis Research and Treatment consensus guidelines, while improvements in splenomegaly were rare, and observed in <1% of most clinical trials. In comparison with earlier immunomodulatory agents, pomalidomide was associated with an improved toxicity profile, with substantially lower rates of myelosuppression and neuropathy. Given the low overall response rate to pomalidomide as a single agent, combination strategies are of particular interest for future studies. Pomalidomide is currently being tested in combination with ruxolitinib, and other novel combinations are likely on the horizon.

Myelofibrosis patients in Belgium: disease characteristics

OBJECTIVE

To date, only a small number of epidemiological studies on myelofibrosis have been performed. The current study aimed to characterize the myelofibrosis patient population in Belgium according to pre-defined disease parameters (diagnosis, risk categories, hemoglobin <10 g/dl, spleen size, constitutional symptoms, platelet count, myeloblast count), with a view to obtaining a deeper understanding of the proportion of patients that may benefit from the novel myelofibrosis therapeutic strategies.

METHODS

A survey was used to collect data on prevalence and disease parameters on all myelofibrosis patients seen at each of 18 participating hematologic centers in 2011. Aggregated data from all centers were used for analysis. Analyses were descriptive and quantitative.

RESULTS

A total of 250 patients with myelofibrosis were captured; of these, 136 (54%) were male and 153 (61%) were over 65 years old. One hundred sixty-five (66%) of myelofibrosis patients had primary myelofibrosis and 85 (34%) had secondary myelofibrosis. One hundred ninety-three myelofibrosis patients (77%) had a palpable spleen. About a third of patients (34%) suffered from constitutional symptoms. Two hundred twenty-two (89%) myelofibrosis patients had platelet count ≧50 000/μl and 201 (80%) had platelet count ≧100 000/μl. Of 250 patients, 85 (34%) had a myeloblast count ≧1%. Six (2%) patients had undergone a splenectomy. Thirteen (5·2%) patients had undergone radiotherapy for splenomegaly.

CONCLUSIONS

The results of this survey provide insight into the characteristics of the Belgian myelofibrosis population. They also suggest that a large proportion of these patients could stand to benefit from the therapies currently under development.

Indications for allo- and auto-SCT for haematological diseases, solid tumours and immune disorders: current practice in Europe, 2015

This is the sixth special report that the European Society for Blood and Marrow Transplantation regularly publishes on the current practice and indications for haematopoietic SCT for haematological diseases, solid tumours and immune disorders in Europe. Major changes have occurred in the field of haematopoietic SCT over the last years. Cord blood units as well as haploidentical donors have been increasingly used as stem cell sources for allo-SCT, thus, augmenting the possibility of finding a suitable donor for a patient. Continuous refinement of conditioning strategies has also expanded not only the number of potential indications but also has permitted consideration of older patients or those with co-morbidity for a transplant. There is accumulating evidence of the role of haematopoietic SCT in non-haematological disorders such as autoimmune diseases. On the other hand, the advent of new drugs and very effective targeted therapy has challenged the role of SCT in some instances or at least, modified its position in the treatment armamentarium of a given patient. An updated report with revised tables and operating definitions is presented.

Impact of allogeneic stem cell transplantation on survival of patients less than 65 years of age with primary myelofibrosis

Allogeneic hematopoietic stem cell transplantation (SCT) is the only curative option for patients with primary myelofibrosis (PMF), but information on its net advantage over conventional therapies is lacking. Using ad hoc statistical analysis, we determined outcomes in 438 patients <65 years old at diagnosis who received allogenic SCT (n = 190) or conventional therapies (n = 248). Among patients at low risk per the Dynamic International Prognostic Scoring System (DIPSS) model, the relative risk of death after allogenic SCT vs those treated with nontransplant modalities was 5.6 (95% CI, 1.7-19; P = .0051); for intermediate-1 risk it was 1.6 (95% CI, 0.79-3.2; P = .19), for intermediate-2 risk, 0.55 (95% CI, 0.36-0.83; P = .005), and for high risk, 0.37 (95% CI, 0.21-0.66; P = .0007). Thus, patients with intermediate-2 or high-risk PMF clearly benefit from allogenic SCT. Patients at low risk should receive nontransplant therapy, whereas individual counseling is indicated for patients at intermediate-1 risk.

Allo-SCT for myelofibrosis: reversing the chronic phase in the JAK inhibitor era?

At present, allo-SCT is the only curative treatment for patients with myelofibrosis (MF). Unfortunately, a significant proportion of candidate patients are considered transplant ineligible due to their poor general condition and advanced age at the time of diagnosis. The approval of the first JAK inhibitor, ruxolitinib, for patients with advanced MF in 2011 has had a qualified impact on the treatment algorithm. The drug affords substantial improvement in MF-associated symptoms and splenomegaly but no major effect on the natural history. There has, therefore, been considerable support for assessing the drug's candidacy in the peritransplant period. The drug's precise impact on clinical outcome following allo-SCT is currently not known; nor are the drug's long-term efficacy and safety known. Considering the rarity of MF and the small proportion of patients who undergo allo-SCT, well designed collaborative efforts are required. In order to address some of the principal challenges, an expert panel of laboratory and clinical experts in this field was established, and an independent workshop held during the 54th American Society of Hematology Annual Meeting in New Orleans, USA on 6 December 2013, and the European Hematology Association's Annual Meeting in Milan, Italy on 13 June 2014. This document summarizes the results of these efforts.

Assessment of bone marrow inflammation in patients with myelofibrosis: an 18F-fluorodeoxyglucose PET/CT study

PURPOSE

Myelofibrosis is a haematopoietic stem cell neoplasm characterized by bone marrow inflammation, reactive marrow fibrosis and extramedullary haematopoiesis. The aim of this study was to determine if (18)F-FDG PET/CT can be used to noninvasively visualize and quantify the extent and activity of bone marrow involvement.

METHODS

In 30 patients, the biodistribution of (18)F-FDG was analysed by measuring the standardized uptake value in the bone marrow compartment and spleen. Imaging findings were compared with laboratory, cytogenetic and histopathological data.

RESULTS

Retention of (18)F-FDG was observed in bone marrow and spleen. Bone marrow involvement varied, ranging from mildly increased uptake in the central skeleton to extensive uptake in most parts of the skeleton. The extent of bone marrow involvement decreased over time from initial diagnosis (r s  = -0.43, p = 0.019). Metabolic activity of the bone marrow decreased as the histopathological grade of fibrosis increased (r s  = -0.37, p = 0.04). There was a significant positive correlation between the metabolic activity of the bone marrow and that of the spleen (p = 0.04).

CONCLUSION

(18)F-FDG PET/CT is as a promising technique for the quantitation of bone marrow inflammation in myelofibrosis. Our data indicate that the intensity of bone marrow (18)F-FDG uptake decreases as bone marrow fibrosis increases. Further evaluation in prospective studies is required to determine the potential clinical impact and prognostic significance of PET.

Current therapies and their indications for the Philadelphia-negative myeloproliferative neoplasms

The groundbreaking discovery of the Janus-associated kinase 2 (JAK2) V617F mutation 10 years ago resulted in an unprecedented intensive basic and clinical research in Philadelphia-negative myeloproliferative neoplasms (MPNs). During these years, many new potential targets for therapy were identified that opened the era of targeted therapy for these diseases. However, only one new drug (ruxolitinib) has been approved during the past 40 years, and, although promising new therapies are evaluated, the armamentarium to treat MPN still relies on conventional drugs, like cytotoxic agents and anagrelide. The exact role of interferon (IFN) alfa still needs to be clarified in randomized studies, although it has been shown to be effective in MPNs for more than 25 years. The current therapeutic strategy for MPNs is based on the risk of vascular complication, which is the main cause of mortality and mortality in the medium term. However, the long-term outcome may be different, with an increasing risk of transformation to myelodysplastic syndrome or acute leukemia during follow-up times. Medicines able to change this natural history have not been clearly identified yet, and allogeneic stem cell transplantation currently remains the unique curative approach, which is only justified for patients with high-risk myelofibrosis or for patients with MPNs that have transformed to myelodysplasia or acute leukemia.

Treosulfan based reduced toxicity conditioning followed by allogeneic stem cell transplantation in patients with myelofibrosis

Allogeneic transplantation is the only potentially curative strategy for myelofibrosis, even in the era of new drugs that so far only mitigate symptoms. The choice to proceed to allogeneic transplantation is based on several variables including age, disease phase, degree of splenomegaly, donor availability, comorbidities and iron overload. These factors, along with conditioning regimen and time to transplantation, may influence the outcome of ASCT. We report 14 patients affected by myelofibrosis with a median age of 57 years (range, 41-76) receiving a treosulfan-fludarabine based reduced toxicity conditioning. Patients (pts) received a stem cell transplantation from an HLA identical (n = 10) or matched unrelated donor (n = 4). All pts had a complete myeloablation followed by engraftment and in 12 out of 13 evaluated pts donor chimerism was 100% at 1 month. In most cases a reduction of splenomegaly and a reduction (or resolution) of bone marrow fibrosis was observed. After a median follow-up of 39 months (range, 3-106), the 3-year probability of overall survival and disease free survival was 54 +/- 14% and 46 +/- 14%, respectively. The cumulative incidence of non-relapse mortality at 2 years was 39 +/- 15%. Causes of non-relapse mortality were: infection (n = 2), GvHD (n = 2) and haemorrhage (n = 1). We can conclude that a treosulfan and fludarabine based conditioning has a potent myeloablative and anti-disease activity although non-relapse mortality remains high in this challenging clinical setting. Copyright © 2014 John Wiley & Sons, Ltd.

Role of hematopoietic stem cell transplantation in patients with myeloproliferative disease

Myeloproliferative neoplasms (MPN) are clonal hematopoietic stem cell disorders. While some MPN patients have an indolent course, all are at risk of progressing to severe marrow failure or transforming into acute leukemia. Allogeneic hematopoietic cell transplantation (allo-HCT) is the only potential curative therapy. Major pre-transplant risk factors are disease stage of the MPN, the presence of comorbid conditions and the use of HLA non-identical donors. The development of reduced-intensity conditioning regimens has allowed for successful allo-HCT even for older patients and patients with comorbid conditions. The pre-transplant use of JAK2 inhibitors, which may be effective in down staging a patient's disease, may improve the outcomes following allo-HCT.

Controversies and dilemmas in allogeneic transplantation for myelofibrosis

JAK1/2 inhibitors have broadened the therapeutic options in myelofibrosis. Though not curative, they result in a meaningful clinical benefit with relatively fewer side effects. In contrast, allogeneic hematopoietic cell transplantation (HCT) is a potentially curative option, but is associated with significant morbidity and mortality. Hence, an important question is the optimal timing of HCT in the era of JAK inhibitors. Timing of HCT is a crucial decision, and need to be individualized based on the personal preferences and goals of therapy; in addition to patient, disease, and transplant related factors. Risk stratification by the currently established prognostic scoring systems need to be further refined by incorporation of prognostically significant mutations to guide the treatment choices better. Data on use of JAK inhibitors prior to HCT have just started to emerge. We discuss some of the current controversies and dilemmas in transplantation for myelofibrosis based on a few real life scenarios.

Primary myelofibrosis: 2014 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm characterized by stem cell-derived clonal myeloproliferation, abnormal cytokine expression, bone marrow fibrosis, anemia, splenomegaly, extramedullary hematopoiesis (EMH), constitutional symptoms, cachexia, leukemic progression, and shortened survival.

DIAGNOSIS

DIAGNOSIS is based on bone marrow morphology. The presence of JAK2, CALR, or MPL mutation is supportive but not essential for diagnosis; approximately 90% of patients carry one of these mutations and 10% are "triple-negative." None of these mutations are specific to PMF and are also seen in essential thrombocythemia (ET). Prefibrotic PMF mimics ET in its presentation and the distinction, enabled by careful bone marrow morphological examination, is prognostically relevant. Differential diagnosis also includes chronic myeloid leukemia, myelodysplastic syndromes, chronic myelomonocytic leukemia, and acute myeloid leukemia.

RISK STRATIFICATION

The Dynamic International Prognostic Scoring System-plus (DIPSS-plus) uses eight predictors of inferior survival: age >65 years, hemoglobin <10 g/dL, leukocytes >25 × 10(9) /L, circulating blasts ≥1%, constitutional symptoms, red cell transfusion dependency, platelet count <100 × 10(9) /L, and unfavorable karyotype (i.e., complex karyotype or sole or two abnormalities that include +8, -7/7q-, i(17q), inv(3), -5/5q-, 12p-, or 11q23 rearrangement). The presence of 0, 1, "2 or 3," and ≥4 adverse factors defines low, intermediate-1, intermediate-2, and high-risk disease with median survivals of approximately 15.4, 6.5, 2.9, and 1.3 years, respectively. High risk disease is also defined by CALR(-) /ASXL1(+) mutational status.

RISK-ADAPTED THERAPY

Observation alone is adequate for asymptomatic low/intermediate-1 risk disease, especially with CALR(+) /ASXL1(-) mutational status. Stem cell transplant is considered for DIPSS-plus high risk disease or any risk disease with CALR(-) /ASXL1(+) mutational status. Investigational drug therapy is reasonable for symptomatic intermediate-1 or intermediate-2 risk disease. Splenectomy is considered for drug-refractory splenomegaly. Involved field radiotherapy is most useful for post-splenectomy hepatomegaly, non-hepatosplenic EMH, PMF-associated pulmonary hypertension, and extremity bone pain.

Janus kinase inhibitors and allogeneic stem cell transplantation for myelofibrosis

Myelofibrosis (MF) is a manifestation of several disorders of hematopoiesis, collectively referred to as myeloproliferative neoplasms. Allogeneic hematopoietic stem cell transplantation (ASCT) is the only therapy with proven curative potential. However, most patients with MF are in their 6th or 7th decade of life, and only some of these patients have been considered suitable transplantation candidates. The development of reduced-intensity conditioning regimens with limited toxicity has allowed clinicians to offer ASCT to a growing number of older patients. The availability of Janus Kinase (JAK) 1/2 inhibitors allows clinicians to provide symptom relief and improved quality of life for MF patients. These drugs may also affect the decision regarding, in particular, the timing of ASCT. Future studies need to address the role of JAK1/2 inhibitors in patients who are transplantation candidates and determine their role before and, possibly, after transplantation. The identification of indications for the use of JAK1/2 inhibitors in the context of transplantation may lead to new therapeutic strategies for patients with MF.

An update on allogeneic hematopoietic progenitor cell transplantation for myeloproliferative neoplasms in the era of tyrosine kinase inhibitors

Myeloproliferative neoplasms are a category of diseases that have been traditionally amenable to allogeneic hematopoietic progenitor cell transplantation. Current developments in drug therapy have delayed transplantation for more advanced phases of the disease, especially for patients with CML, whereas transplantation remains a mainstream treatment modality for patients with advanced myelofibrosis and chronic myelomonocytic leukemia. Reduced-intensity conditioning has decreased the treatment-related mortality, and advances in the use of alternative donors for transplantation could extend the use of this procedure to an increasing number of patients with improved safety and efficacy. Here we review the current knowledge about allogeneic transplantation for myeloproliferative neoplasms and discuss the most important aspects to be considered when contemplating transplantation for patients with these diseases. Janus kinase 2 inhibitors offer the promise to improve spleen size and performance of patients with myelofibrosis and extend transplantation for patients with more advanced disease.

Allogeneic hematopoietic cell transplantation for myelofibrosis using fludarabine-, intravenous busulfan- and low-dose TBI-based conditioning

Graft failure is one of the major barriers to the success of allogeneic hematopoietic cell transplantation (HCT) in myelofibrosis (MF). We report our institutional experience with 27 MF patients who underwent HCT using fludarabine-, intravenous BU- and low-dose total body irradiation (FBT)-based reduced-intensity (n=20) or full-intensity (n=7) conditioning regimens. Eight patients had prior exposure to JAK1/2 inhibitor therapy; six patients received JAK1/2 inhibitors leading on to HCT and two patients received transplant at the failure of JAK1/2 inhibitor therapy. No adverse impact of JAK1/2 inhibitor therapy was observed on early post-transplant outcomes. All evaluable patients had neutrophil recovery, and no primary graft failure was observed. Cumulative incidence of grades II-IV acute GVHD at day 100 was 48% (95% confidence interval (CI), 29-67%) and chronic GVHD at 2 years was 66% (95% CI, 49-84%). Cumulative incidences of nonrelapse mortality (NRM), relapse and probability of OS at 2 years were: 43% (95% CI, 12-74%), 10% (95% CI, 0-39%) and 56% (95% CI, 28-77%), respectively. FBT-based conditioning regimen has a favorable impact on engraftment; however, further efforts are required to reduce NRM.

MPD-RC 101 prospective study of reduced-intensity allogeneic hematopoietic stem cell transplantation in patients with myelofibrosis

From 2007 to 2011, 66 patients with primary myelofibrosis or myelofibrosis (MF) preceded by essential thrombocythemia or polycythemia vera were enrolled into a prospective phase 2 clinical trial of reduced-intensity allogeneic hematopoietic stem cell transplantation (AHSCT), Myeloproliferative Disorder Research Consortium 101 trial. The study included patients with sibling donors (n = 32) receiving fludarabine/melphalan (FluMel) as a preparative regimen and patients with unrelated donors (n = 34) receiving conditioning with FluMel plus anti-thymocyte globulin (ATG). Patient characteristics in the 2 cohorts were similar. Engraftment occurred in 97% of siblings and 76% of unrelated transplants, whereas secondary graft failure occurred in 3% and 12%, respectively. With a median follow-up of 25 months for patients alive, the overall survival (OS) was 75% in the sibling group (median not reached) and 32% in the unrelated group (median OS: 6 months, 95% confidence interval [CI]: 3, 25) (hazard ratio 3.9, 95% CI: 1.8,8.9) (P < .001). Nonrelapse mortality was 22% in sibling and 59% in unrelated AHSCT. Survival correlated with type of donor, but not with the degree of histocompatibility match, age, or JAK2(V617F) status. In patients with MF with sibling donors, AHSCT is an effective therapy, whereas AHSCT from unrelated donors with FluMel/ATG conditioning led to a high rate of graft failure and limited survival. This trial was registered at www.clinicaltrials.gov as #NCT00572897.

Unrelated cord blood transplantation for patients with primary or secondary myelofibrosis

To determine whether umbilical cord blood transplantation (UCBT) is an alternative cure for myelofibrosis (MF), we evaluated 35 UCBTs reported to Eurocord. Seven patients had secondary acute myeloid leukemia (AML) at UCBT, and median age at UCBT was 54 years. Twenty-four patients received a reduced-intensity conditioning (RIC) regimen, and 17 of 35 patients received total body irradiation (2 to 12 Gy)-fludarabine-cyclophosphamide (TCF) conditioning. The median follow-up was 24 months. The cumulative incidence of neutrophil recovery at 60 days was 80%. Fifteen patients relapsed after UCBT. The 2-year overall survival and event-free-survival (EFS) rates were 44% and 30%, respectively. All patients given TCF achieved neutrophil and platelet recovery, and the use of TCF was associated with superior EFS in the RIC population (44% versus 0%, P = .001). Patients with transformation to AML had similar outcomes to patients with less advanced stages. In conclusion, despite graft failure remaining a major concern, the role of UCBT in the management of MF, especially using RIC TCF-based regimens, deserves further investigation to improve results.

Efficacy of ruxolitinib for myelofibrosis

INTRODUCTION

The discovery of the activating JAK2 V617F mutation in patients with myelofibrosis (MF) led to the development of JAK2 inhibitors. The first such inhibitor to enter clinical trials was ruxolitinib . This review summarizes preclinical and clinical data of ruxolitinib in MF.

AREAS COVERED

A literature search through Medline employing the terms 'ruxolitinib,' 'INCB018424' and 'myelofibrosis' was undertaken. The results from Phase I/II studies in patients with MF showed that ruxolitinib led to durable improvements in splenomegaly, and symptoms associated with MF. Two Phase III trials have compared ruxolitinib against placebo and best available therapy, and in both studies ruxolitinib demonstrated superior rates of spleen control and symptom improvement, and additional analysis demonstrated a survival benefit with ruxolitinib treatment. The main toxicities seen with ruxolitinib are cytopenias, which are managed with dose adjustments. Recent reports documented sporadic cases of immunosuppression-related infections. Ruxolitinib is the first drug ever approved for the therapy of patients with MF.

EXPERT OPINION

Understanding the factors that predict the rate and duration of response to ruxolitinib would improve our ability to manage patients treated with this medication. Clinical trials combining ruxolitinib with novel compounds that are also active in MF will further improve therapy for this disease.

The new landscape of therapy for myelofibrosis

The landscape of therapy for myelofibrosis (MF) is evolving at a pace not previously seen for this clonal myeloproliferative neoplasm. The discovery of the JAK2 V617F mutation in 2005 has led to the rapid development of therapy specifically developed for afflicted MF patients. Indeed, the successful phase III studies of ruxolitinib demonstrating improved symptomatic burden, splenomegaly and survival led to the first approved myelofibrosis drug in the United States and Europe. Multiple additional JAK2 inhibitors are currently in or nearing phase III testing, including SAR302503 (fedratinib), SB1518 (pacritinib) and CYT387 (momelotinib), seeking to offer incremental benefits to ruxolitinib in regards to cytopenias or other disease features. In parallel, phase III testing of pomalidomide is ongoing, with the goal of solidifying the role of immunomodulatory therapy in MF-associated anemia. Multiple single agents strategies are ongoing with histone deacetylase inhibitors, hedgehog inhibitors and hypomethylation agents. Incremental advances are further sought, either in additive or synergistic fashion, from combination strategies of ruxolitinib with multiple different approaches ranging from allogeneic stem cell transplant to current therapies mitigating anemia and further impacting the bone marrow microenvironment or histology. Transitioning from a pre-2011 era devoid of approved MF therapies to one of multiple agents that target not only disease course but symptomatic burden has indeed changed the platform from which MF providers are able to launch individualized treatment plans. In this article, we discuss the diagnostic and therapeutic milestones achieved through MF research and review the emerging pharmacologic agents on the treatment horizon.