Clonal evolution and outcomes in myelofibrosis after ruxolitinib discontinuation.

Despite significant improvements in the signs and symptoms of myelofibrosis (MF), and possible prolongation of patients' survival, some have disease that is refractory to ruxolitinib and many lose their response over time. Furthermore, patients with ≥3 mutations are less likely to respond to ruxolitinib. Here we describe outcomes after ruxolitinib discontinuation in MF patients enrolled in a phase 1/2 study at our center. After a median follow-up of 79 months, 86 patients had discontinued ruxolitinib (30 of whom died while on therapy). The median follow-up after ruxolitinib discontinuation for the remaining 56 patients was 32 months, with median survival after discontinuation of 14 months. Platelets <260 × 109/L at the start of therapy or <100 × 109/L at the time of discontinuation were associated with shorter survival after discontinuation. Of 62 patients with molecular data at baseline and follow-up, 22 (35%) acquired a new mutation while receiving ruxolitinib (14 [61%] in ASXL1). Patients showing clonal evolution had significantly shorter survival after discontinuation (6 vs 16 months). Transfusion dependency was the only clinical variable associated with clonal evolution. These findings underscore the need for novel therapies and suggest that clonal evolution or decreasing platelet counts while on ruxolitinib therapy may be markers of poor prognosis.

Approach to patients with essential thrombocythaemia and very high platelet counts: what is the evidence for treatment?

Treatment of essential thrombocythaemia (ET) is directed at decreasing the risk of complications of the disease, including arterial and venous thrombosis and bleeding episodes. Established risk factors for vascular events in patients with ET include advanced age (>60 years) and prior history of thrombosis or haemorrhage. The role, if any, of other potential risk factors, including cardiovascular risk factors, leucocytosis, high haematocrit, and JAK2 V617F has been analysed in multiple studies. The impact of thrombocytosis on the risk of vascular events has also been investigated. Many clinicians consider an elevated platelet count to be a risk factor for thrombosis or, when extreme, bleeding and utilize this as a criterion to start cytoreductive therapy. However, the relationship between thrombocytosis and vascular events is controversial and solid evidence to support the use of cytoreductive therapy in ET patients who have no other risk factors is lacking. In this review, we discuss current treatment recommendations for patients with ET, the biology underlying vascular events and risk factors thereof. We then review the evidence on the management of patients with ET and extreme thrombocytosis.

Correlation of mutation profile and response in patients with myelofibrosis treated with ruxolitinib.

Although most patients with myelofibrosis (MF) derive benefit from ruxolitinib, some are refractory, have a suboptimal response, or quickly lose their response. To identify genes that may predict response to ruxolitinib, we performed targeted next-generation sequencing (NGS) of a panel of 28 genes recurrently mutated in hematologic malignancies in a cohort of patients with MF who were treated with ruxolitinib in a phase 1/2 study. We also tested for CALR deletions by standard polymerase chain reaction methods. Ninety-eight percent of patients had a mutation in ≥1 gene. Seventy-nine (82.1%) patients had the JAK2(V617F) mutation, 9 (9.5%) had CALR mutations (7 type 1, 2 type 2), 3 (3.1%) had MPL mutations, and 4 (4.2%) were negative for all 3. ASXL1/JAK2 and TET2/JAK2 were the most frequently comutated genes. Mutations in NRAS, KRAS, PTPN11, GATA2, TP53, and RUNX1 were found in <5% of patients. Spleen response (≥50% reduction in palpable spleen size) was inversely correlated with the number of mutations; patients with ≤2 mutations had ninefold higher odds of a spleen response than those with ≥3 mutations (odds ratio = 9.37; 95% confidence interval, 1.86-47.2). Patients with ≥3 mutations also had a shorter time to treatment discontinuation and shorter overall survival than those with fewer mutations. In multivariable analysis, only number of mutations and spleen response remained associated with time to treatment discontinuation. Patients with ≥3 mutations had the worst outcomes, suggesting that multigene profiling may be useful for therapeutic planning for MF.

An accurate, simple prognostic model consisting of age, JAK2, CALR, and MPL mutation status for patients with primary myelofibrosis.

In most patients with primary myelofibrosis, one of three mutually exclusive somatic mutations is detected. In approximately 60% of patients, the Janus kinase 2 gene is mutated, in 20%, the calreticulin gene is mutated, and in 5%, the myeloproliferative leukemia virus gene is mutated. Although patients with mutated calreticulin or myeloproliferative leukemia genes have a favorable outcome, and those with none of these mutations have an unfavorable outcome, prognostication based on mutation status is challenging due to the heterogeneous survival of patients with mutated Janus kinase 2. To develop a prognostic model based on mutation status, we screened primary myelofibrosis patients seen at the MD Anderson Cancer Center, Houston, USA, between 2000 and 2013 for the presence of Janus kinase 2, calreticulin, and myeloproliferative leukemia mutations. Of 344 primary myelofibrosis patients, Janus kinase 2V617F was detected in 226 (66%), calreticulin mutation in 43 (12%), and myeloproliferative leukemia mutation in 16 (5%); 59 patients (17%) were triple-negatives. A 50% cut-off dichotomized Janus kinase 2-mutated patients into those with high Janus kinase 2V617F allele burden and favorable survival and those with low Janus kinase 2V617F allele burden and unfavorable survival. Patients with a favorable mutation status (high Janus kinase 2V617F allele burden/myeloproliferative leukemia/calreticulin mutation) and aged 65 years or under had a median survival of 126 months. Patients with one risk factor (low Janus kinase 2V617F allele burden/triple-negative or age >65 years) had an intermediate survival duration, and patients aged over 65 years with an adverse mutation status (low Janus kinase 2V617F allele burden or triple-negative) had a median survival of only 35 months. Our simple and easily applied age- and mutation status-based scoring system accurately predicted the survival of patients with primary myelofibrosis.

A Rare Case of Primary Myelofibrosis in a 14-Year-Old Patient With Congenital Asplenia.

Primary myelofibrosis (PMF) is rarely diagnosed in children, and in most cases in children younger than 3 years old. Pediatric PMF generally follows a benign course and is usually managed supportively with blood transfusions and prophylactic antibiotics for infections. We present a case of a 17-year-old girl diagnosed with PMF at the age of 14 years. A computed tomography scan performed at the time of an appendectomy showed congenital asplenism. To our knowledge, this is only the third case of myelofibrosis and congenital asplenism to be reported in the literature. Whether asplenism contributed to the development of myelofibrosis is not known.

Targeting BTK with ibrutinib in relapsed or refractory mantle-cell lymphoma.

BACKGROUND: Bruton's tyrosine kinase (BTK) is a mediator of the B-cell-receptor signaling pathway implicated in the pathogenesis of B-cell cancers. In a phase 1 study, ibrutinib, a BTK inhibitor, showed antitumor activity in several types of non-Hodgkin's lymphoma, including mantle-cell lymphoma. METHODS: In this phase 2 study, we investigated oral ibrutinib, at a daily dose of 560 mg, in 111 patients with relapsed or refractory mantle-cell lymphoma. Patients were enrolled into two groups: those who had previously received at least 2 cycles of bortezomib therapy and those who had received less than 2 complete cycles of bortezomib or had received no prior bortezomib therapy. The primary end point was the overall response rate. Secondary end points were duration of response, progression-free survival, overall survival, and safety. RESULTS: The median age was 68 years, and 86% of patients had intermediate-risk or high-risk mantle-cell lymphoma according to clinical prognostic factors. Patients had received a median of three prior therapies. The most common treatment-related adverse events were mild or moderate diarrhea, fatigue, and nausea. Grade 3 or higher hematologic events were infrequent and included neutropenia (in 16% of patients), thrombocytopenia (in 11%), and anemia (in 10%). A response rate of 68% (75 patients) was observed, with a complete response rate of 21% and a partial response rate of 47%; prior treatment with bortezomib had no effect on the response rate. With an estimated median follow-up of 15.3 months, the estimated median response duration was 17.5 months (95% confidence interval [CI], 15.8 to not reached), the estimated median progression-free survival was 13.9 months (95% CI, 7.0 to not reached), and the median overall survival was not reached. The estimated rate of overall survival was 58% at 18 months. CONCLUSIONS: Ibrutinib shows durable single-agent efficacy in relapsed or refractory mantle-cell lymphoma. (Funded by Pharmacyclics and others; ClinicalTrials.gov number, NCT01236391.)

Ruxolitinib in combination with lenalidomide as therapy for patients with myelofibrosis.

Ruxolitinib and lenalidomide may target distinct clinical and pathological manifestations of myelofibrosis and prevent therapy-related worsening of blood cell counts. To determine the efficacy and safety of the combination in patients with myelofibrosis, patients were given 15 mg ruxolitinib orally twice daily in continuous 28-day cycles, plus 5 mg lenalidomide orally once daily on days 1-21. Thirty-one patients were treated, with a median followup of 28 months (range, 12 - 35+). Due to failure to meet the predetermined efficacy rules for treatment success the study was terminated early. Simultaneous administration of ruxolitinib and lenalidomide was difficult: 20 of the 23 dose interruptions occurred within the first 3 months of therapy. Lenalidomide was interrupted in all 20 cases. Fourteen patients (45%) were completely off lenalidomide within 3 months of initiation. Responses were noted in 17 patients (55%). The median time to response was 1.8 months (range, 0.4 - 31). All responses were International Working Group for Myelofibrosis Research and Treatment-defined clinical improvement in palpable spleen size. One spleen responder also met the criteria for clinical improvement in hemoglobin. The response rate was higher (73%) among patients who did not require early dose interruption than among those who required early interruption (45%). Improvements in bone marrow fibrosis and serial reductions in lactate dehydrogenase >50% were noted in 17% and 50% of evaluable responders, respectively. Alternate approaches such as sequential dosing need to be evaluated when considering novel combination strategies for myelofibrosis. This trial was registered with clinicaltrials.gov identifier: NCT01375140.

Comorbidities predict worse prognosis in patients with primary myelofibrosis.

BACKGROUND: Comorbidities have been shown to play an important role in the prognostic assessment of several hematologic conditions; however, the role of comorbidities in primary myelofibrosis has not been studied. The objective of the current study was to evaluate the prevalence and impact of comorbidities in patients with primary myelofibrosis (PMF) using the Adult Comorbidity Evaluation-27 (ACE-27). METHODS: In this retrospective observational cohort study, a total of 349 consecutive patients with a confirmed diagnosis of PMF who presented to the study institution from 2000 to 2008 were evaluated. The authors evaluated the frequency and severity of comorbidities in these patients and assessed their impact on survival in a bivariable model that included the ACE-27 and Dynamic International Prognostic Scoring System scores as covariates. RESULTS: Approximately 64% of patients had at least 1 comorbid condition, and diseases of the cardiovascular system (63%) were most common. Comorbidities had a significant negative impact on survival (P < .001). Patients with severe comorbidities had twice the risk of death as those with no comorbidities. When stratified by demographic and clinical characteristics, comorbidities were found to be significantly associated with worse survival in patients aged < 65 years (P < .001) and those with an ECOG performance status < 1 (P < .001). In a multivariable model that included the ACE-27 and Dynamic International Prognostic Scoring System scores, comorbidities retained a significant association with shorter survival (P ≤ .001). CONCLUSIONS: The assessment of comorbid conditions in patients with PMF, particularly those who are younger and with a good performance status, has important implications for overall prognosis and treatment planning.

Lenalidomide in combination with rituximab for patients with relapsed or refractory mantle-cell lymphoma: a phase 1/2 clinical trial.

BACKGROUND: The combination of rituximab and lenalidomide has shown promise for the treatment of mantle-cell lymphoma (MCL) in preclinical studies. We aimed to identify the maximum tolerated dose (MTD) of lenalidomide when combined with rituximab in a phase 1 trial and to assess the efficacy and safety of this combination in a phase 2 trial in patients with relapsed or refractory MCL. METHODS: Patients with relapsed or refractory MCL who had received one to four previous lines of treatment were enrolled in this single-arm, open-label, phase 1/2 trial at MD Anderson Cancer Center. In phase 1, to identify the MTD of lenalidomide, four patient cohorts received escalating doses (10, 15, 20, and 25 mg) of daily oral lenalidomide on days 1-21 of each 28-day cycle. 375 mg/m(2) intravenous rituximab was also administered in four weekly doses during cycle 1 only. In phase 2, patients received rituximab plus the MTD of lenalidomide, following the same cycles as for phase 1. Treatment in both phases continued until disease progression, stem-cell transplantation, or severe toxicity. The primary efficacy endpoint was overall response (complete or partial response). The secondary efficacy endpoint was survival. We used the Kaplan-Meier method to estimate response duration, progression-free survival, and overall survival. Analysis was by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00294632. FINDINGS: 52 patients were enrolled between Feb 10, 2006 and July 30, 2009, 14 in phase 1 and 44 (including six patients who received the MTD of lenalidomide in the phase 1 portion) in phase 2. The MTD was 20 mg lenalidomide. One patient who was treated with 25 mg lenalidomide developed a grade 4 non-neutropenic infection and died. In the phase 2 portion of the study, grade 3-4 haematological toxicities included neutropenia (29 patients), lymphopenia (16 patients), leucopenia (13 patients), and thrombocytopenia (ten patients). There were only two episodes of febrile neutropenia. Among 44 patients in phase 2, 25 (57%) had an overall response: 16 (36%) had a complete response and nine (20%) had a partial response. The median response duration was 18·9 months (95% CI 17·0 months to not reached [NR]). The median progression-free survival was 11·1 months (95% CI 8·3 to 24·9 months), and the median overall survival was 24·3 months (19·8 months to NR). Five of 14 patients who had received bortezomib treatment before enrolment achieved an overall response. INTERPRETATION: Oral lenalidomide plus rituximab is well tolerated and effective for patients with relapsed or refractory MCL. FUNDING: Celgene.

Avapritinib Versus Regorafenib in Locally Advanced Unresectable or Metastatic GI Stromal Tumor: A Randomized, Open-Label Phase III Study.

PURPOSE: Primary or secondary mutations in KIT or platelet-derived growth factor receptor alpha (PDGFRA) underlie tyrosine kinase inhibitor resistance in most GI stromal tumors (GISTs). Avapritinib selectively and potently inhibits KIT- and PDGFRA-mutant kinases. In the phase I NAVIGATOR study (NCT02508532), avapritinib showed clinical activity against PDGFRA D842V-mutant and later-line KIT-mutant GIST. VOYAGER (NCT03465722), a phase III study, evaluated efficacy and safety of avapritinib versus regorafenib as third-line or later treatment in patients with unresectable or metastatic GIST. PATIENTS AND METHODS: VOYAGER randomly assigned patients 1:1 to avapritinib 300 mg once daily (4 weeks continuously) or regorafenib 160 mg once daily (3 weeks on and 1 week off). Primary end point was progression-free survival (PFS) by central radiology per RECIST version 1.1 modified for GIST. Secondary end points included objective response rate, overall survival, safety, disease control rate, and duration of response. Regorafenib to avapritinib crossover was permitted upon centrally confirmed disease progression. RESULTS: Four hundred seventy-six patients were randomly assigned (avapritinib, n = 240; regorafenib, n = 236). Median PFS was not statistically different between avapritinib and regorafenib (hazard ratio, 1.25; 95% CI, 0.99 to 1.57; 4.2 v 5.6 months; P = .055). Overall survival data were immature at cutoff. Objective response rates were 17.1% and 7.2%, with durations of responses of 7.6 and 9.4 months for avapritinib and regorafenib; disease control rates were 41.7% (95% CI, 35.4 to 48.2) and 46.2% (95% CI, 39.7 to 52.8). Treatment-related adverse events (any grade, grade ≥ 3) were similar for avapritinib (92.5% and 55.2%) and regorafenib (96.2% and 57.7%). CONCLUSION: Primary end point was not met. There was no significant difference in median PFS between avapritinib and regorafenib in patients with molecularly unselected, late-line GIST.

Genome-scale protein expression and structural biology of Plasmodium falciparum and related Apicomplexan organisms.

Parasites from the protozoan phylum Apicomplexa are responsible for diseases, such as malaria, toxoplasmosis and cryptosporidiosis, all of which have significantly higher rates of mortality and morbidity in economically underdeveloped regions of the world. Advances in vaccine development and drug discovery are urgently needed to control these diseases and can be facilitated by production of purified recombinant proteins from Apicomplexan genomes and determination of their 3D structures. To date, both heterologous expression and crystallization of Apicomplexan proteins have seen only limited success. In an effort to explore the effectiveness of producing and crystallizing proteins on a genome-scale using a standardized methodology, over 400 distinct Plasmodium falciparum target genes were chosen representing different cellular classes, along with select orthologues from four other Plasmodium species as well as Cryptosporidium parvum and Toxoplasma gondii. From a total of 1008 genes from the seven genomes, 304 (30.2%) produced purified soluble proteins and 97 (9.6%) crystallized, culminating in 36 crystal structures. These results demonstrate that, contrary to previous findings, a standardized platform using Escherichia coli can be effective for genome-scale production and crystallography of Apicomplexan proteins. Predictably, orthologous proteins from different Apicomplexan genomes behaved differently in expression, purification and crystallization, although the overall success rates of Plasmodium orthologues do not differ significantly. Their differences were effectively exploited to elevate the overall productivity to levels comparable to the most successful ongoing structural genomics projects: 229 of the 468 target genes produced purified soluble protein from one or more organisms, with 80 and 32 of the purified targets, respectively, leading to crystals and ultimately structures from one or more orthologues.

The role of thrombocytapheresis in the contemporary management of hyperthrombocytosis in myeloproliferative neoplasms: A case-based review.

Extreme thrombocytosis induces an acquired thrombotic-hemorrhagic diathesis, and left uncontrolled is a harbinger of potentially fatal vascular complications. Currently, cytoreduction with medical therapy remains the mainstay of hyperthrombocytosis management. However, it offers a less-than-ideal option in situations where a rapid reduction in platelets is urgently needed, as in the presence of vital end-organ ischemia or to ameliorate of life-threatening hemorrhage. The role of thrombocytapheresis, or plateletpheresis, in hyperthrombocytosis has become increasingly obsolete given the proactive titration of cytoreductive therapies and early identification and correction of reversible causes of reactive thrombocytosis. Despite its narrowed indications, plateletpheresis continues to offer a valuable temporizing measure in platelet count reduction before cytoreductive agents exert their maximal effect. In this context, it is important for the treating physician to be aware of the symptoms and risks associated with hyperthrombocytosis to inform best clinical practices. In this review, we discuss the role of plateletpheresis in the modern-day management of hyperthrombocytosis in patients with myeloproliferative neoplasms through a case based review of the literature. It becomes apparent throughout the discussion that the decision to perform plateletpheresis should be individualized based upon the clinical scenario, degree of thrombocytosis, available infrastructure and every patient's risk profile.

Histomorphological responses after therapy with pegylated interferon α-2a in patients with essential thrombocythemia (ET) and polycythemia vera (PV).

BACKGROUND: Pegylated interferon alfa-2a (PEG-IFN-α-2a) is a potent immunomodulating agent capable of inducing high rate of hematologic and even complete molecular remission in patients with essential thrombocythemia (ET) and polycythemia vera (PV). We recently reported results of a phase 2 trial of PEG-IFN-α-2a in 83 patients with ET and PV after a median follow-up of 83 months. Here we report an analysis of bone marrow (BM) responses in these patients. METHODS: Among 83 patients, 58 (70%, PV 25, ET 31) had evaluable BM samples. BM responses and fibrosis grading were defined according to the International Working Group for Myeloproliferative Neoplasms Research and Treatment, and the European Consensus on grading of BM fibrosis, respectively. BM was assessed prior to enrollment, and every 6-24 months while on therapy in all patients, and after therapy discontinuation in some patients. RESULTS: The median age of analyzed 58 patients was 52 years, and 29% were males. After a median follow-up of 84 months, 32 patients are still on study. Hematologic (HR) and molecular responses (MR) were seen in 93 and 69% patients, respectively. Twenty-nine patients (50%) had a BM response, including 13 (22%) with a complete BM response (BM-CR). Moreover, 13 patients (22%) have experienced complete resolution of bone marrow reticulin fibrosis. Patients with BM response had higher duration of HR and MR, and lower discontinuation rate. Furthermore, patients with BM-CR had a higher probability of complete MR. The median duration of BM-CR was 30 months, and 9 patients have maintained their BM-CR (69%), including five who have maintained their response after discontinuation of therapy. Despite this observation, the pattern of HR, MR and BM response, their durability and interrelation was heterogeneous. CONCLUSIONS: Our results show the ability of PEG-IFN-α-2a to induce complete BM responses in a subset of ET and PV patients, but its correlation with durable clinically relevant treatment benefit warrants further investigation. Trial registration This study is registered with ClinicalTrials.gov (NCT00452023), and is ongoing but not enrolling new patients.

Therapy-related myelofibrosis does not appear to exist.

There is no evidence to support the existence of therapy-related myelofibrosis.Therapy for previous malignancy has no impact on myelofibrosis prognosis.

Patients with post-essential thrombocythemia and post-polycythemia vera differ from patients with primary myelofibrosis.

Prognostic scoring systems for primary myelofibrosis (PMF) are not accurate in patients with post-essential thrombocythemia and post-polycythemia vera myelofibrosis (PET-MF; PPV-MF). Given the paucity of data describing the clinical characteristics, disease course and outcomes of these patients, we sought to describe and compare the clinical characteristics and outcomes of 755 patients with PMF, 181 with PPV-MF, and 163 with PET-MF referred to our institution between 1984 and 2013. The median follow-up was 31 months, and 56% (n=616) patients had died. Over an observation period of 3502 person-years, 11% of patients had progression to AML, with similar rates among groups. The proportion of patients with transfusion dependency (higher in PMF), leukocytosis and systemic symptoms (higher in PPV-MF), and thrombocytopenia (higher in PMF, PPV-MF) differed among groups. Median overall survival (OS) was longest in PET-MF patients (73 mo vs 45 mo (PMF) vs 48 mo (PPV-MF), p <0.001). Stratification of OS by DIPSS was only discriminatory in patients with PMF, and it failed to distinguish higher risk patients with PPV/PET-MF. In multivariate analysis, predictors of inferior OS were higher age, anemia, systemic symptoms, thrombocytopenia, and high peripheral blasts in PMF; age, anemia, and systemic symptoms for PPV-MF; and anemia, peripheral blasts and thrombocytopenia in PET-MF. Although the clinical characteristics of PPV/PET-MF patients are not substantially different from those with PMF, their outcomes differ and prognostic scoring systems for PET/PPV-MF should be improved.

Pegylated interferon alfa-2a in patients with essential thrombocythaemia or polycythaemia vera: a post-hoc, median 83 month follow-up of an open-label, phase 2 trial.

BACKGROUND: Pegylated interferon alfa-2a is an immunomodulatory agent used to treat polycythemia vera. The durability of responses and long-term safety of this drug in patients with polycythaemia vera and essential thrombocythaemia have not been reported. Here, we present long-term efficacy and safety data from a single-centre, open-label, phase 2 trial, after a median of 83 months follow up. METHODS: Patients older than 18 years who were diagnosed with essential thrombocythaemia or polycythaemia vera according to 2001 WHO criteria were eligible to enrol in our study. The initial starting dose of pegylated interferon alfa-2a was 450 µg subcutaneously once per week, but was decreased in a stepwise manner due to toxic effects to a final starting dose of 90 mg per week: three patients were started at a dose of 450 mg per week, three at 360 mg per week, 19 at 270 mg per week, 26 at 180 mg per week, and 32 at 90 mg per week. Treatment was continued for as long as the patients derived clinical benefit with reductions in dose and frequency of administration allowed at the discretion of the treating physician. Haematological responses were assessed every 3-6 months on the basis of blood counts as defined by the European LeukemiaNet critieria. The primary endpoint of the initial study was the proportion of patients with a haematological response. Complete haematological response was defined as normalisation of blood counts (for patients with essential thrombocythaemia, platelets ≤440 × 109 per L; for patients with polycythaemia vera, haemoglobin <15·0 g/L without phlebotomy) with complete resolution of palpable splenomegaly or symptoms in the absence of a thrombotic event. Data were analysed with descriptive statistics and in the intention-to-treat population. This study is registered with ClinicalTrials.gov, number NCT00452023 and is ongoing but not enrolling new patients. FINDINGS: Between May 21, 2005, and Dec 1, 2015, patients were followed up for a median of 83 months (IQR 69-94 months). Pegylated interferon alfa-2a induced haematological (66 [80%] of 83 patients) and molecular responses (35 [63%] of 55 patients) in 40 patients with essential thrombocythaemia and 43 patients with polycythaemia vera, with median durations of 66 months (IQR 35-83) and 53 months (24-70), respectively. 26 (39%) of 66 haematological responders and 25 (71%) of 35 molecular responders (with the JAK2 Val617Phe mutation) have maintained some response during follow-up: 49% maintained their best molecular response (nine of ten patients who had a complete response, five of 20 who had a partial response, and three of five who had a minor response). The incidence of major venous-thrombotic events during the study was 1·22 per 100 person-years. Overall, 18 (22%) of 83 patients discontinued therapy due to treatment-related toxicity. Although toxicity rates decreased over time, five patients had treatment-limiting grade 3 or 4 toxicities after 60 months on therapy. 32 patients are still enrolled on the study. INTERPRETATION: Pegylated interferon alfa-2a can induce durable haematological and molecular responses in patients with essential thrombocythaemia and polycythaemia vera. This drug alone and in combination with other drugs could be explored further in clinical trials. FUNDING: US National Cancer Institute.

Long-term results of a phase II trial of lenalidomide plus prednisone therapy for patients with myelofibrosis.

Lenalidomide, with or without prednisone, is an active therapy for patients with myelofibrosis (MF). We provide an update of a phase II study of lenalidomide plus prednisone in patients with MF, after median follow up of 9 years. Forty patients were enrolled in the study and all patients were evaluable for response. Response to the treatment was reevaluated using IWG response criteria published in 2013: quality of response improved over time and overall response rate was 35%. Response in splenomegaly was seen in 39% of patients and anemia response in 32%. The median time to treatment failure (TTF) in all patients was 8.2 months and the median duration of response was 34.6 months. Response was highly durable in some patients: six patients (15%) had TTF for more than 60 months (5 years) and three patients are still on the treatment beyond 109 months (9 years). Complete and partial responses were seen in one and five patients, respectively, but achieving deeper response was not necessary for the response to be durable. New clinical studies are needed to explore safe and well tolerated lenalidomide-based combination strategies for patients with MF.

Role of neoplastic monocyte-derived fibrocytes in primary myelofibrosis.

Primary myelofibrosis (PMF) is a fatal neoplastic disease characterized by clonal myeloproliferation and progressive bone marrow (BM) fibrosis thought to be induced by mesenchymal stromal cells stimulated by overproduced growth factors. However, tissue fibrosis in other diseases is associated with monocyte-derived fibrocytes. Therefore, we sought to determine whether fibrocytes play a role in the induction of BM fibrosis in PMF. In this study, we show that BM from patients with PMF harbors an abundance of clonal, neoplastic collagen- and fibronectin-producing fibrocytes. Immunodeficient mice transplanted with myelofibrosis patients' BM cells developed a lethal myelofibrosis-like phenotype. Treatment of the xenograft mice with the fibrocyte inhibitor serum amyloid P (SAP; pentraxin-2) significantly prolonged survival and slowed the development of BM fibrosis. Collectively, our data suggest that neoplastic fibrocytes contribute to the induction of BM fibrosis in PMF, and inhibiting fibrocyte differentiation with SAP may interfere with this process.