Stem cell transplantation for myelofibrosis: a report from two Canadian centers

Upfront allogeneic transplantation versus JAK inhibitor therapy for patients with myelofibrosis: a North American collaborative study

Allogeneic hematopoietic cell transplantation (HCT) is the only curative therapy for myelofibrosis (MF) and is recommended for patients with higher risk disease. However, there is a risk of early mortality, and optimal timing is unknown. JAK inhibitor (JAKi) therapy may offer durable improvement in symptoms, splenomegaly and quality of life. The aim of this multicentre, retrospective observational study was to compare outcomes of patients aged 70 years or below with MF in chronic phase who received upfront JAKi therapy vs. upfront HCT in dynamic international prognostic scoring system (DIPSS)-stratified categories. For the whole study cohort, median overall survival (OS) was longer for patients who received a JAKi vs. upfront HCT, 69 (95% CI 57-89) vs. 42 (95% CI 20-not reached, NR) months, respectively (p = 0.01). In patients with intermediate-2 and high-risk disease, median OS was 55 (95% CI 36-73) months with JAKi vs. 36 (95% CI 20-NR) months for HCT (p = 0.27). An upfront HCT strategy was associated with early mortality and difference in median OS was not observed in any risk group by 5 years of follow-up. Within the limitations of a retrospective observational study, we did not observe any benefit of a universal upfront HCT approach for higher-risk MF.

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

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

Survival following allogeneic transplant in patients with myelofibrosis

Allogeneic hematopoietic cell transplantation (HCT) is the only curative therapy for myelofibrosis (MF). In this large multicenter retrospective study, overall survival (OS) in MF patients treated with allogeneic HCT (551 patients) and without HCT (non-HCT) (1377 patients) was analyzed with Cox proportional hazards model. Survival analysis stratified by the Dynamic International Prognostic Scoring System (DIPSS) revealed that the first year of treatment arm assignment, due to upfront risk of transplant-related mortality (TRM), HCT was associated with inferior OS compared with non-HCT (non-HCT vs HCT: DIPSS intermediate 1 [Int-1]: hazard ratio [HR] = 0.26, P < .0001; DIPSS-Int-2 and higher: HR, 0.39, P < .0001). Similarly, in the DIPSS low-risk MF group, due to upfront TRM risk, OS was superior with non-HCT therapies compared with HCT in the first-year post treatment arm assignment (HR, 0.16, P = .006). However, after 1 year, OS was not significantly different (HR, 1.38, P = .451). Beyond 1 year of treatment arm assignment, an OS advantage with HCT therapy in Int-1 and higher DIPSS score patients was observed (non-HCT vs HCT: DIPSS-Int-1: HR, 2.64, P < .0001; DIPSS-Int-2 and higher: HR, 2.55, P < .0001). In conclusion, long-term OS advantage with HCT was observed for patients with Int-1 or higher risk MF, but at the cost of early TRM. The magnitude of OS benefit with HCT increased as DIPSS risk score increased and became apparent with longer follow-up.

Application of Stem Cell Therapy in Myelofibrosis

Myelofibrosis (MF) belongs to a group of clonal stem cell disorders known as the BCR-ABL-negative myeloproliferative neoplasms. Allogeneic hematopoietic stem cell transplantation (HCT) is currently the only curative treatment option for MF. Because HCT can be associated with significant morbidity and mortality, patients need to be carefully selected based on disease-risk, fitness, and transplant factors. Furthermore, in the era of JAK inhibitors, the timing of transplantation has become a challenging question. Here the authors review recent developments in HCT for MF, focusing on risk stratification and optimal timing.

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

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

Optimizing the Conditioning Regimen for Hematopoietic Cell Transplant in Myelofibrosis: Long-Term Results of a Prospective Phase II Clinical Trial

Optimal conditioning regimens for older patients with myelofibrosis undergoing allogeneic hematopoietic cell transplant are not known. Likewise, the role of dose intensity is not clear. We conducted a nonrandomized, prospective, phase II trial using low-dose, later escalated to high-dose (myeloablative conditioning), busulfan with fludarabine (Bu-Flu) in myelofibrosis patients up to age 74 years. The first 15 patients received i.v. busulfan 130 mg/m²/day on days -3 and -2 ("low dose"); 31 patients received high-dose conditioning, either 100 mg/m²/day (days -5 to -2; n = 4) or pharmacokinetic-guided area under the curve of 4000 μmol/min (days -5 to -2; n = 27). The primary endpoint was day 100 nonrelapse mortality (NRM). Median age was 58 years (interquartile range [IQR], 53-63). Dynamic international prognostic scoring system-plus was intermediate (n = 28) or high (n = 18). Donors were related (n = 19) or unrelated (n = 27). Cumulative incidence of NRM was 9.7% (95% confidence interval [CI], 0-20.3) at day 100 and at 3 years in the high-dose group and 0% in the low-dose group at day 100, which increased to 20% (95% CI, 0-41.9) at 3 years. With a median follow-up of 5.1 years (IQR, 3.8-6), 3-year relapse was 32.3% (95% CI, 15.4-49.1) in high dose versus 53.3% (95% CI, 26.6-80.1) in low dose. Event-free survival was 58% (95% CI, 43-78) versus 27% (95% CI, 12-62), and overall survival was 74% (95% CI, 60-91) versus 60% (95% CI, 40-91). In multivariate analysis, high-dose busulfan had a trend toward lower relapse (hazard ratio, .44; 95% CI, .18-1.07; P = .07), with no impact on NRM. Intensifying the Bu-Flu regimen using pharmacokinetic-monitoring appears to be promising in reducing relapse without increasing NRM.

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.

Reduced intensity allogeneic stem cell transplantation for younger patients with myelofibrosis

Allogeneic stem cell transplantation (alloSCT) is a curative procedure for myelofibrosis. Elderly people are mainly affected, limiting the feasibility of myeloablative regimens. The introduction of reduced-intensity conditioning (RIC) made alloSCT feasible for older patients. Nevertheless, the incidence of myelofibrosis is not negligible in young patients, who are theoretically able to tolerate high-intensity therapy. Very few data are available about the efficacy of RIC-alloSCT in younger myelofibrosis patients. This study included 56 transplanted patients aged <55 years. Only 30% had a human leucocyte antigen (HLA)-matched sibling donor, the others were transplanted from a fully-matched (36%) or partially-matched (34%) unrelated donor. All transplants were conditioned according the European Society for Blood and Marrow Transplantation protocol: busulfan-fludarabine + anti-thymocyte globulin, followed by ciclosporin and mycophenolate. One patient experienced primary graft failure. Incidence of graft-versus-host disease grade II-IV was 44% (grade III/IV 23%). One-year non-relapse mortality was 7% and the 5-year cumulative incidence of relapse was 19%. After a median follow-up of 8·6 years, the estimated 5-year progression-free survival and overall survival (OS) was 68% and 82%, respectively. Patients with fully-matched donor had a 5-year OS of 92%, in contrast to 68% for those with a mismatched donor (P = 0·03). The most important outcome-determining factor is donor HLA-matching. In conclusion, RIC-alloSCT ensures optimal engraftment and low relapse rate in younger myelofibrosis patients, enabling the possibility of cure in this group.

Understanding deregulated cellular and molecular dynamics in the haematopoietic stem cell niche to develop novel therapeutics for bone marrow fibrosis

Bone marrow fibrosis is the continuous replacement of blood-forming cells in the bone marrow with excessive scar tissue, leading to failure of the body to produce blood cells and ultimately to death. Myofibroblasts are fibrosis-driving cells and are well characterized in solid organ fibrosis, but their role and cellular origin in bone marrow fibrosis have remained obscure. Recent work has demonstrated that Gli1⁺ and leptin receptor⁺ mesenchymal stromal cells are progenitors of fibrosis-causing myofibroblasts in the bone marrow. Genetic ablation or pharmacological inhibition of Gli1⁺ mesenchymal stromal cells ameliorated fibrosis in mouse models of myelofibrosis. Conditional deletion of the platelet-derived growth factor (PDGF) receptor-α (PDGFRA) gene (Pdgfra) and inhibition of PDGFRA by imatinib in leptin receptor⁺ stromal cells suppressed their expansion and ameliorated bone marrow fibrosis. Understanding the cellular and molecular mechanisms in the haematopoietic stem cell niche that govern the mesenchymal stromal cell-to-myofibroblast transition and myofibroblast expansion will be critical to understand the pathogenesis of bone marrow fibrosis in both malignant and non-malignant conditions, and will guide the development of novel therapeutics. In this review, we summarize recent discoveries of mesenchymal stromal cells as part of the haematopoietic niche and as myofibroblast precursors, and discuss potential therapeutic strategies in the specific targeting of fibrotic transformation in bone marrow fibrosis. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Normal and leukemic stem cell niches: insights and therapeutic opportunities

Hematopoietic stem cells (HSCs) rely on instructive cues from the bone marrow (BM) niche to maintain their quiescence and adapt blood production to the organism's needs. Alterations in the BM niche are commonly observed in blood malignancies and directly contribute to the aberrant function of disease-initiating leukemic stem cells (LSCs). Here, we review recent insights into the cellular and molecular determinants of the normal HSC niche and describe how genetic changes in stromal cells and leukemia-induced BM niche remodeling contribute to blood malignancies. Moreover, we discuss how these findings can be applied to non-cell-autonomous therapies targeting the LSC niche.

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.

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.

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.

Hematopoietic stem cell transplantation for myelofibrosis: where are we now?

PURPOSE OF REVIEW

A succinct yet comprehensive review of the biology of myeloproliferative neoplasms and therapeutic options with a focus on rational decision making for hematopoietic stem cell transplantation.

RECENT FINDINGS

The introduction of Janus kinase inhibitors for myelofibrosis have ushered in a new era for treatment of constitutional symptoms and splenomegaly in myelofibrosis, but the effect of these agents on the natural history of the disease has yet to be clearly defined. Reduced intensity transplants have emerged as the preferred option with recent evidence suggesting fludarabine and melphalan as the optimal conditioning regimen.

SUMMARY

Myelofibrosis is a rare hematologic malignancy with limited curative therapeutic options. Significant advances in our understanding of disease pathogenesis have led to new targets and new therapeutic options are forthcoming. Hematopoietic stem cell transplantation is at present the only treatment with curative intent; however, the selection of patients who are likely to be best served by this procedure is difficult. As myelofibrosis is an extremely rare disease, randomized clinical trials specifically investigating the role of transplantation in myelofibrosis are unlikely to occur, thus current decision making processes are best guided by retrospective analyses from registry databases and single institution experiences.

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.

Allogeneic stem cell transplantation for myelofibrosis in 2012

Myelofibrosis (MF) is a heterogeneous disease for which long-term, effective medical therapeutic options are currently limited. The role of allogeneic haematopoietic stem cell transplant (AHSCT) in this population, many of whom are elderly, often provides a challenge with regard to the identification of suitable candidates, timing of transplantation in the disease course and choice of conditioning regimen. This review summarizes key findings from published data concerning AHSCT in MF and attempts to provide a state of the art approach to MF-AHSCT in 2012. In addition, we postulate on how the era of JAK inhibition might impact on transplantation for MF.

How to manage the transplant question in myelofibrosis

Allogeneic stem cell transplantation remains the only curative therapy for myelofibrosis. Despite advances in transplant, the morbidity and the mortality of the procedure necessitate careful patient selection. In this manuscript, we describe the new prognostic scoring system to help select appropriate patients for transplant and less aggressive therapies. We explore the advances in non-transplant therapy, such as with investigational agents. We review the blossoming literature on results of myeloablative, reduced intensity and alternative donor transplantation. Finally, we make recommendations for which patients are most likely to benefit from transplantation.

BCR-ABL1--negative myeloproliferative neoplasms: a review of molecular biology, diagnosis, and treatment

In 2008, the World Health Organization expanded the classification of myeloproliferative disorders based on increasing amounts of molecular and cytogenetic data. Myeloproliferative neoplasms (MPN) that do not contain the BCR-ABL1 mutation include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). JAK2V617F is the best characterized mutation in BCR-ABL1-negative neoplasms, with an estimated prevalence of more than 95% in PV, 50% in ET, and 50% in PMF. Current diagnostic strategies are increasingly reliant on molecular markers, and their prognostic value continues to be investigated. The use of aspirin, hydroxyurea, and phlebotomy for PV and ET, and the use of androgens, steroids, chemotherapy, and radiation therapy for PMF continues to be the mainstay of therapy. The only potentially curative therapy is allogeneic hematopoietic stem cell transplantation, but treatment-related mortality remains high. There have been promising results from clinical trials that involve the JAK tyrosine kinase inhibitors TG101384 and INCB018424, but their role in future therapy is yet to be established. Despite the optimism, it is increasingly apparent that pathogenicity in BCR-ABL1-negative MPN is more complex than for chronic myeloid leukemia, and a pathognomonic mutation may not be forthcoming.

Allogeneic hematopoietic cell transplantation for chronic myelofibrosis in Australia and New Zealand: older recipients receiving myeloablative conditioning at increased mortality risk

This retrospective registry analysis examined predictive factors for outcome in 57 patients who underwent allogeneic or syngeneic hematopoietic cell transplantation (HCT) for chronic myelofibrosis (CM), either primary (n = 49) or following an antecedent condition (n = 8), reported to the Australasian Bone Marrow Transplant Registry (ABMTRR) between 1993 and 2005. During the 6 years 2000 to 2005, 40 HCTs were performed for CM compared with 17 in the 7 years 1993 to 1999. Twenty-four recipients (42%) were age 50 or over at transplantation; all of these patients were transplanted after 1997, and 15 were given reduced intensity conditioning (RIC) pretransplantation. The cumulative incidence of transplantation-related mortality was 18% at 100 days and 25% at 1 year posttransplantation. Up to 1 year posttransplantation 16 patients died, with the most common causes being infection (n = 6) and graft-versus-host disease (GVHD) (n = 5). A total of 27 patients survived for 3 years or longer posttransplantation. None of these patients required regular red blood cell transfusions, and of the 17 who had not had splenectomies, none had detectable splenomegaly. Twelve patients had no detectable bone marrow fibrosis, 7 had grade 1 fibrosis, and in 8 patients no information was available. The overall survival (OS) probability for all patients was 72% at 1 year and 58% at 5 years posttransplantation. Patients age 50 and over who received myeloablative conditioning fared poorly, with 1-year overall actuarial survival of 44% compared with 77% for all other patients (P = .007). In multivariate analysis, age 50 years and over at transplantation was the only significant independent unfavorable risk factor for survival post-HCT (hazard ratio 2.71, 95% confidence interval 1.16-6.34, P = .02). This study shows a clear increase in annual numbers of allogeneic HCT performed for CM in Australia and New Zealand in recent years. Five-year survival was favorable compared with international studies, but for older recipients who received myeloablative conditioning, mortality risk was elevated.

Drug safety surveillance using de-identified EMR and claims data: issues and challenges

The author discusses the challenges of pharmacovigilance using electronic medical record and claims data. Use of ICD-9 encoded data has low sensitivity for detection of adverse drug events (ADEs), because it requires that an ADE escalate to major-complaint level before it can be identified, and because clinical symptomatology is relatively under-represented in ICD-9. A more appropriate vocabulary for ADE identification, SNOMED CT, awaits wider deployment. The narrative-text record of progress notes can potentially be used for more sensitive ADE detection. More effective surveillance will require the ability to grade ADEs by severity. Finally, access to online drug information that includes both a reliable hierarchy of drug families as well as structured information on existing ADEs can improve the focus and predictive ability of surveillance efforts.

The impact of bone marrow fibrosis on the outcome of hematopoietic stem cell transplantation

We retrospectively analyzed the data of 175 patients who underwent autologous (n = 69) or allogeneic hematopoietic stem cell transplantation (HCT) (n = 106) including 19 (27.5%) and 38 (35.8%) recipients who had bone marrow fibrosis (BMF) prior to transplantation, respectively. We investigated the effects of BMF on engraftment, graft-versus-host disease (GVHD), early posttransplant complications, and survival. Pretransplantation BMF did not delay engraftment and showed no impact either on early posttransplant complications or on the development of acute and/or chronic GVHD. Probability of 1-year overall survival (OS) and progression-free survival (PFS) of autologous HCT recipients were similar, namely 76.7% versus 88.6% (P > .005) and 26.33% versus 16.5% (P > .05) among patients with versus without fibrosis, respectively. In allogeneic HCT recipients, the probability of 1-year OS was 35.2% among patients with versus 48.9% among those without fibrosis (P = .004) PFS at 1 year was inferior among allogeneic HCT recipients with BMF: 27.8% versus 51.2% (P = .0008). Cox regression analysis revealed BMF to be independently associated with age, Sorror comorbidity index, primary disease, and disease status during HCT (P = .045).

Successful engraftment after reduced-intensity umbilical cord blood transplantation for myelofibrosis

Although allogeneic hematopoietic stem cell transplantation has recently been applied to patients with myelofibrosis with reproducible engraftment and resolution of marrow fibrosis, no data describe the outcomes of umbilical cord blood transplantation. We describe 14 patients with primary (n = 1) and secondary myelofibrosis (n = 13) who underwent reduced-intensity umbilical cord blood transplantation. Conditioning regimens included fludarabine and graft-versus-host disease prophylaxis composed cyclosporine/tacrolimus alone (n = 6) or a combination of tacrolimus and mycophenolate mofetil (n = 8). Thirteen patients achieved neutrophil engraftment at a median of 23 days. The cumulative incidence of neutrophil and platelet engraftment was 92.9% at day 60 and 42.9% at day 100, respectively. Posttransplantation chimerism analysis showed full donor type in all patients at a median of 14 days. The use of umbilical cord blood could be feasible even for patients with severe marrow fibrosis, from the viewpoint of donor cell engraftment.

Outcome of allogeneic stem cell transplantation following reduced-intensity conditioninig regimen in patients with idiopathic myelofibrosis: the g.I.T.m.o. Experience

Background:

Allogeneic stem cell transplantation (SCT) is a potentially curative treatment for myelofibrosis (MI), though limited by a high rate of transplant-related mortality (TRM). In the present study we evaluate the outcome of MI patients undergoing an allogenic SCT after reduced intensity conditioning (RIC) regimens, and the impact of prognostic factors.

Design and methods:

Fifty two patients were transplanted in 26 Italian centres between 1998 and 2006. We analyzed the influence of patient and disease clinical features before SCT and of transplant procedures on TRM and overall survival (OS) by means of univariate and multivariate analyses.

Results:

At SCT, median age was 52,5 years (32–68) and 89% of the patients had an intermediate or high Dupriez score. Conditioning regimens were based on fludarabine plus busulphan in 27% of patients, thiotepa plus cyclophosphamide in 46% and miscellaneous drug combinations in the other 27% of cases. Stem cells came from matched sibling donors for 75% of the patients and mismatched sibling or unrelated donors for the remaining 25%. The cumulative incidence of engraftment at day 90 after transplant was 83% (95% CI, 0.87–0.97). The estimated 1-year TRM was 30%. The estimated 3-year event-free-survival (EFS) and OS after hematopoietic SCT was 44% and 38% respectively. In multivariate analysis, an higher leukocyte count and circulating blasts in the peripheral blood before SCT significantly reduced EFS and OS respectively.

Interpretation and conclusions:

We conclude that the extension of the disease before transplantation based on the presence of circulating blasts and high leukocyte counts significantly affected the outcome after HSCT

Outcome of transplantation for myelofibrosis

Myelofibrosis is a myeloproliferative disorder incurable with conventional strategies. Several small series have reported long-term disease-free survival (DSF) after allogeneic hematopoietic cell transplantation (HCT). In this study, we analyze the outcomes of 289 patients receiving allogeneic transplantation for primary myelofibrosis between 1989 and 2002, from the database of the Center for International Bone Marrow Transplant Research (CIBMTR). The median age was 47 years (range: 18-73 years). Donors were HLA identical siblings in 162 patients, unrelated individuals in 101 patients, and HLA nonidentical family members in 26 patients. Patients were treated with a variety of conditioning regimens and graft-versus-host disease (GVHD) prophylaxis regimens. Splenectomy was performed in 65 patients prior to transplantation. The 100-day treatment-related mortality was 18% for HLA identical sibling transplants, 35% for unrelated transplants, and 19% for transplants from alternative related donors. Corresponding 5-year overall survival (OS) rates were 37%, 30%, and 40%, respectively. DFS rates were 33%, 27%, and 22%, respectively. DFS for patients receiving reduced-intensity transplants was comparable: 39% for HLA identical sibling donors and 17% for unrelated donors at 3 years. In this large retrospective series, allogeneic transplantation for myelofibrosis resulted in long-term relapse-free survival (RFS) in about one-third of patients.

Therapy of myelofibrosis (excluding JAK2 inhibitors)

Myelofibrosis shows a progressive clinical course and usually a poor, lethal prognosis. Allogeneic transplantation is an effective, potentially curable treatment approach although only a minority of patients may currently benefit from it. New effective treatment strategies are becoming available for this disease, including not only JAK2 inhibitors, but also other innovative drugs, targeting more general oncogenic mechanisms and the epigenetic control of cell proliferation and differentiation.

The role of allogeneic SCT in primary myelofibrosis: a British Society for Blood and Marrow Transplantation study

Fifty-one patients with primary myelofibrosis (PMF) received allogeneic haematopoietic stem cell transplants from related (n=33) or unrelated (n=18) donors. Twenty-seven patients, 19-54 years old, were prepared with myeloablative regimens including CY plus BU (n=4) or TBI (n=23). Twenty-four patients, 40-64 years old, received reduced-intensity conditioning (RIC) regimens. All RIC regimens contained fludarabine, combined with melphalan (n=19) or BU (n=5), and alemtuzumab or anti-thymocyte globulin (ATG) in the majority (n=19). Four patients (17%) in the RIC group had primary graft failure. Previous splenectomy reduced time to engraftment in the RIC group (13 versus 20 days; P=0.008). For MA and RIC groups, respectively, at 3 years, overall survival rates were 44 and 31% (P=0.67), progression-free survival 44 and 24% (P=0.87), and actuarial relapse rates 15 and 46% (P=0.06). Non-relapse mortality at 3 years was 41% for the myeloablative and 32% for the RIC group. Acute GVHD occurred in 29 and 38% of patients in the myeloablative and RIC groups, respectively. Extensive chronic GVHD developed in 30 and 35% of evaluable patients, respectively.

Allogeneic hemopoietic SCT for patients with primary myelofibrosis: a predictive transplant score based on transfusion requirement, spleen size and donor type

A total of 46 patients with primary myelofibrosis (PMF) (median age 51 years), underwent an allogeneic hemopoietic SCT (HSCT) after a thiotepa-based reduced-intensity conditioning regimen. The median follow-up for surviving patients is 3.8 years. In multivariate analysis, independent unfavorable factors for survival were RBC transfusions >20, a spleen size >22 cm and an alternative donor-24 patients had 0-1 unfavorable predictors (low risk) and 22 patients had 2 or more negative predictors (high risk). The overall actuarial 5-year survival of the 46 patients is 45%. The actuarial survival of low-risk and high-risk patients is, respectively, 77 and 8% (P<0.0001); this is because of a higher TRM for high-risk patients (RR, 6.0, P=0.006) and a higher relapse-related death (RR, 7.69; P=0.001). In multivariate Cox analysis, the score maintained its predictive value (P=0.0003), even after correcting for donor-patient age and gender, Dupriez score, IPSS (International Prognostic Scoring System) score pre-transplant and splenectomy. In conclusion, PMF patients undergoing an allogeneic HSCT may be scored according to the spleen size, transfusion history and donor type; this scoring system may be useful to discuss transplant strategies.

Survival in young patients with intermediate- / high-risk myelofibrosis: estimates derived from databases for non transplant patients

Recent studies have suggested that allogenic stem cell transplantation (allo-SCT) might be a better treatment option, compared to drug therapy, for young patients with high-/intermediate-risk primary myelofibrosis (PMF). However, there are no controlled studies that validate this contention and allo-SCT is associated with a substantial risk of procedure-related mortality and morbidity. In a retrospective analysis of nontransplant PMF patients, who were both young (age <60 years) and with high-/intermediate-risk disease, 1- and 3-year survival estimates were 87% and 55%, 95% and 77%, 71% and 58%, respectively, involving patients seen at three different centers with expertise in PMF; these data did not appear to be inferior to those published in the context of either myeloablative or reduced-intensity conditioning allo-SCT. These observations underscore the need for controlled studies to accurately assess the value of allo-SCT in PMF.

Allogeneic hematopoietic cell transplantation for patients with myelofibrosis

PURPOSE OF REVIEW

Hematopoietic cell transplantation (HCT) offers potentially curative therapy for patients with myelofibrosis. What is the current status?

RECENT FINDINGS

Changes in transplant strategies allow offering HCT to patients who, because of age or comorbid conditions, were not considered transplant candidates in the past. The omission of high-dose total body irradiation, adjusting doses of busulfan to achieve defined target levels, using fludarabine instead of cyclophosphamide as an immunosuppressive agent, the addition of melphalan, and the incorporation of antithymocyte globulin all appear to have contributed to better tolerability of new regimens. Reduced-intensity conditioning regimens are associated with a decrease in nonrelapse mortality and allow for successful HCT, even in patients 60-70 years of age. Some 50-75% of patients are cured by HCT. Emerging concepts include new prognostic scoring systems and novel molecular markers such as Janus kinase 2 mutations, which may aid in making treatment decisions and assessing remission status.

SUMMARY

Modifications of transplant-conditioning regimens have reduced transplant-related mortality and allow carrying out successful HCT in increasingly older patients. The selection of patients who should be transplanted, the optimal timing for transplantation, and pretransplant and posttransplant strategies remain challenging problems.

Reduced-intensity conditioning followed by allogeneic hematopoietic cell transplantation for adult patients with myelodysplastic syndrome and myeloproliferative disorders

Allogeneic hematopoietic cell transplantation (HCT) is the only curative strategy for patients with myelodysplastic syndrome (MDS) and myeloproliferative disorders (MPD). We report the results of 148 patients (median age = 59 years old) with de novo MDS (n = 40), acute myelogenous leukemia (AML) after antecedent MDS/MPD (n = 49), treatment-related MDS (t-MDS) (n = 25), MPD (n = 27), and chronic myelomonocytic leukemia (CMML) (n = 7) who underwent allogeneic HCT using a conditioning regimen of low-dose total body irradiation (TBI) alone (200 cGy) on day 0 (n = 5) or with the addition of fludarabine (Flu) 30 mg/m(2)/day on days -4 to -2 (n = 143). Postgrafting immunosuppression consisted of cyclosporine and mycophenolate mofetil (MMF). Seventy-five patients (51%) received an allograft from a matched related donor (MRD), and 73 patients (49%) were recipients of unrelated donor (URD) grafts. There was no significant difference in the incidence of acute (gr II-IV) and chronic extensive graft-versus-host disease (aGVHD, cGVHD) between the recipients of related and unrelated donor grafts. By day +28, 75% of patients demonstrated mixed T cell chimerism. Graft rejection was seen in 15% of patients. With a median follow-up of 47 (range: 6-89) months, the 3-year relapse-free survival (RFS) and overall survival (OS) are both 27% for all patients, with a relapse incidence of 41%. The 3-year RFS for the patients with de novo MDS, AML after antecedent MDS/MPD, t-MDS, MPD, and CMML were 22%, 20%, 29%, 37%, and 43%, respectively, and the 3-year OS was 20%, 23%, 27%, 43%, and 43%, respectively. The 3-year nonrelapse mortality (NRM) was 32%. Factors associated with a lower risk of relapse were the development of extensive cGVHD and having a low risk or intermediate-1 risk International Prognostic Score for the de novo MDS patients. Nonmyeloablative HCT confers remissions in patients who otherwise were not eligible for conventional HCT but for whom relapse is the leading cause of treatment failure.

Rapid regression of bone marrow fibrosis after dose-reduced allogeneic stem cell transplantation in patients with primary myelofibrosis

OBJECTIVE

To investigate the effect of a busulfan/fludarabine-based reduced intensity conditioning followed by allogeneic stem cell transplantation on regression of bone marrow fibrosis in patients with myelofibrosis.

METHODS

Twenty-four patients (male, n = 16; female, n = 8) with a median age of 52 years (range, 32-63 years) were included. Six patients were transplanted from human leukocyte antigen-identical siblings and 18 patients from matched unrelated donors. Diagnosis was primary myelofibrosis in 18 patients and secondary myelofibrosis in 6 patients; in 4 of them, primary myelofibrosis evolved from polycythemia vera, and in 2 of them from essential thrombocythemia. Using the European Consensus on grading bone marrow fibrosis, all patients had advanced marrow fibrosis MF-2 (n = 13) or MF-3 (n = 11) before allografting According to the Lille Risk Factor Scoring System, patients were classified as low risk (n = 5), intermediate risk (n = 16), or high risk (n = 3).

RESULTS

After stem cell transplantation, a complete (MF-0) or nearly complete (MF-1) regression of bone marrow fibrosis was seen in 59% at day +100, in 90% at day +180, and in 100% at day +360. No correlation between occurrence of acute graft-vs-host disease and fibrosis regression on day +180 was observed.

CONCLUSION

This study shows that allogeneic stem cell transplantation after reduced-intensity conditioning resulted in rapid regression of bone-marrow fibrosis.

A new MALDI-TOF-based assay for monitoring JAK2 V617F mutation level in patients undergoing allogeneic stem cell transplantation (allo SCT) for classic myeloproliferative disorders (MPD)

JAK2 V617F mutation is found in a high proportion of MPD patients. We developed a quantitative assay for the detection of the JAK2 mutation and demonstrated its clinical utility in MPD patients who underwent SCT. Sixty percent of the patients were JAK2 V617F positive prior to the SCT (mean mutation levels 74%, range 16-98%). After the procedure, the mutation levels progressively decreased and were in correlation with the donor-recipient chimerism status (r=0.97, p<0.001). At a median follow up of 16 months (range 2-58), 9/15 patients are alive and in CR. The levels of the JAK2 V617F mutation reached 0% in all surviving patients.

Philadelphia chromosome-negative myeloproliferative disorders: biology and treatment

The Philadelphia chromosome (Ph)-negative myeloproliferative disorders (MPDs) include essential thrombocythemia (ET), idiopathic myelofibrosis (IMF), and polycythemia vera (PV). All of these disorders are clonal hematologic malignancies originating at the level of the pluripotent hematopoietic stem cell. Recently, activating mutations of the intracellular cytokine-signaling molecule JAK2 have been identified in > 90% of patients with PV and in 50% of those with IMF and ET. In addition, a mutation of the thrombopoietin receptor, MPLW515L, has been documented in some patients with IMF. Both mutations activate JAK-STAT signaling pathways and likely play a role in disease progression. Both ET and PV are associated with prolonged clinical courses associated with frequent thrombotic and hemorrhagic events, and progression to myelofibrosis and acute leukemia. IMF has a much poorer prognosis and is associated with cytopenias, splenomegaly, extramedullary hematopoiesis, and bone marrow fibrosis. Stratification of risk for the development of complications from Ph-negative MPDs has guided the identification of appropriate therapies for this population. Intermediate/high-risk IMF or myelofibrosis after ET or PV is associated with a sufficiently poor prognosis to justify the use of allogeneic stem cell transplantation, which is capable of curing such patients. Reduced-intensity conditioning in preparation for allogeneic stem cell transplantation has permitted older patients with IMF to undergo transplantation with increasing success.

Allogeneic hematopoietic cell transplantation following reduced intensity conditioning for treatment of myelofibrosis

This report describes our experience with reduced intensity conditioning (RIC) allogeneic hematopoietic cell transplantation (HCT) using matched sibling and unrelated donors (MUDs) for treatment of myelofibrosis (MF). Nine patients with MF (median age, 54 years) were treated with RIC allogeneic HCT using MUDs for 7 of the 9 patients and sibling donors for 2 patients. By the Lille classification, 4 patients were characterized as having high risk, 4 as having intermediate risk, and 1 as having low risk. The RIC regimen consisted of fludarabine and a single dose of total body irradiation for the first patient and fludarabine/melphalan for the remaining 8 patients. Granulocyte colony-stimulating factor-primed peripheral blood stem cells (PBSCs) were used for all but 1 patient who received a total of 3 products because of graft failure, of which 2 were bone marrow cells and the third was PBSCs. Prophylaxis against graft-versus-host disease consisted of cyclosporin/mycophenolate with or without methotrexate. Seven patients were successfully engrafted with white blood cells, with an absolute neutrophil count > or =500 by a median of day +15 (range, 10-21 days). At the time of final fluorescence in situ hybridization and/or short tandem repeat analysis, 8 of 9 patients were chimeric, with 96%-100% donor cells and/or DNA. Five of the 9 patients were alive at the time of final contact, with a median follow-up of 32.2 months for the living patients. Overall survival probability at 1 year was 55.6% (95% confidence interval, 31.3%-77.4%). These results suggest that RIC MUD HCT using PBSCs can be an effective treatment for older patients with MF.

Biology and Treatment of Primary Myelofibrosis

Primary myelofibrosis (PMF) is a chronic myeloproliferative disorder associated with an average survival of less than 5 years. Therapy for PMF has used chemotherapeutic agents, immunomodulatory drugs, or biological-response modifiers that have not always been directed at the biological processes that underlie the origins of PMF. Such strategies are palliative and have an uncertain effect on survival. At present, allogeneic stem cell transplantation (ASCT) is the only means of altering the natural history of patients with PMF and provides the only hope for cure of this disorder. Enthusiasm for ASCT in PMF has been muted due to an unacceptable transplantation-related morbidity and mortality in patients receiving fully myeloablative conditioning regimens. Recently, a variety of reduced-intensity conditioning regimens have been utilized in older patients with PMF with significant comorbidities with promising results. Greater understanding of the cellular and molecular events that lead to the development of PMF have provided the opportunity for targeted therapies for PMF. Such therapies must be first evaluated in phase 1/2 trials using a variety of endpoints to assess their efficacy and their potential associated toxicities. The performance of randomized clinical trials comparing these agents to the present standard of care would permit for the first time evidence-based therapeutic decisions to be made for patients with PMF.

Advances in the therapy of chronic idiopathic myelofibrosis

The molecular basis of chronic idiopathic myelofibrosis (CIMF) has remained elusive, thus hampering the development of effective targeted therapies. However, significant progress regarding the molecular mechanisms involved in the pathogenes is of this disease has been made in recent years that will likely provide ample opportunity for the investigation of novel therapeutic approaches. At the fore front of these advances is the discovery that 35%-55% of patients with CIMF harbor mutations in the Janus kinase 2 tyrosine kinase gene. Until very recently, the management of patients with CIMF involved the use of supportive measures, including growth factors, transfusions, or interferon, and the administration of cyto-reductive agents, such as hydroxyurea and anagrelide. However, several trials have demonstrated the efficacy of antiangiogenic agents alone or in combination with corticosteroids. In addition, the use of reduced-intensity conditioning allogeneic stem cell transplantation has resulted in prolonged survival and lower transplant-related mortality.

Allogeneic stem cell transplantation as treatment for myelofibrosis

Idiopathic myelofibrosis (IMF) is a clonal disorder resulting from the proliferation of aberrant hematopoietic stem cells. Conventional treatment is unsatisfactory, and with the exception of supportive blood transfusions, none of the standard therapies have been shown to confer a survival advantage. Allogeneic stem cell transplantation represents the only treatment modality with proven curative potential. Myeloablative conditioning regimens are associated with high transplant-related mortality, particularly in the elderly, making most patients with IMF ineligible for this treatment. Strategies using reduced intensity conditioning regimes have allowed application of allogeneic transplantation to a broader range of patients and a number of recent reports have demonstrated potential efficacy.

Different outcome of allogeneic transplantation in myelofibrosis using conventional or reduced-intensity conditioning regimens

Allogeneic haematopoietic stem cell transplantation remains the only curative treatment of myelofibrosis with myeloid metaplasia (MMM). Previous reports have indicated significant treatment-related mortality (TRM) for patients transplanted after myeloablative conditioning but superior survival has been reported after reduced-intensity conditioning (RIC). We report the results of a survey of all allogeneic transplantations for MMM performed in Sweden at six transplant units between 1982 and 2004. Twenty-seven patients were transplanted; 17 with a myeloablative conditioning regimen and 10 with RIC. The median age was 50 years (5-63 years) at transplantation. After a median follow up of 55 months, 20 patients are alive. TRM was 10% in the RIC group and 30% in the myeloablative group. There was no difference in survival for high or low-risk patients according to Cervantes score or between sibling and unrelated donor transplantations.

Morphology of the bone marrow after stem cell transplantation

In many haematological conditions the only curative option is stem cell (SCT) or bone marrow (BM) transplantation. Little information exists about BM morphology following non-ablative engraftment. During the pretransplantation period and depending on the kind of pretreatment, there may be hypoplasia, residual disease and varying degrees of fibrosis. In the post-transplantation period, after 1-3 weeks of transfusion-dependent pancytopenia, the first signs of successful engraftment are indicated by the recurrence of neutrophils, monocytes and erythrocytes in the peripheral blood. In the BM there is slow regeneration of erythropoiesis, followed by the other lineages of haematopoiesis and increase in reticulin fibres or even a resolution of fibrosis. Diagnostic problems arise when neoplastic lympho- or haematopoiesis are maintained following transplantation. Moreover, there may be a significant graft versus tumour response reaction or an already relapsing disease needing aggressive treatment. On the other hand, a conspicuous dyshaematopoiesis should not be mistaken as representing a myelodysplastic syndrome. The presence of granulomas being treatment-related or a manifestation of intercurrent granulomatous disease has to be considered. More advanced knowledge of the histological features of regenerating BM will certainly aid the recognition of relapsing disease and is needed for the adequate reporting of post-transplant alterations associated with a successful or failing engraftment.

Allogeneic hematopoietic stem cell transplantation for myelofibrosis

PURPOSE OF REVIEW

This review summarizes the current status and new developments in allogeneic hemopoietic stem cell transplantation strategies for patients with myelofibrosis with myeloid metaplasia, focusing on novel concepts of allogeneic transplantation with reduced-intensity conditioning.

RECENT FINDINGS

No substantial progress has been made in the conventional management of myelofibrosis with myeloid metaplasia. Allogeneic hemopoietic stem cell transplantation represents the only treatment modality with proven curative potential. Standard-dose conditioning regimes followed by allogeneic transplantation are associated with a relatively high transplant-related mortality. Reduced-intensity conditioning regimens have substantially reduced treatment-related mortality. This result is from three studies on myelofibrosis with myeloid metaplasia including more than 60 patients overall. The optimal conditioning regimen for this condition is unknown, in particular the utility of using T-cell depleted stem cells to reduce graft versus host disease is not documented. Emerging concepts include new risk classification for a better provision of the transplant outcome, and splenectomy before transplantation for reducing tumor burden.

SUMMARY

The data on hemopoietic stem cell transplantation with reduced-intensity conditioning in myelofibrosis with myeloid metaplasia are encouraging. An accurate risk stratification is a pivotal procedure for selecting patients who will receive the greatest benefit for transplantation. Reduced-intensity conditioning should be further evaluated within clinical trials, in particular for assessing the role of splenectomy and for testing the optimal conditioning regimen.