Incidence and risk factors for early hepatotoxicity and its impact on survival in patients with myelofibrosis undergoing allogeneic hematopoietic cell transplantation

Indication and management of allogeneic haematopoietic stem-cell transplantation in myelofibrosis: updated recommendations by the EBMT/ELN International Working Group

New options for medical therapy and risk scoring systems containing molecular data are leading to increased complexity in the management of patients with myelofibrosis. To inform patients' optimal care, we updated the 2015 guidelines on indications for and management of allogeneic haematopoietic stem-cell transplantation (HSCT) with the support of the European Society for Blood and Marrow Transplantation (EBMT) and European LeukemiaNet (ELN). New recommendations were produced using a consensus-building methodology after a comprehensive review of articles released from January, 2015 to December, 2022. Seven domains and 18 key questions were selected through a series of questionnaires using a Delphi process. Key recommendations in this update include: patients with primary myelofibrosis and an intermediate-2 or high-risk Dynamic International Prognostic Scoring System score, or a high-risk Mutation-Enhanced International Prognostic Score Systems (MIPSS70 or MIPSS70-plus) score, or a low-risk or intermediate-risk Myelofibrosis Transplant Scoring System score should be considered candidates for allogeneic HSCT. All patients who are candidates for allogeneic HSCT with splenomegaly greater than 5 cm below the left costal margin or splenomegaly-related symptoms should receive a spleen-directed treatment, ideally with a JAK-inhibitor; HLA-matched sibling donors remain the preferred donor source to date. Reduced intensity conditioning and myeloablative conditioning are both valid options for patients with myelofibrosis. Regular post-transplantation driver mutation monitoring is recommended to detect and treat early relapse with donor lymphocyte infusion. In a disease where evidence-based guidance is scarce, these recommendations might help clinicians and patients in shared decision making.

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.

Splenomegaly in patients with primary or secondary myelofibrosis who are candidates for allogeneic hematopoietic cell transplantation: a Position Paper on behalf of the Chronic Malignancies Working Party of the EBMT

Splenomegaly is a hallmark of myelofibrosis, a debilitating haematological malignancy for which the only curative option is allogeneic haematopoietic cell transplantation (HCT). Considerable splenic enlargement might be associated with a higher risk of delayed engraftment and graft failure, increased non-relapse mortality, and worse overall survival after HCT as compared with patients without significantly enlarged splenomegaly. Currently, there are no standardised guidelines to assist transplantation physicians in deciding optimal management of splenomegaly before HCT. Therefore, the aim of this Position Paper is to offer a shared position statement on this issue. An international group of haematologists, transplantation physicians, gastroenterologists, surgeons, radiotherapists, and radiologists with experience in the treatment of myelofibrosis contributed to this Position Paper. The key issues addressed by this group included the assessment, prevalence, and clinical significance of splenomegaly, and the need for a therapeutic intervention before HCT for the control of splenomegaly. Specific scenarios, including splanchnic vein thrombosis and COVID-19, are also discussed. All patients with myelofibrosis must have their spleen size assessed before allogeneic HCT. Myelofibrosis patients with splenomegaly measuring 5 cm and larger, particularly when exceeding 15 cm below the left costal margin, or with splenomegaly-related symptoms, could benefit from treatment with the aim of reducing the spleen size before HCT. In the absence of, or loss of, response, patients with increasing spleen size should be evaluated for second-line options, depending on availability, patient fitness, and centre experience. Splanchnic vein thrombosis is not an absolute contraindication for HCT, but a multidisciplinary approach is warranted. Finally, prevention and treatment of COVID-19 should adhere to standard recommendations for immunocompromised 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.

Population Pharmacokinetics of Busulfan and Its Metabolite Sulfolane in Patients with Myelofibrosis Undergoing Hematopoietic Stem Cell Transplantation

For patients with myelofibrosis, allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only curative treatment to date. Busulfan-based conditioning regimens are commonly used, although high inter-individual variability (IIV) in busulfan drug exposure makes individual dose selection challenging. Since data regarding the IIV in patients with myelofibrosis are sparse, this study aimed to develop a population pharmacokinetic (PopPK) model of busulfan and its metabolite sulfolane in patients with myelofibrosis. The influence of patient-specific covariates on the pharmacokinetics of drug and metabolite was assessed using non-linear mixed effects modeling in NONMEM^®. We obtained 523 plasma concentrations of busulfan and its metabolite sulfolane from 37 patients with myelofibrosis. The final model showed a population clearance (CL) and volume of distribution (V_d) of 0.217 L/h/kg and 0.82 L/kg for busulfan and 0.021 L/h/kg and 0.65 L/kg for its metabolite. Total body weight (TBW) and a single-nucleotide polymorphism of glutathione-S-transferase A1 (GSTA1 SNP) displayed a significant impact on volume of distribution and metabolite clearance, respectively. This is the first PopPK-model developed to describe busulfan’s pharmacokinetics in patients with myelofibrosis. Incorporating its metabolite sulfolane into the model not only allowed the characterization of the covariate relationship between GSTA1 and the clearance of the metabolite but also improved the understanding of busulfan’s metabolic pathway.

The protective mechanism of resveratrol against hepatic injury induced by iron overload in mice

Excessive iron deposition can produce toxicity. Liver, as the main storage site of iron, is more vulnerable to excessive iron than other organs. Many studies have found that Resveratrol (RES) can effectively eliminate oxygen free radicals and resist lipid peroxide damage. However, studies investigating the mechanism of how RES prevents liver injury induced by iron overload are few. This study aims to observe the protective effect of RES on liver injury induced by iron overload in mice. Mice, except for the control group, received an intraperitoneal injection of iron dextran (50 mg/kg) every morning. The L-RES and H-RES groups received intragastric administration of low- and high-concentration RES solutions (20 or 50 mg/kg). The deferoxamine (DFO) group was intraperitoneally injected with DFO (50 mg/kg), while the control and iron overload groups were intraperitoneally injected with the same amount of normal saline every afternoon. Two weeks after continuous administration, iron-overloaded mice treated with high and low doses of RES significantly improved liver injury (GOT and GPT) and decreased LDH activity and MDA content and increased SOD and GSH activities (P < 0.01). Morphological tests showed that RES treatment can reduce liver iron deposition and improve liver pathological changes in iron-overloaded mice. Furthermore, RES treatment caused a significant decrease in Ft expression (P < 0.01). In conclusion, RES can alleviate liver injury in iron-overloaded mice. The mechanism may be related to improve the antioxidant capacity and reduce excess iron in the liver.

HLA-mismatched donor and high ferritin level showed poor clinical outcomes after allogeneic hematopoietic cell transplantation in patients with advanced myelofibrosis

Background:

Preconditioning intensity, donor choice and graft-versus-host disease (GVHD) prophylaxis of allogeneic hematopoietic cell transplantation (allo-HCT) for advanced myelofibrosis (MF) have not been fully elucidated.

Methods:

Thirty-five patients with advanced MF were treated with reduced-intensity conditioning (RIC) allo-HCT. We searched for matched sibling donors first, followed by matched or mismatched unrelated donors and familial mismatched donors. Preconditioning regimen consisted of fludarabine (total 150 mg/m²) and busulfan (total 6.4 mg/kg) with total body irradiation ⩽400cGy.

Results:

All showed engraftments, but four showed either leukemic relapse or delayed graft failure. Two-year overall survival (OS) and non-relapse mortality (NRM) was 60.0% and 29.9%, respectively. Acute GVHD was observed in 19 patients, and grade III–IV acute GVHD (eight grade III and four grade IV) was higher in human leukocyte antigen (HLA)-mismatched donor HCT compared with HLA-matched HCT (70% versus 20%). Chronic GVHD was observed in 16 patients, and a cumulative incidence of severe chronic GVHD was 33% in HLA-mismatched donor HCT and 7.7% in HLA-matched HCT. Significant hepatic GVHD was observed in nine patients (five acute, four chronic) and six of them died. Multivariate analysis revealed inferior OS in HLA-mismatched donor HCT (hazard ratio (HR) = 6.40, 95% confidence interval (CI) 1.6–25.7, p = 0.009) and in patients with high ferritin level at the time of pre-conditioning period (HR = 7.22, 95% CI 1.9–27.5, p = 0.004), which were related to higher incidence of hepatic GVHD with high NRM rate.

Conclusion:

RIC allo-HCT can be a valid choice providing graft-versus-fibrosis effect for advanced MF patients. However, HLA-mismatched donor and high pre-HCT ferritin level related to fatal hepatic GVHD should be regarded as poor-risk parameters.

Role of Inflammatory Factors during Disease Pathogenesis and Stem Cell Transplantation in Myeloproliferative Neoplasms

Hematopoiesis is a highly regulated and complex process involving hematopoietic stem cells (HSCs), cell surface adhesion molecules, and cytokines as well as cells of the hematopoietic niche in the bone marrow (BM). Myeloproliferative neoplasms (MPNs) are characterized by clonal expansion of HSCs involving one or more blood cell lineages. Philadelphia-negative MPNs (Ph-neg MPNs) comprise polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). In nearly all patients with Ph-neg MPN, mutations in the genes encoding janus kinase 2 (JAK2), calreticulin (CALR), or the thrombopoietin receptor (MPL) can be detected and, together with additional mutations in epigenetic modifier genes, these genetic aberrations contribute to the clonal expansion of the cells. In addition to these intracellular changes in the malignant clone, inflammatory processes involving both the clonal and the non-clonal cells contribute to the signs and symptoms of the patients, as well as to progression of the disease to myelofibrosis (MF) or acute leukemia, and to thrombotic complications. This contribution has been corroborated in preclinical studies including mouse models and patient-derived iPS cells, and in clinical trials, using anti-inflammatory drugs such as JAK inhibitors and steroids, or immunomodulatory drugs such as IMiDs and interferon-alpha (IFNa), all of which change the (im)balance of circulating inflammatory factors (e.g., TNFa, IL-1b, and TGFβ) in MPN. Currently, allogeneic hematopoietic (stem) cell transplantation (allo-HCT) remains the only curative treatment for Ph-neg MPN and is the treatment of choice in intermediate-2 and high-risk MF. HCT can reverse inflammatory changes induced by MPN as well as fibrosis in a large proportion of patients, but it also induces itself profound changes in inflammatory cells and cytokines in the patient, which may help to eradicate the disease but also in part cause significant morbidity (e.g., by graft-versus-host disease). In this review, we focus on the contribution of aberrant inflammation to disease pathogenesis in Ph-neg MPN as well as the current understanding of its alterations after allogeneic HCT.

Fludarabine/Busulfan Conditioning-Based Allogeneic Hematopoietic Cell Transplantation for Myelofibrosis: Role of Ruxolitinib in Improving Survival Outcomes

Allogeneic hematopoietic cell transplantation (allo-HCT) is the only curative treatment modality for primary myelofibrosis (MF) and related myeloproliferative neoplasms. Older age at diagnosis and age-related comorbidities make most patients ineligible for allo-HCT, given concerns for nonrelapse mortality (NRM). Here we report the outcomes of 37 consecutive recipients of allo-HCT for MF performed at a single center between 2009 and 2018 with a standardized institutional protocol. Most patients received ruxolitinib before HCT (n = 32), and those with splenomegaly >22 cm received pretransplantation splenic irradiation. The median age at HCT was 60 years (range, 40 to 74 years), and 68% of the cohort carried a JAK2 driver mutation. All patients received fludarabine/busulfan-based conditioning; 22 patients (59%) received a reduced-intensity conditioning regimen. All patients received peripheral blood grafts, from a matched sibling donor in 16 patients (43%), an unrelated donor in 20 patients, and a haploidentical-related donor in 1 patient. Sixty-one percent had a Hematopoietic Cell Transplantation Comorbidity Index ≥3, 40% had a Karnofsky Performance Status score <90, and 24% had a high-risk DIPSS Plus score. With a median follow-up of 40.2 months (range, 16.9 to 115 months), the 3-year overall survival and relapse-free survival were 81.1% (95% confidence interval [CI], 64.4% to 90.5%) and 78.4% (95% CI, 61.4% to 88.5%), respectively. Only 2 patients relapsed/progressed after transplant. NRM at 2 years was 16.2% (95% CI, 6.5% to 29.9%). All patients engrafted. Sixteen patients were treated with ruxolitinib post-transplantation for graft-versus-host disease, graft rejection/relapse, or persistent MF. These results suggest that pretransplantation ruxolitinib, fludarabine/busulfan-based conditioning, and splenic management are keys to improved transplantation outcomes in patients undergoing allo-HCT for MF.

Ruxolitinib Therapy Followed by Reduced-Intensity Conditioning for Hematopoietic Cell Transplantation for Myelofibrosis: Myeloproliferative Disorders Research Consortium 114 Study

We evaluated the feasibility of ruxolitinib therapy followed by a reduced-intensity conditioning (RIC) regimen for patients with myelofibrosis (MF) undergoing transplantation in a 2-stage Simon phase II trial. The aims were to decrease the incidence of graft failure (GF) and nonrelapse mortality (NRM) compared with data from the previous Myeloproliferative Disorders Research Consortium 101 Study. The plan was to enroll 11 patients each in related donor (RD) and unrelated donor (URD) arms, with trial termination if ≥3 failures (GF or death by day +100 post-transplant) occurred in the RD arm or ≥6 failures occurred in the URD. A total of 21 patients were enrolled, including 7 in the RD arm and 14 in the URD arm. The RD arm did not meet the predetermined criteria for proceeding to stage II. Although the URD arm met the criteria for stage II, the study was terminated owing to poor accrual and a significant number of failures. In all 19 transplant recipients, ruxolitinib was tapered successfully without significant side effects, and 9 patients (47%) had a significant decrease in symptom burden. The cumulative incidences of GF, NRM, acute graft-versus-host disease (GVHD), and chronic GVHD at 24 months were 16%, 28%, 64%, and 76%, respectively. On an intention-to-treat basis, the 2-year overall survival was 61% for the RD arm and 70% for the URD arm. Ruxolitinib can be integrated as pretransplantation treatment for patients with MF, and a tapering strategy before transplantation is safe, allowing patients to commence conditioning therapy with a reduced symptom burden. However, GF and NRM remain significant.

[Outcomes of reduced-intensity conditioning allogeneic hematopoietic stem cell transplantation for 10 patients with myelofibrosis]

Objective: To evaluate the efficacy of reduced-intensity conditioning allogeneic hematopoietic stem cell transplantation (RIC-allo-HSCT) for patients with myelofibrosis (MF). Methods: The clinical data of 10 patients with myelofibrosis (MF) who underwent RIC-allo-HSCT. Results: Of all 10 patients, 6 were male and 4 women, with a median age of 28.5 (22-54). Using fludarabine/busulfan plus total body irradiation (FB+TBI) pretreatment scheme based. Hematopoiesis reconstitution was achieved in 9 patients (90%). The median time of neutrophil and platelet engraftment was 13.5 (10-22) day and 16.5 (13-40) day, respectively. Acute GVHD occurred in 4 cases while chronic GVHD in 5 cases. The prospective OS for 3 years was (90.0±8.5)% after a median follow-up time of 17 months. Transplant related mortality was 1 case. Conclusion: RIC-HSCT with FB+TBI is a feasible and effective alternative for MF patients.

Myelofibrosis: to transplant or not to transplant?

Hematopoietic cell transplantation (HCT) is the only curative therapeutic modality for myelofibrosis (MF) at present. The optimal timing of HCT is not known in the presence of wider availability of less risky nontransplant therapies such as JAK 1/2 inhibitors. Careful review of patient, disease, and transplant-related factors is required in the appropriate selection of HCT vs the best available nontransplant therapies. We highlight some of the relevant issues and positioning of HCT in light of evolving data on JAK 1/2 inhibitors. The goal of this study is to provide the reader with updated evidence of HCT for MF, recognizing that knowledge in this area is limited by the absence of comparative studies between HCT and nontransplant therapies. Prospective studies are needed for better information on: the determination of optimal timing and conditioning regimens, the best way to integrate JAK inhibitors in the HCT protocols, and the impact of JAK inhibitors on graft-versus-host disease.

Allogeneic Hematopoietic Stem-Cell Transplantation for Myelofibrosis: A Practical Review

Myelofibrosis is a myeloproliferative neoplasm with cardinal features of extramedullary hematopoiesis, hepatosplenomegaly, cytopenias, and constitutional symptoms that result in shortened survival and leukemic transformation. It is a disease predominantly of the elderly, and currently available therapies only offer symptom control without curative benefit or ability to alter disease progression. Allogeneic hematopoietic stem-cell transplant (HSCT) is the only potentially curative intervention; however, this is only feasible in younger and medically fit patients and selectively offered to those with high-risk disease. Despite ongoing advancements, HSCT is associated with substantial morbidity and mortality, and the determination of which patients with myelofibrosis are ideal candidates and the selection of the opportune moment to proceed with transplantation remains challenging. This review summarizes our current recommendations for the role of and indications for HSCT in myelofibrosis.

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.

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.

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.

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.

Liver disease after hematopoietic cell transplantation in adults

Liver-related complications constitute a large component of the overall morbidity and mortality associated with hematopoietic cell transplantation. Affecting up to 80% of allogeneic HCT recipients, prompt recognition and treatment are essential. The differential diagnosis is broad and is best categorized by time of onset after transplantation. Early complications include drug-induced liver injury, sinusoidal obstruction syndrome, and graft-versus-host disease. Late complications include infectious sequelae, cirrhosis, and hepatic malignancies. Patients being considered for hematopoietic cell transplantation should be screened and evaluated for liver-related complications to help improve outcomes.

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.

Allogeneic transplantation for myelofibrosis: for whom, when, and what are the true benefits?

PURPOSE OF REVIEW

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only potentially curative therapy for myelofibrosis. Despite improved outcomes, morbidity and mortality of HSCT remain high. Here we examine recent data on patient selection, timing, and outcomes of HSCT in myelofibrosis.

RECENT FINDINGS

While there is a general effort to restrict HSCT to transplant-eligible intermediate-2 and high-risk patients, this group has comparatively worse HSCT outcomes, largely driven by their high transplant-related mortality (TRM). When adjusted for age, reduced intensity conditioning (RIC) has shown superior outcomes compared with myeloablative conditioning (MAC), making RIC-HSCT a viable option for older patients. Emerging concepts include the use of ruxolitinib pretransplant, optimizing MAC to decrease toxicity, and use of posttransplant JAK2-mutant allele burden to guide prophylactic immunotherapy to prevent relapse. The recognition of prognostic significance of somatic mutations in the ASXL1, EZH2, SRSF2, and IDH1/2 genes, and the improved assessment of risk of leukemic transformation have added a new dimension to risk stratification.

SUMMARY

Improving our understanding of molecular genetics and leukemic transformation holds promise for more precise patient selection for HSCT. Although RIC-HSCT may reduce TRM, further studies are needed to optimize conditioning regimens and to define the optimal timing of HSCT.

Cyclophosphamide followed by intravenous targeted busulfan for allogeneic hematopoietic cell transplantation: pharmacokinetics and clinical outcomes

Targeted busulfan ((T)BU) and cyclophosphamide (CY) for allogeneic hematopoietic cell transplantation carries a high risk of sinusoidal obstruction syndrome (SOS) in patients undergoing transplantation for myelofibrosis. We tested the hypothesis that reversing the sequence of administration (from (T)BU/CY to CY/(T)BU) would reduce SOS and day +100 nonrelapse mortality. We enrolled 51 patients with myelofibrosis (n = 20), acute myelogenous leukemia (n = 20), or myelodysplastic syndrome (n = 11) in a prospective trial of CY/(T)BU conditioning for allogeneic hematopoietic cell transplantation. CY 60 mg/kg/day i.v. for 2 days was followed by daily i.v. BU for 4 days, targeted to a concentration at steady state (Css) of 800-900 ng/mL. Compared with (T)BU/CY-conditioned patients, CY/(T)BU-conditioned patients had greater exposure to CY (P < .0001) and less exposure to 4-hydroxycyclophosphamide (P < .0001). Clinical outcomes were compared between cases and controls (n = 271) conditioned with (T)BU/CY for the same indications. In patients with myelofibrosis, CY/(T)BU conditioning was associated with a significantly reduced incidence of SOS (0% versus 30% after (T)BU/CY; P = .006), whereas the incidence of SOS was low in both cohorts with acute myelogenous leukemia/myelodysplastic syndrome. Day +100 mortality was significantly lower in the CY/(T)BU cohort (2% versus 13%; P = .01). CY/(T)BU conditioning had a marked affect on the pharmacokinetics of CY and was associated with significantly lower incidence of SOS and day +100 mortality, suggesting that CY/(T)BU is superior to (T)BU/CY as conditioning for patients with myelofibrosis.

Allogeneic hematopoietic cell transplantation for myelofibrosis in the era of JAK inhibitors

The discovery of JAK2617F mutation paved the way for the development of small molecule inhibitors of JAK1/2 resulting in first approved JAK1/2 inhibitor, ruxolitinib, for the treatment of patients with myelofibrosis (MF). Although JAK1/2 inhibitor therapy is effective in decreasing the burden of symptoms associated with splenomegaly and MF-related constitutional symptoms, it is neither curative nor effective in reducing the risk of leukemic transformation. Presently, allogeneic hematopoietic cell transplantation (HCT) is the only curative therapy for MF. A significant risk of regimen-related toxicities, graft failure, and GVHD are major barriers to the success of HCT in MF. Because of significant HCT-associated morbidity and mortality, divergent opinions regarding its appropriate role in this clinical situation have emerged. In this review, the risk-benefit ratios of modern drug therapy compared with HCT in MF patients are analyzed. A risk-adapted approach individualized to each patient's biologic characteristics and comorbidities is described, which is currently warranted in determining optimal treatment strategies for patients with MF. Inclusion of JAK1/2 inhibitor therapy in future transplant conditioning regimens may provide an opportunity to overcome some of these barriers, resulting in greater success with HCT for MF patients.