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.

SummaryRuxolitinib (INCB018424) is the first JAK1/JAK2 inhibitor approved for treatment of myelofibrosis. JAK/STAT-signalling is known to be involved in the regulation of CD4 + T cells, which critically orchestrate inflammatory responses. To better understand how ruxolitinib modulates CD4 + T cell responses, we undertook an in-depth analysis of CD4 + T cell function upon ruxolitinib exposure. We observed a decrease in total CD3 + cells after 3 weeks of ruxolitinib treatment in patients with myeloproliferative neoplasms. Moreover, we found that the number of regulatory T cells (Tregs), pro-inflammatory T-helper cell types 1 (Th1) and Th17 were reduced, which were validated by in vitro studies. In line with our in vitro data, we found that inflammatory cytokines [tumour necrosis factor-a (TNF), interleukin (IL)5, IL6, IL1B] were also downregulated in T cells from patients (all P < 0Á05). Finally, we showed that ruxolitinib does not interfere with the T cell receptor signalling pathway, but impacts IL2-dependent STAT5 activation. These data provide a rationale for testing JAK inhibitors in diseases triggered by hyperactive CD4 + T cells, such as autoimmune diseases.In addition, they also provide a potential explanation for the increased infection rates (i.e. viral reactivation and urinary tract infection) seen in ruxolitinib-treated patients.

Key Points Transplant vs nontransplant approaches were compared in PMF patients grouped by DIPSS status. The net benefit of transplant vs nontransplant is marked in higher-risk patients.

Allogeneic stem cell transplantation (ASCT) after reduced-intensity conditioning has become a reasonable treatment option for patients with advanced myelofibrosis. The role of characteristic molecular genetic abnormalities, such as JAK2V617F on outcome of ASCT, is not yet elucidated. In 139 of 162 myelofibrosis patients with known JAK2V617F mutation status who received ASCT after reduced-intensity conditioning, the impact of JAK2 genotype, JAK2V617F allele burden, and clearance of mutation after ASCT was evaluated. Overall survival was significantly reduced in multivariate analysis in patients harboring JAK2 wildtype (hazard ratio ‫؍‬ 2.14, P ‫؍‬ .01) compared with JAK2 mutated patients. No significant influence on outcome was noted for the mutated allele burden analyzed either as continuous variable or after dividing into quartiles. Achievement of JAK2V617F negativity after ASCT was significantly associated with a decreased incidence of relapse (hazard ratio ‫؍‬ 0.22, P ‫؍‬ .04). In a landmark analysis, patients who cleared JAK2 mutation level in peripheral blood 6 months after ASCT had a significant lower risk of relapse (5% vs 35%, P ‫؍‬ .03). We conclude that JAK2V617F-mutated status, but not allele frequency, resulted in an improved survival and rapid clearance after allografting reduces the risk of relapse.

Molecular genetics may influence outcome for patients with myelofibrosis. To determine the impact of molecular genetics on outcome after allogeneic stem cell transplantation, we screened 169 patients with primary myelofibrosis (n = 110), post-essential thrombocythemia/polycythemia vera myelofibrosis (n = 46), and myelofibrosis in transformation (n = 13) for mutations in 16 frequently mutated genes. The most frequent mutation was JAK2V617F (n = 101), followed by ASXL1 (n = 49), calreticulin (n = 34), SRSF2 (n = 16), TET2 (n = 10), U2AF1 (n = 11), EZH2 (n = 7), MPL (n = 6), IDH2 (n = 5), IDH1 (n = 4), and CBL (n = 1). The cumulative incidence of nonrelapse mortality (NRM) at 1 year was 21% and of relapse at 5 years 25%. The 5-year rates progression-free (PFS) and overall survival (OS) were and 56%, respectively. In a multivariate analysis CALR mutation was an independent factor for lower NRM (HR, .415; P = .05), improved PFS (HR, .393; P = .01), and OS (HR, .448; P = .03). ASXL1 and IDH2 mutations were independent risk factors for lower PFS (HR, 1.53 [P = .008], and HR, 5.451 [P = .002], respectively), whereas no impact was observed for "triple negative" patients. Molecular genetics, especially CALR, IDH2, and ASXL1 mutations, may thus be useful to predict outcome independently from known clinical risk factors after allogeneic stem cell transplantation for myelofibrosis.

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Summary To define a prognostic model for predicting outcome of reduced‐intensity allogeneic stem cell transplantation (RIC‐ASCT) for myelofibrosis we evaluated 150 homogenously treated patients and developed a new risk score for overall survival (OS). In a multivariate Cox model for OS, only JAK2 V617F wild‐type, age ≥57 years and constitutional symptoms were independently predictive for OS (Hazard Ratio: 2·02; 2·43 and 2·80 respectively). Depending on the presence of one, two or all of these factors, HR of death was 3·08; 4·70 and 16·61 respectively (P < 0·001). This score was compared to the Lille, Cervantes, International Prognostic Scoring System (IPSS), dynamic IPSS (DIPSS) and modified European Blood and Marrow Transplantation Group (EBMT) scores. Lille score correlated significantly with OS but discriminated poorly between the intermediate and high‐risk groups (5‐year OS 56% and 51% respectively). IPSS and DIPSS correlated significantly with OS but differences between intermediate‐1 and intermediate‐2 groups were not significant (5‐year OS 78% vs. 78% and 70%, 60% respectively). Modified EBMT and Cervantes models did not predict OS post‐ASCT. In conclusion, a simple model which includes: age, JAK2 V617F‐status and constitutional symptoms can clearly separate distinct risk groups and can be used in addition to the Lille model to predict OS after RIC‐ASCT for myelofibrosis.

Transformed acute myeloid leukemia in myelofibrosis results in a median survival of less than 5 months. We identified 46 of 1048 myelofibrosis patients in the European Group for Blood and Marrow Transplantation registry who received allogeneic stem cell transplantation for acute leukemia evolving from myelofibrosis. The cumulative incidence of treatment-related mortality at 1 year was 28% (95% confidence interval, 14 to 42) and of relapse at 3 years was 47% (95% confidence interval, 31 to 63). The 3-year progression-free (PFS) and overall survival (OS) rates were 26% and 33%, respectively. The only significant factor for survival was complete remission versus no complete remission before transplantation (69% versus 22%, P = .008); however, complete remission was achieved only in 8 patients. Allogeneic stem cell transplantation can cure myelofibrosis patients transformed to leukemia.