Extramedullary haematopoiesis in a patient with myelofibrosis.

Megakaryocytes are large multilobulated precursor cells which usually reside within the bone marrow and give rise to platelets. There have been rare occurrences where they have been found in peripheral blood and extramedullary tissues in conditions where the underlying mechanisms of the bone marrow have been affected. This case report discusses an unusual presentation of a man with myelofibrosis who was found to have megakaryocytes in his ascitic fluid. We have highlighted the images showing utility of combination of traditional staining methods and immunohistochemistry in combating this diagnostic dilemma.

Conventional Cytogenetic Analysis and Array CGH + SNP Identify Essential Thrombocythemia and Prefibrotic Primary Myelofibrosis Patients Who Are at Risk for Disease Progression.

The Philadelphia chromosome-negative myeloproliferative neoplasms (Ph-MPNs) are a heterogeneous group of clonal hematopoietic malignancies that include polycythemia vera (PV), essential thrombocythemia (ET), and the prefibrotic form of primary myelofibrosis (prePMF). In this study, we retrospectively reviewed the karyotypes from conventional cytogenetics (CC) and array Comparative Genomic Hybridization + Single Nucleotide Polymorphism (aCGH + SNP) in patients with ET or prePMF to determine whether the combined analysis of both methodologies can identify patients who may be at a higher risk of disease progression. We performed a comprehensive genomic review on 169 patients with a clinical diagnosis of ET (154 patients) or prePMF (15 patients). Genomic alterations detected by CC or array-CGH + SNP were detected in 36% of patients. In patients who progressed, 68% had an abnormal genomic finding by either technology. There was a shorter progression-free survival (PFS) among patients who were cytogenetically abnormal or who were cytogenetically normal but had an abnormal aCGH + SNP result. Leveraging the ability to detect submicroscopic copy number alterations and regions of copy neutral-loss of heterozygosity, we identified a higher number of patients harboring genomic abnormalities than previously reported. These results underscore the importance of genomic analysis in prognostication and provide valuable information for clinical management and treatment decisions.

Management of Patients with Early Myelofibrosis: A Discussion of Best Practices.

PURPOSE OF REVIEW: Summarize best practices for management of patients with early myelofibrosis (MF). RECENT FINDINGS: Myelofibrosis is a progressive myeloproliferative neoplasm (MPN) that generally produces burdensome symptoms and ultimately leads to worse overall survival than that observed in healthy controls or patients with other MPNs. Several Janus kinase inhibitors and various interferon formulations are now available for treatment of MF, with ruxolitinib notable for extending overall survival in addition to improving MF signs and symptoms. The chronic nature of the disease can lead some patients to avoid immediate treatment in favor of a watch-and-wait approach. This review summarizes the patient management approach taken in my practice, providing guidance and a discussion of best practices with an emphasis on the importance and clinical benefits of active treatment in early MF. In particular, a case is made to consider treatment with ruxolitinib for patients with intermediate-1 risk disease and to minimize delay between diagnosis and treatment initiation for patients with intermediate or high-risk disease.

Investigation of Serum Albumin as a Dynamic Treatment-Specific Surrogate for Outcomes in Patients With Myelofibrosis Treated With Ruxolitinib.

PURPOSE: Ruxolitinib improves splenomegaly and disease-related symptoms in most patients with myelofibrosis (MF), and it has been associated with a survival benefit in higher-risk patients with splenomegaly. Spleen volume reduction has been associated with a survival benefit in ruxolitinib-treated patients; however, its use as a surrogate is limited. We hypothesized that an anti-inflammatory response to ruxolitinib would correlate with improved patient outcomes. METHODS: We interrogated serum albumin, an acute phase reactant and marker of nutritional status in 590 patients with MF and analyzed differential trajectories of albumin on the basis of ruxolitinib treatment. Additionally, we assessed the prognostic role of baseline albumin and change in albumin. RESULTS: We found that serum albumin levels tend to decrease in patients with MF; however, this tendency is abrogated by ruxolitinib treatment. To that end, baseline serum albumin level correlates with overall survival (OS) in patients with MF, independent of the variables that comprise the dynamic international prognostic scoring system; however, this correlation is limited to ruxolitinib-naïve patients. In ruxolitinib-treated patients, the change in serum albumin after ruxolitinib treatment, rather than the baseline value, is associated with improved OS, a finding not seen in ruxolitinib-naïve patients. CONCLUSION: These findings suggest that serum albumin, a ubiquitously available laboratory value, has specific relevance in patients with MF and reflects therapeutic response to ruxolitinib.

Anemia-related response end points in myelofibrosis clinical trials: current trends and need for renewed consensus.

JAK inhibitors are the current standard of care in myelofibrosis, but many do not address and may worsen anemia; thus, anemia-related responses have traditionally been overlooked as efficacy end points in pivotal clinical trials, leading to a lack of consistency and analytic detail in their reporting. Here we apply our experiences in the phase III trials of momelotinib, a JAK1/JAK2/ACVR1 inhibitor and the first therapy indicated by the US FDA for myelofibrosis patients with anemia, to highlight how application of different criteria impacts the anemia-related benefits reported for any potential treatment in myelofibrosis. We advocate for a convention of a new expert consensus panel to bring consistency and transparency to the definition of anemia-related response in myelofibrosis.

What is this Perspective about? Anemia (too few healthy red blood cells) is common in patients with myelofibrosis. While it is becoming more common to measure the anemia benefits associated with potential treatments for myelofibrosis in clinical trials, different definitions of anemia benefit are available. This Perspective reviews these definitions, the differences between them, and why consistency and clarity in measuring anemia benefit matter. The definitions used in clinical trials of momelotinib, a treatment for patients with myelofibrosis and anemia, are also explained to show how the anemia benefit observed in these trials could have changed if different definitions were used. What does this Perspective show? Definitions of anemia benefit may include the number of red blood cell transfusions a patient receives, the amount of hemoglobin (a red blood cell protein) in their blood, or a combination thereof. Considerations such as timing, the types of patients included, and other factors are not consistent across definitions and not always clearly reported. Results when different definitions of anemia benefit were followed in the momelotinib clinical trials show that the amount of benefit observed with treatments changes depending on which definition is used. What conclusions can be drawn from this Perspective? More consistency and clarity in the definitions of anemia benefit in myelofibrosis clinical trials are needed, suggesting that a new panel of experts should come together to discuss this topic.

Neutrophil to lymphocyte ratio in myelofibrosis patients treated with ruxolitinib may predict prognosis and rate of discontinuation.

BACKGROUND: Myelofibrosis (MF) is a clonal Philadelphia chromosome negative myeloproliferative neoplasm (Ph-MPN). MF is featured by an inflammatory condition that can also drive the progression of disease. Ruxolitinib (ruxo) is the-first-in-class Jak1/2 inhibitor approved for treatment of MF, proved to reduce spleen volume and decrease symptom burden. In various malignancies neutrophil-to-lymphocyte ratio (NLR) has been indicated as predictor of progression free survival (PFS) and overall survival (OS). NLR might reflect the balance between systemic inflammation and immunity and is emerging as a prognostic biomarker in several neoplasms, including the hematological ones. METHODS: We analyzed a cohort of 140 MF patients treated with ruxo to validate baseline NLR (as a continuous variable and as a cut-off 2) as predictor of OS and of ruxo treatment discontinuation. RESULTS: We found that both baseline NLR as a continuous variable [HR 0.8 (95% CI: 0.7-0.9) (p = .006)] and NLR (<2 vs. ≥2) [HR 3.4 (95% CI: 1.6-7.0) (p = .001)] were significantly associated with OS. Censoring for patients undergone allotransplant, baseline NLR <2 was predictive of an earlier ruxo any-other-cause discontinuation [HR 3.7 (95%CI 1.7-8.3) (p < .001)]. CONCLUSIONS: NLR before starting ruxo treatment may be used as a simple and early predictor of OS and earlier ruxo discontinuation in clinical practice.

Prognostic significance of bone marrow fibrosis in diffuse large B-cell lymphoma.

INTRODUCTION: Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphomas. The aim of this study is to determine the relationship between the increase in the degree of fibrosis in the bone marrow and prognosis and mortality in newly diagnosed DLBCL. METHODS: Bone marrow biopsy of 153 newly diagnosed DLBCL patients was determined by staining with reticulin, Masson's trichrome histochemical stain, and the degree of fibrosis was determined. RESULTS: In the bone marrow biopsy performed at the time of diagnosis, bone marrow fibrosis (BMF) was observed in 70 patients. While BMF-1 was detected in 42 patients (60%), BMF-2 was detected in 25 patients (35%) and BMF-3 was detected in 3 patients (4%). As the degree of BMF increased, the median overall survival and median progression-free survival times were significantly shorter (p: 0.008), (p < 0.001). In patients with an increased degree of BMF, a significant decrease in leukocyte and neutrophil counts was observed after chemotherapy (p: 0.004). According to the results of the multivariate Cox regression model, it was determined that high NCCN-IPI risk (HR: 8.25; %95 CI: 1.09-62.52; p = 0.041) and being BMF ≥ 2 (HR: 3.75; %95 CI: 1.65-8.51; p = 0.002), increased the risk of death (p = 0.002, -2 loglikelihood = 392,553). CONCLUSION: When the literature was reviewed, it was seen that this study was the first to define that bone marrow fibrosis grade 2 and above in DLBCL is a prognostic marker associated with worse survival. In the bone marrow pathology, which is examined to detect advanced disease in DLBCL, besides lymphomatous involvement, the detection of fibrosis grade is very important.

SOHO State of the Art Updates and Next Questions | Diagnosis, Outcomes, and Management of Prefibrotic Myelofibrosis.

Prefibrotic primary myelofibrosis (prefibrotic PMF) is a myeloproliferative neoplasm with distinct characteristics comprising histopathological and clinico-biological parameters. It is classified as a subtype of primary myelofibrosis. In clinical practice, it is essential to correctly distinguish prefibrotic PMF from essential thrombocythemia especially but also overt PMF besides other myeloid neoplasms. Risk stratification and survival outcomes for prefibrotic PMF are worse than that of ET but better than that of overt PMF. Rates of progression to overt PMF and blast phase disease are also higher for prefibrotic PMF than ET. In this review we first discuss the historical context to the evolution of prefibrotic PMF as an entity, its presenting features and diagnostic criteria. We emphasize the differences between prefibrotic PMF, ET, and overt PMF with regards to presenting features and disease outcomes including thrombohemorrhagic events and progression to fibrotic and blast phase disease. Next, we discuss the risk stratification models and contextualize these in the setting of clinical management. We share our view of personalizing treatment to address unique patient needs in the context of currently available management options. Lastly, we discuss areas of critical need in clinical research and speculate on the possibility of future disease course modifying therapies in prefibrotic PMF.

[Primary myelofibrosis with double mutation in U2AF1].

A 47-year-old woman presented with subcutaneous hemorrhage. Blood tests revealed leukoerythroblastosis, anemia, and thrombocytopenia. Bone marrow biopsy led to a diagnosis of primary myelofibrosis (aaDIPSS, DIPSS-plus: intermediate-II risk). JAK2, CALR, and MPL mutations were not detected in peripheral blood, but targeted sequencing of bone marrow specimens revealed a double mutation (Q157R, S34F) in U2AF1. Allo-PBSCT was performed using an HLA-matched related donor, and post-transplantation bone marrow examination showed complete donor chimerism on day 55. Two years after allogeneic transplantation, the patient remains relapse-free. Although U2AF1 gene abnormality is known as a poor prognostic factor in primary myelofibrosis, this patient had a favorable long-term prognosis due to prompt transplantation therapy. This case highlights the importance of detailed gene mutation analysis in patients with triple-negative MF.

[Multiple myeloma with myelofibrosis at diagnosis and aggressive extramedullary relapse after autologous stem cell transplantation].

A 66-year-old man was diagnosed with symptomatic IgG-λ multiple myeloma based on the presence of anemia, thrombocytopenia, renal dysfunction, and a tumor on the right sixth rib. Bone marrow aspiration yielded a dry tap and biopsy revealed myelofibrosis grade 2. Partial response was achieved with Bd (bortezomib and dexamethasone) and VRd (bortezomib, lenalidomide, and dexamethasone). The patient received autologous stem cell transplantation, but the myeloma relapsed 3 months later, and liver tumors developed as well. DKd (daratumumab, carfilzomib, and dexamethasone) was administered, but the patient died due to disease progression. Autopsy revealed multiple extramedullary lesions in the liver, spleen, gallbladder, adrenal glands, kidneys, and multiple lymph nodes, as well as ascites.

Prognostic Impact of Bone Marrow Fibrosis and Effects of Tyrosine Kinase Inhibitors on Bone Marrow Fibrosis in Chronic Myeloid Leukemia.

BACKGROUND: Myelofibrosis is reported in around 40% of newly diagnosed chronic myeloid leukemia (CML) patients and have an important role in the pathobiology and prognosis of CML. This retrospective study aimed to evaluate the effects of bone marrow (BM) fibrosis on disease prognosis and the effects of specific tyrosine-kinase inhibitors (TKIs) on BM fibrosis in CML patients. METHODS: The study included 96 patients (>18 years) diagnosed with chronic phase (CP) CML. The clinical and demographic information were collected from the medical files. Post-treatment BM aspirate and core biopsy samples were analyzed for the presence of fibrosis and dysplasia. RESULTS: The mean age of the study patients was 52.69 years; 47.9% of the patients were female. At the onset, 53 (63.1%) patients had BM fibrosis. The difference in the overall survival of the patients with respect to BM fibrosis grades was significant (p = .001). Within the BM fibrosis grade groups, there were significant differences between grade 0 vs. grade 2, grade 0 vs. grade 3, and grade 1 vs. grade 3 (p = .005, p = .002, and p = .003 respectively) There was no significant association between the presence of BM fibrosis at the onset and not responding to first-line therapy (p = .724). Moreover, no significant association was found between the presence of BM fibrosis at the onset and molecular (p = .623) or cytogenetic response (p = .535) to first-line therapy. Additionally, the association between the type of second-line and third-line therapy and molecular response (p = .773 and p = .424, respectively) or cytogenetic response (p = .298 and p = .641) was not significant. CONCLUSION: Although BM fibrosis seems to be a crucial complication of CML with a poor prognosis, it can be reversed via TKI treatment which may result in improved survival. It might be considered to check the BM for this complication on a regular basis during therapies to test its prognostic influence in CML patients in prospective controlled trials. Further studies focused on this issue are required to utilize BM fibrosis as a candidate prognostic factor.

Diagnosis and evaluation of prognosis of myelofibrosis: a British Society for Haematology guideline

This document represents an update of the British Society for Haematology (BSH) guideline on myelofibrosis (MF) first published in 2012 and updated in 2015.1 This guideline aims to provide healthcare professionals with clear guidance on the diagnosis and prognostic evaluation of primary my-elofibrosis (PMF), as well as post-polycythaemia vera myelo-fibrosis (post-PV MF) and post-essential thrombocythaemia myelofibrosis (post-ET MF). A section on prefibrotic MF is also included. A separate BSH Guideline covers the manage-ment of MF and is published alongside this guideline.

The management of myelofibrosis: a British Society for Haematology guideline

This document represents an update of the British Society for Haematology guideline on Myelofibrosis first published in 2012 and updated in 2015 These guidelines aim to pro-vide healthcare professionals with clear guidance on stratified management for primary myelofibrosis (PMF), as well as post-polycythaemia myelofibrosis (post-PV MF) and postessential thrombocythaemia myelofibrosis (post-ET MF). A separate BSH guideline covers the diagnosis and prognostic evaluation of myelofibrosis and is published alongside this guideline

Phase 2 study of add-on parsaclisib for patients with myelofibrosis and suboptimal response to ruxolitinib: final results.

ABSTRACT: Ruxolitinib reduces spleen volume, improves symptoms, and increases survival in patients with intermediate- or high-risk myelofibrosis. However, suboptimal response may occur, potentially because of signaling via the phosphoinositide 3-kinase (PI3K)/protein kinase B pathway. This phase 2 study evaluated dosing, efficacy, and safety of add-on PI3Kδ inhibitor parsaclisib for patients with primary or secondary myelofibrosis with suboptimal response to ruxolitinib. Eligible patients remained on a stable ruxolitinib dose and received add-on parsaclisib 10 or 20 mg, once daily for 8 weeks, and once weekly thereafter (daily-to-weekly dosing; n = 32); or parsaclisib 5 or 20 mg, once daily for 8 weeks, then 5 mg once daily thereafter (all-daily dosing; n = 42). Proportion of patients achieving a ≥10% decrease in spleen volume at 12 weeks was 28% for daily-to-weekly dosing and 59.5% for all-daily dosing. Proportions of patients achieving ≥50% decrease at week 12 in Myelofibrosis Symptom Assessment Form and Myeloproliferative Neoplasms Symptom Assessment Form symptom scores were 14% and 18% for daily-to-weekly dosing, and 28% and 32% for all-daily dosing, respectively. Most common nonhematologic treatment-emergent adverse events were nausea (23%), diarrhea (22%), abdominal pain and fatigue (each 19%), and cough and dyspnea (each 18%). New-onset grade 3 and 4 thrombocytopenia were observed in 19% of patients, each dosed daily-to-weekly, and in 26% and 7% of patients dosed all-daily, respectively, managed with dose interruptions. Hemoglobin levels remained steady. The addition of parsaclisib to stable-dose ruxolitinib can reduce splenomegaly and improve symptoms, with manageable toxicity in patients with myelofibrosis with suboptimal response to ruxolitinib. This trial was registered at www.clinicaltrials.gov as #NCT02718300.

Momelotinib expands the therapeutic armamentarium for myelofibrosis: Impact on hierarchy of treatment choices.

The primary objective of treatment in myelofibrosis (MF) is prolongation of life, which is currently accomplished only by allogeneic hematopoietic stem cell transplantation (AHSCT). Determination of optimal timing for AHSCT is facilitated by molecular risk stratification. Non-transplant treatment options in MF are palliative in scope and include Janus kinase 2 (JAK2) inhibitors (JAKi): momelotinib (FDA approved on September 15, 2023), ruxolitinib (November 16, 2011), fedratinib (August 16, 2019), and pacritinib (February 28, 2022); all four JAKi are effective in reducing spleen size and alleviating symptoms, considered a drug class effect and attributed to their canonical JAK-STAT inhibitory mechanism of action. In addition, momelotinib exhibits erythropoietic effect, attributed to alleviation of ineffective erythropoiesis through inhibition of activin A receptor type-I (ACVR1). In transplant-ineligible or deferred patients, the order of treatment preference is based on specific symptoms and individual assessment of risk tolerance. Because of drug-induced immunosuppression and other toxicities attributed to JAKi, we prefer non-JAKi drugs as initial treatment for MF-associated anemia that is not accompanied by treatment-requiring splenomegaly or constitutional symptoms. Otherwise, it is reasonable to consider momelotinib as the first-line JAKi treatment of choice, in order to target the triad of quality-of-life offenders in MF: anemia, splenomegaly, and constitutional symptoms/cachexia. For second-line therapy, we favor ruxolitinib, over fedratinib, based on toxicity profile. Pacritinib and fedratinib provide alternative options in the presence of severe thrombocytopenia or ruxolitinib-resistance/intolerance, respectively. Splenectomy remains a viable option for drug-resistant symptomatic splenomegaly and cytopenia.

Essential thrombocythemia: 2024 update on diagnosis, risk stratification, and management.

OVERVIEW: Essential thrombocythemia is a Janus kinase 2 (JAK2) mutation-prevalent myeloproliferative neoplasm characterized by clonal thrombocytosis; clinical course is often indolent but might be interrupted by thrombotic or hemorrhagic complications, microcirculatory symptoms (e.g., headaches, lightheadedness, and acral paresthesias), and, less frequently, by disease transformation into myelofibrosis (MF) or acute myeloid leukemia. DIAGNOSIS: In addition to thrombocytosis (platelets ≥450 × 109 /L), formal diagnosis requires the exclusion of other myeloid neoplasms, including prefibrotic MF, polycythemia vera, chronic myeloid leukemia, and myelodysplastic syndromes with ring sideroblasts and thrombocytosis. Bone marrow morphology typically shows increased number of mature-appearing megakaryocytes distributed in loose clusters. GENETICS: Approximately 80% of patients express myeloproliferative neoplasm driver mutations (JAK2, CALR, MPL), in a mutually exclusive manner; in addition, about 50% harbor other mutations, the most frequent being TET2 (9%-11%), ASXL1 (7%-20%), DNMT3A (7%), and SF3B1 (5%). Abnormal karyotype is seen in <10% of patients and includes +9/20q-/13q-. SURVIVAL AND PROGNOSIS: Life expectancy is less than that of the control population. Median survival is approximately 18 years but exceeds >35 years in younger patients. The triple A survival risk model, based on Age, Absolute neutrophil count, and Absolute lymphocyte count, effectively delineates high-, intermediate-1-, intermediate-2-, and low-risk disease with corresponding median survivals of 8, 14, 21, and 47 years. RISK FACTORS FOR THROMBOSIS: Four risk categories are considered: very low (age ≤60 years, no thrombosis history, JAK2 wild-type), low (same as very low but JAK2 mutation present), intermediate (same as low but age >60 years), and high (thrombosis history or age >60 years with JAK2 mutation). MUTATIONS AND PROGNOSIS: MPL and CALR-1 mutations have been associated with increased risk of MF transformation; spliceosome with inferior overall and MF-free survival; TP53 with leukemic transformation, and JAK2V617F with thrombosis. Leukemic transformation rate at 10 years is <1% but might be higher in JAK2-mutated patients with extreme thrombocytosis and those with abnormal karyotype. TREATMENT: The main goal of therapy is to prevent thrombosis. In this regard, once-daily low-dose aspirin is advised for all patients and twice daily for low-risk disease. Cytoreductive therapy is advised for high-risk and optional for intermediate-risk disease. First-line cytoreductive drugs of choice are hydroxyurea and pegylated interferon-α and second-line busulfan. ADDITIONAL CONTENT: The current review includes specific treatment strategies in the context of extreme thrombocytosis, pregnancy, splanchnic vein thrombosis, perioperative care, and post-essential thrombocythemia MF, as well as new investigational drugs.

The prognostic impact of non-driver gene mutations and variant allele frequency in primary myelofibrosis.

Prognostic impact of non-MPN driver gene mutations in primary myelofibrosis. MIPSS70: Mutation-Enhanced International Prognostic Score System.

Laboratory methods of monitoring disease response after allogeneic haematopoietic stem cell transplantation for myelofibrosis.

The era of molecular prognostication in myelofibrosis has allowed comprehensive assessment of disease risk and informed decisions regarding allogeneic haematopoietic stem cell transplantation (HSCT). However, monitoring disease response after transplantation is difficult, and limited by disease and sample-related factors. The emergence of laboratory techniques sensitive enough to monitor measurable residual disease is promising in predicting molecular and haematological relapse and guiding management. This paper summarises the existing literature regarding methods for detecting and monitoring disease response after HSCT in myelofibrosis and explores the therapeutic use of measurable residual disease (MRD) assays in transplant recipients. Laboratory assessment of disease response in myelofibrosis post-allogeneic transplant is limited by disease and treatment characteristics and by the sensitivity of available conventional molecular assays. The identification of MRD has prognostic implications and may allow early intervention to prevent relapse. Further applicability is limited by mutation-specific assay variability, a lack of standardisation and sample considerations.

Real-world clinical characteristics of post-essential thrombocythemia and post-polycythemia vera myelofibrosis.

There are few prospective studies on patients with post-essential thrombocythemia myelofibrosis (PET-MF) and post-polycythemia vera myelofibrosis (PPV-MF). Therefore, we conducted a nationwide longitudinal prospective survey to clarify the clinical characteristics of these diseases. A total of 197 PET-MF and 117 PPV-MF patients diagnosed between 2012 and 2021 were analyzed. The median age at diagnosis was 70.0 years for both diseases. The time from diagnosis of ET or PV to that of MF was 9.6 and 10.4 years, respectively, with no significant difference. Patients with PPV-MF had higher hemoglobin levels and white blood cell counts than those with PET-MF, whereas those with PET-MF had higher platelet counts than those with PPV-MF. Although splenomegaly was more frequent in patients with PPV-MF at diagnosis, there was no difference in the frequency of constitutional symptoms. Ruxolitinib was the most common treatment administered to 74.6% and 83.8% of patients with PET-MF and PPV-MF, respectively. Patients with PET-MF and PPV-MF had similar prognoses, with 3-year overall survival (OS) of 0.742 in PET-MF and 0.768 in PPV-MF patients. In both diseases, leukemic transformation was the leading cause of death, followed by infection. The 3-year OS for patients with PET/PPV-MF and primary MF diagnosed during the same period was 0.754 and 0.626, respectively, with no significant difference. This survey provides real-world clinical features and prognostic data on secondary myelofibrosis in the ruxolitinib era.