Complete remission of idiopathic myelofibrosis following donor lymphocyte infusion after failure of allogeneic transplantation: demonstration of a graft-versus-myelofibrosis effect

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

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

Incidence and Outcome of Late Relapse after Allogeneic Stem Cell Transplantation for Myelofibrosis

In this cross-sectional study, we retrospectively evaluated the files of 227 patients with myelofibrosis who underwent transplantation between 1994 and 2015 for relapse later than 5 years after allogeneic stem cell transplantation (SCT). A total of 94 patients who were alive and in remission at 5 years were identified with follow-up of at least 5 years (median, 9.15 years) after SCT. Thirteen patients (14%) experienced late molecular (n = 6) or hematologic (n = 7) relapse at a median of 7.1 years while 81 patients did not experience relapse. Relapse patients received either donor lymphocyte infusion (DLI) (n = 7) and/or second transplantation (n = 4). Of those, 72.7% achieved again full donor cell chimerism and molecular remission, and after a median follow-up of 45 months, the 3-year overall survival rates for patients with or without relapse were 90.9% (95% confidence interval [CI], 77% to 100%) and 98.8% (95% CI, 96% to 100%), respectively (P = .13). We conclude that late relapse occurs in about 14% of the patients and the majority can be successfully salvaged with DLI and/or second allograft. All patients with molecular relapse are alive and support the long-time molecular monitoring in myelofibrosis patients after allogeneic SCT.

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.

Immunotherapy in Myeloproliferative Diseases

Myeloproliferative diseases, including myeloproliferative neoplasms (MPN) and myelodysplastic syndromes (MDS), are driven by genetic abnormalities and increased inflammatory signaling and are at high risk to transform into acute myeloid leukemia (AML). Myeloid-derived suppressor cells were reported to enhance leukemia immune escape by suppressing an effective anti-tumor immune response. MPNs are a potentially immunogenic disease as shown by their response to interferon-α treatment and allogeneic hematopoietic stem-cell transplantation (allo-HSCT). Novel immunotherapeutic approaches such as immune checkpoint inhibition, tumor vaccination, or cellular therapies using target-specific lymphocytes have so far not shown strong therapeutic efficacy. Potential reasons could be the pro-inflammatory and immunosuppressive microenvironment in the bone marrow of patients with MPN, driving tumor immune escape. In this review, we discuss the biology of MPNs with respect to the pro-inflammatory milieu in the bone marrow (BM) and potential immunotherapeutic approaches.

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.

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

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

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.

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

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

Indications and outcomes of reduced-toxicity hematopoietic stem cell transplantation in adult patients with hematological malignancies

Hematopoietic stem cell transplantation (HCT) utilizing non-myeloablative (NMA) and reduced-intensity conditioning (RIC) regimens (collectively referred to as reduced-toxicity HCT, RT-HCT) has become a viable therapeutic option for patients with hematological malignancies who are ineligible for standard myeloablative conditioning transplantation (MA-HCT). RT-HCT has been shown to induce stable engraftment with low toxicity, and to produce similar overall and progression-free survival (PFS) when compared to MA-HCT in acute myeloid leukemia and myelodysplastic syndrome. The best results for RT-HCT have been reported for patients with disease that is in remission, indolent and chemosensitive, and with a strong graft-versus-malignancy effect. Chronic graft-versus-host disease seems to correlate with a lower relapse rate and better PFS. RT-HCT is inferior when performed in poor risk or advanced disease, due to high relapse rates. A search for novel strategies that includes the most appropriate conditioning regimens and post-transplant immunomodulation protocols with more intensive anti-malignancy activity but limited toxicity is in progress. This review provides an update on the results of clinical studies of RT-HCT, and discusses possible indications and investigative strategies for improving the clinical outcomes of RT-HCT for the major hematological malignancies.

Myelofibrosis: an update on current pharmacotherapy and future directions

INTRODUCTION

Myelofibrosis (MF) is a myeloproliferative neoplasm characterized by symptoms mainly derived from anemia and splenomegaly and constitutional symptoms and associated with a median survival around 6 years. Allogeneic stem cell transplantation (allo-SCT) remains the only curative therapy of MF but is applicable to a minority of patients. Discovery of the JAK2 mutation has provided the basis for the introduction of a new class of drugs, the JAK inhibitors, in the treatment of MF.

AREAS COVERED

A literature review on the therapy of MF has been performed through a PubMed search, with special attention being paid to the available data on transplantation, the JAK inhibitors, and other new drugs.

EXPERT OPINION

Conventional therapy of MF is usually adjusted to the predominant clinical symptoms in each patient, and its impact on survival is limited. Reduced-intensity conditioning regimens have increased the number of patients eligible for allo-SCT, but this procedure is still associated with substantial morbidity and mortality. The JAK inhibitors, such as ruxolitinib, can achieve profound symptomatic relief of the splenomegaly and the constitutional symptoms. However, they often accentuate the anemia and do not reduce the JAK2 allele burden, therefore lacking the potential to modify the natural history of MF.

Donor lymphocyte infusions and second transplantation as salvage treatment for relapsed myelofibrosis after reduced-intensity allografting

Thirty myelofibrosis patients (21 males, nine females) with relapse (n = 27) or graft-rejection (n = 3) after dose-reduced allografting underwent a salvage strategy including donor lymphocyte infusions (DLIs) and/or second allogeneic haematopoietic stem cell transplantation (HSCT). Twenty-six patients received a median number of three (range, 1-5) DLIs in a dose-escalated mode starting with a median dose of 1·2 × 10(6) (range, 0·003-8 × 10(6) ) up to median dose of 40 × 10(6) T-cells/kg (range, 10-130 × 10(6) ). 10/26 patients (39%) achieved complete response (CR) to DLIs. Acute (grade II-IV) and chronic graft-versus-host (GvHD) disease occurred in 12% and 36% cases. Thirteen non-responders to DLI and four patients who did not receive DLI due to graft-rejection or acute transformation of the blast phase underwent a second allogeneic HSCT from alternative (n = 15) or the same (n = 2) donor. One patient (6%) experienced primary graft-failure and died. Acute (II-IV) and chronic GvHD were observed in 47% and 46% of patients. Overall responses after second HSCT were seen in 12/15 patients (80%: CR: n = 9, partial response: n = 3). The 1-year cumulative incidence of non-relapse mortality for recipients of a second allograft was 6%, and the cumulative incidence of relapse was 24%. After a median follow-up of 27 months, the 2-year overall survival and progression-free survival for all 30 patients was 70% and 67%, respectively. In conclusion, our two-step strategy, including DLI and second HSCT for non-responding or ineligible patients, is an effective and well-tolerated salvage approach for patients relapsing after reduced-intensity allograft after 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.

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.

Reduced-intensity conditioning followed by allogeneic hematopoietic stem cell transplantation in myelofibrosis

Hematopoietic stem cell transplantation offers a curative therapy for patients with myelofibrosis. Because of toxicity, allografting following myeloablative regimens is mainly applicable to young patients. With the introduction of dose-reduced conditioning using busulfan or melphalan with fludarabine, transplantation has become tolerable also for older patients. Implementation of antithymocyte globulin in the conditioning has resulted in effective prevention of graft-versus-host disease and an increased use of alternative donors. Through the discovery of new disease-specific mutations, close monitoring of residual disease became feasible in many patients and the outcome of posttransplant strategies improved. Still challenging is the achievement of new, transplant-derived models to estimate risk status and possible outcome for every individual patient, to help in therapeutic decision making and the determination of the optimal timing of stem cell transplantation. Such a tool may optimally include not only clinicomorphologic characteristics but also other potentially relevant factors such as cytogenetics and novel molecular markers.

Screening and monitoring of MPL W515L mutation with real-time PCR in patients with myelofibrosis undergoing allogeneic-SCT

Monitoring of minimal residual disease (MRD) after allogeneic (allo)-SCT for myelofibrosis (MF) allows recognizing the depth of remission and thus guides application of appropriate therapeutic interventions. MPL W515L/K mutations, which are detected in 5-10% of JAK2V617F-negative patients, may be useful for this purpose. Using a highly sensitive quantitative PCR method, we tested 90 patients with MF who underwent allo-SCT for the presence of MPL W515L/K mutations. Two patients with primary MF were found to harbor MPLW515L while no patient was positive for MPLW515K mutation. Both patients were JAK2V617F negative and cleared the mutation rapidly after allo-SCT and remained negative for a median follow-up of 19 months. The results of molecular monitoring correlated well with other remission parameters such as normalization of peripheral blood counts and morphology and complete donor chimerism. We conclude that MPLW515L can be cleared after allo-SCT and hence may be used as an MRD marker in a proportion of JAK2V617F-negative MF patients.

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

From 2002 to 2007, 103 patients with primary myelofibrosis or postessential thrombocythemia and polycythemia vera myelofibrosis and a median age of 55 years (range, 32-68 years) were included in a prospective multicenter phase 2 trial to determine efficacy of a busulfan (10 mg/kg)/fludarabine (180 mg/m(2))-based reduced-intensity conditioning regimen followed by allogeneic stem cell transplantation from related (n = 33) or unrelated donors (n = 70). All but 2 patients (2%) showed leukocyte and platelet engraftment after a median of 18 and 22 days, respectively. Acute graft-versus-host disease grade 2 to 4 occurred in 27% and chronic graft-versus-host disease in 43% of the patients. Cumulative incidence of nonrelapse mortality at 1 year was 16% (95% confidence interval, 9%-23%) and significantly lower for patients with a completely matched donor (12% vs 38%; P = .003). The cumulative incidence of relapse at 3 years was 22% (95% confidence interval, 13%-31%) and was influenced by Lille risk profile (low, 14%; intermediate, 22%; and high, 34%; P = .02). The estimated 5-year event-free and overall survival was 51% and 67%, respectively. In a multivariate analysis, age older than 55 years (hazard ratio = 2.70; P = .02) and human leukocyte antigen-mismatched donor (hazard ratio = 3.04; P = .006) remained significant factors for survival. The study was registered at www.clinicaltrials.gov as #NCT 00599547.

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.

Donor lymphocyte infusions: the long and winding road: how should it be traveled?

Donor lymphocyte infusions (DLI) often are used after allo-SCT to augment the graft-versus-tumor effect. Timing of infusion varies according to indication, for example to treat tumor recurrence, as a planned strategy to prevent disease relapse in the setting of T-cell-depleted grafts or non-myeloablative conditioning regimens, or as a method to convert mixed to full donor chimerism. The optimal strategy of timing, use of cytotoxic conditioning, cell dose and cell product composition, and so on, for DLI administration remains unclear. Despite varied techniques, DLI may lead to 3-year disease-free survivals (DFS) in excess of 60% for all CML patients and approach 90% in patients with only molecular or cytogenetic relapse. Other hematologic malignancies appear much less responsive, as less than 50% of patients respond and provide, at best, 3-year DFS rates of 20-50%. Multiple myeloma patients have overall response rates of 40-45% after DLI, suggesting benefit in relapsed disease, but limited experiences for diseases such as Hodgkin's lymphoma, myelodysplasia and ALL preclude recommendations for use of DLI at this time. Regardless of the indication, treatment-related mortality after DLI is 5-20% and more than one-third of patients will develop acute and/or chronic GVHD after DLI. The risks of these complications appear related, in part, to donor source, cell dose and therapy prior to DLI. Although there are no definitive answers, the information gleaned from published literature suggests that DLI should be administered early after relapse or as a prophylactic strategy in patients receiving T-cell-depleted grafts, and patients with bulky or aggressive disease may benefit from disease reduction prior to DLI.

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.

Idiopathic myelofibrosis: pathogenesis to treatment

Idiopathic myelofibrosis (IMF) is the least common of the chronic myeloproliferative disorders and carries the worst prognosis with a median survival of 4 years. It is a clonal haematopoietic stem-cell disorder and, although the pathogenesis remains unclear, approximately 50% of cases are known to possess an activating JAK2 V617F mutation. In contrast, the characteristic stromal proliferation is a reactive, or secondary, event that results from the aberrant release of a variety of growth factors from megakaryocytes and monocytes. Treatment for most cases is supportive, although androgens, recombinant erythropoietin, steroids and thalidomide are effective modalities for the amelioration of anaemia. Myelosuppression, splenectomy and irradiation are valuable therapeutic modalities for specific clinical situations. Prognostic scores are available to aid the identification of cases for whom bone marrow transplantation should be considered. Recently, the use of reduced intensity conditioning has resulted in prolonged survival and lower transplant-related mortality. This review summarises the recent advances in the disease's pathogenesis and discusses the role of the various therapeutic options.

The graft-versus-lymphoma effect: clinical review and future opportunities

Numerous lines of preclinical and clinical evidence support the existence of a graft-versus-leukemia effect, but less evidence supporting a comparable graft-versus-lymphoma effect exists. We review here current clinical data addressing the graft-versus-lymphoma effect, including comparisons of autologous, syngeneic, and allogeneic transplantation; responses to immunomodulation; and responses to nonmyeloablative stem cell transplantation. Despite several limitations of the data, we believe that there is sufficient evidence suggesting a significant graft-versus-lymphoma effect. In addition, we discuss approaches for clinical management of lymphoma patients, opportunities for mechanistic studies afforded by donor leukocyte infusions and nonmyeloablative transplantation, and suggestions for clinical studies to further define the magnitude and applicability of the graft-versus-lymphoma effect.

Allogeneic hematopoietic stem-cell transplantation with reduced-intensity conditioning in intermediate- or high-risk patients with myelofibrosis with myeloid metaplasia

A total of 21 patients with myelofibrosis with myeloid metaplasia (MMM), with a median age of 54 years (range, 27-68 years), were prepared with a reduced-intensity conditioning (RIC) regimen. The patients received an allogeneic marrow (n = 3) or peripheral blood stem-cell (n = 18) transplant from HLA-matched related (n = 18) or unrelated (n = 2), or 1 Ag-mismatched related (n = 1), donors. RIC regimens included fludarabine/total body irradiation 200 cGy (n = 5) or 450 cGy (n = 1), fludarabine/melphalan (n = 7), thiotepa/cyclophosphamide (n = 7), and thiotepa/fludarabine (n = 1). At the time of transplantation, all of the patients were at intermediate (n = 13) or high (n = 8) risk, according to the Dupriez classification. Of the patients, 19 had grade III or IV marrow fibrosis. All of the patients achieved full engraftment but one. Posttransplantation chimerism analysis showed more than 95% donor cells in 18 patients, while 2 patients achieved complete donor chimerism after donor leukocyte infusion (DLI). Acute graft-versus-host disease (GVHD) grades II to IV was observed in 7 patients, grades III to IV in 2, and extensive chronic GVHD in 8 of 18 evaluable patients. There were 3 patients who died from acute GVHD, infection, and relapse. There are 18 patients alive 12 to 122 months (median, 31 months) after transplantation, and 17 are in remission (1 after a second transplantation). The use of RIC regimens in allogeneic stem cell transplantation results in prolonged survival in intermediate/high-risk MMM patients.

Pilot study of reduced-intensity conditioning followed by allogeneic stem cell transplantation from related and unrelated donors in patients with myelofibrosis

A prospective pilot study was performed to evaluate the effect of reduced-intensity conditioning with busulphan (10 mg/kg), fludarabine (180 mg/qm) and anti-thymocyte globulin followed by allogeneic stem cell transplantation from related (n = 8) and unrelated donors (n = 13) in 21 patients with myelofibrosis. The median age of the patients was 53 years (range, 32-63). No primary graft failure occurred. The median time until leucocyte (>1.0 x 10(9)/l) and platelet (>20 x 10(9)/l) engraftment was 16 (range, 11-26) and 23 d (range, 9-139) respectively. Complete donor chimaerism on day 100 was seen in 20 patients (95%). Acute graft-versus-host disease (GvHD) grades II-IV and III/IV occurred in 48% and 19% of cases and 55% of the patients had chronic GvHD. Treatment-related mortality was 0% at day 100 and 16% [95% confidence interval (CI): 0-32%] at 1 year. Haematological response was seen in 100% and complete histopathological remission was observed in 75% of the patients and 25% of the patients showed partial histopathological remission with a continuing decline in the grade of fibrosis. After a median follow-up of 22 months (range, 4-59), the 3-year estimated overall and disease-free survival was 84% (95% CI: 67-100%).

Modern management of myelofibrosis

The conventional treatment of myelofibrosis involves a wait-and-see approach for asymptomatic patients, oral chemotherapy for the hyperproliferative forms of the disease, androgens or erythropoietin for the anaemia, and splenectomy in selected patients. Low-dose thalidomide plus prednisone is a well-tolerated therapy for the anaemia and the thrombocytopenia of myelofibrosis, whereas imatinib has shown little efficacy. Allogeneic stem cell transplantation (allo-SCT) is the only curative therapy for myelofibrosis. Its standard modality has an associated mortality of about 30% and can be applied to younger patients with high-risk disease or resistant to conventional treatment. Reduced-intensity conditioning allo-SCT involves a low mortality and is a promising therapy for patients aged 45-70 years old with the above characteristics. Autologous SCT is a palliative therapy for patients resistant to conventional treatment who lack a suitable donor. The next candidates for the treatment of myelofibrosis are the thalidomide derivatives, the proteasome inhibitors, and vascular endothelial growth factor neutralizing antibodies.

Outcome of allogeneic stem cell transplantation in patients with myelofibrosis

Myelofibrosis, either de novo or following pre-existing hematologic diseases, can be cured by allogeneic hematopoietic stem cell transplantation (SCT), but SCT is associated with significant morbidity and mortality, making the choice and timing of transplantation difficult. In all, 20 patients (seven female and 13 male), with a median age of 45 years (range 22-57 years), with idiopathic myelofibrosis (n = 12), post-thrombocythemic (n = 3) or post-polycythemic (n = 2) myeloid metaplasia or leukemic transformation (n = 3), underwent allogeneic SCT at our center between 1994 and 2003. With regard to the pre-transplant presence of risk factors such as hemoglobin levels < or =10 mg/dl, grade III marrow fibrosis or peripheral blast counts >1%, patients were divided into high- and low-risk groups. The estimated 3-year survival post transplant was 38.5% for all patients. The 3-year probability of survival within the high-risk group (n = 11) characterized by the presence of at least two risk factors was 16%. Low-risk patients (n = 9) with at most one risk factor had an estimated 3-year survival of 67%. Thus, previously defined risk determinants for the outcome of allogeneic transplantation for myelofibrosis may provide useful information facilitating treatment strategies. Our data suggest that transplantation should be taken into consideration before poor prognostic variables develop.

New approaches in the treatment of myelofibrosis

Myelofibrosis with myeloid metaplasia (MMM) is a chronic clonal neoangiogenesis disorder characterized by bone marrow fibrosis and neoangiogensis with extramedullary hematopoiesis. Identification of prognostic factors associated with MMM have not impacted the treatment of the disease, which continues to be palliative with the exception of allogeneic stem cell transplantation (SCT) for potential long-term disease-free survival in selected patients. Additional insights into the pathophysiology of MMM have resulted in the use of novel therapeutic strategies in the treatment of this disease. The rationale for the investigation of these agents in MMM and the status of clinical trials with various modalities such as angiogenesis inhibitors (e.g., thalidomide), tyrosine kinase inhibitors (e.g., imatinib mesylate), farnesyl transferase inhibitors (e.g., R115777), and other agents are reviewed, in addition to the potential roles of autologous and allogeneic SCT.

Adoptive immunotherapy in chimeras with donor lymphocytes

Allogeneic stem cell transplantation has a well-defined indication in the treatment of hematological malignancies. The beneficial immune effect of allogeneic marrow transplantation has long been known, but only recently have methods been developed to separate the graft-versus-leukemia (GVL) effect from graft-versus-host disease (GVHD). Animal experiments have shown that lymphocytes from the marrow donor can be transfused without causing severe GVHD if stable chimerism and tolerance is established. First clinical studies have been preformed in patients with recurrent chronic myelogenous leukemia. In these patients complete molecular remissions were induced that persist without further maintenance treatment. These results have been confirmed in larger multicenter studies in Europe and the USA. The best results were obtained in chronic myelogenous leukemia (CML); repeated successes have been reported in relapsing acute myeloid leukemia (AML), myelodysplastic syndromes and multiple myeloma (MMY), and rare responses were reported for acute lymphoid leukemia. Contrary to animal experiments GVHD has been observed in human patients although to a lesser extent than expected in transplants not given immunosuppression. Secondly myelosuppression has been observed in patients treated with relapsing CML. In CML the incidence of GVHD could be reduced by depleting CD8+ T cells from the donor lymphocyte concentrate. Alternatively only small numbers of T lymphocytes can be transfused and in the case of failing responses, the numbers of donor lymphocytes may be increased. Results in recurrent AML have been improved by the use of low-dose cytosine arabinoside, granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor mobilized blood cells as compared to lymphocytes only. In MMY the response rate is higher than in AML, but the remissions are of limited duration in most patients. Several protocols have been designed to include preemptive donor lymphocyte transfusion in patients with a high relapse risk after transplantation. Problems remain to avoid chronic GVHD and to circumvent the immune escape mechanisms of leukemia.

Allogeneic hematopoietic stem cell transplantation for myeloproliferative disorders and myelodysplastic syndromes

Allogeneic SCT is the most effective method to achieve cure in patients with MPD and MDS. This approach is associated with significant risk of morbidity (eg, GVHD) and TRM, although the incidence and severity vary based on donor and recipient characteristics. For young patients with HLA-matched donors, SCT is the preferred therapy. Efforts to improve outcome for older patients and for patients with alternative donors have led to decreased treatment-associated complications with associated better long-term DFS.

Dose-reduced conditioning regimen followed by allogeneic stem cell transplantation in patients with myelofibrosis with myeloid metaplasia

Three patients with myelofibrosis received allogeneic stem cell transplantation after a dose-reduced conditioning regimen of busulphan (8 mg/kg), fludarabine (180 mg/m2) and antithymocyte globulin (4 x 10 mg/kg). The median age at transplantation was 51 years (range 44-58). All patients engrafted with a leucocyte count > 1.0 x 10(9)/l after a median of 18 d (range 16-20). Grade II acute skin graft-versus-host disease (GvHD) occurred in one patient. One limited and one extensive chronic GvHD was observed. All patients achieved complete haematological remission. In one patient the fibrosis resolved completely 180 d post transplant. All patients are alive 126, 466 and 764 d after transplantation.

Allogeneic blood cell transplantation following reduced-intensity conditioning is effective therapy for older patients with myelofibrosis with myeloid metaplasia

Standard myeloablative conditioning prior to allogeneic hematopoietic stem cell (HSC) transplantation has been associated with significant toxicity in patients older than 45 years of age with myelofibrosis with myeloid metaplasia (MMM). We sought to evaluate the efficacy of a reduced-intensity conditioning regimen for allogeneic HSC transplantation in this setting. A regimen consisting of fludarabine (30 mg/m2 intravenously daily for 5 days) and melphalan (70 mg/m2 intravenously daily for 2 days) followed by transplantation of filgrastim-mobilized peripheral blood cells from HLA-identical siblings was administered to 4 older patients (median age, 56 years; range, 48-58 years) with advanced MMM. All patients achieved prompt neutrophil and platelet engraftment and have experienced a significant regression of splenomegaly and bone marrow fibrosis. All now have normal bone marrow cellularity. With a median follow-up of 13 months (range, 11-19 months), all 4 patients are alive with stable full-donor hematopoietic chimerism. These results support the feasibility and effectiveness of reduced-intensity conditioning prior to allogeneic HSC transplantation for older patients with advanced MMM.

Allogeneic blood cell transplantation following reduced-intensity conditioning is effective therapy for older patients with myelofibrosis with myeloid metaplasia

Standard myeloablative conditioning prior to allogeneic hematopoietic stem cell (HSC) transplantation has been associated with significant toxicity in patients older than 45 years of age with myelofibrosis with myeloid metaplasia (MMM). We sought to evaluate the efficacy of a reduced-intensity conditioning regimen for allogeneic HSC transplantation in this setting. A regimen consisting of fludarabine (30 mg/m(2) intravenously daily for 5 days) and melphalan (70 mg/m(2) intravenously daily for 2 days) followed by transplantation of filgrastim-mobilized peripheral blood cells from HLA-identical siblings was administered to 4 older patients (median age, 56 years; range, 48-58 years) with advanced MMM. All patients achieved prompt neutrophil and platelet engraftment and have experienced a significant regression of splenomegaly and bone marrow fibrosis. All now have normal bone marrow cellularity. With a median follow-up of 13 months (range, 11-19 months), all 4 patients are alive with stable full-donor hematopoietic chimerism. These results support the feasibility and effectiveness of reduced-intensity conditioning prior to allogeneic HSC transplantation for older patients with advanced MMM.

Biology and management of idiopathic myelofibrosis

Idiopathic myelofibrosis (IMF) is a hematopoietic stem cell disorder characterized by hypercellularity of the bone marrow with an increase in abnormal megakaryocytes, varying degrees of marrow fibrosis, and extramedullary hematopoiesis. The central lesion of the IMF stem cell is not known; however, the marrow fibrosis is a polyclonal reaction to inflammatory mediators generated by the transformed clone. Historical management approaches have centered on improving the patient's blood counts in a palliative manner. Recent reports of autologous and allogeneic bone marrow transplantation (BMT) in IMF patients indicate that stable engraftment occurs easily, the marrow fibrosis is a reversible process, and a graft-versus-fibrosis effect may exist. The goals of future therapies will target marrow fibrosis and harness the graft-versus-fibrosis effect to safely and effectively treat patients with IMF.