Tefferi, Ayalew

Abstract Background: We have previously described a resistance to the normal process of apoptosis in neutrophils of patients with myelofibrosis with myeloid metaplasia (MMM) (Blood2003;102:11). Most recently, an activating mutation of JAK2 (V617F) has been described in approximately half of the patients with MMM as well as in variable proportion of patients with other myeloproliferative disorders (MPD). In the current study, we investigated the correlation between JAK2 V617F mutation status and neutrophil apoptosis in MMM. Methods: Neutrophils were isolated by density centrifugation from patients with MMM, other MPDs, and normal controls and assessed for apoptosis at baseline and after 24 hours in culture (IMDM with 20% sterilized fetal calf serum to simulate spontaneous apoptosis). Apoptosis was quantified using three-color flow cytometry using CD45 (to confirm leukocyte presence), annexin V (AN) (marker of apoptosis; detects aberrant externalization of phosphatidylserine during apoptosis), and propidium iodide (PI) (marker of dead cells). Mutation analysis for JAK2 V617F was performed in DNA derived from the isolated neutrophils using genomic DNA amplified by PCR, or extracted from cytogenetic pellets in archived specimens. Apoptotic rates after 24 hours in culture were correlated between patients and controls for both JAK2 mutation status and clinical parameters. Immunoblotting was performed on a subset of patients for correlation of JAK2 mutation status and downstream phosphorylation of the JAK2 target, STAT3, which transcriptionally activates several antiapoptotic genes. Results: Spontaneous neutrophil apoptosis was significantly decreased in MMM patients (n=50; median % apoptotic cells at 41%) compared to both healthy volunteers (n=9; 66%) and patients with other MPD (n=11; 53%) (p=0.002). Resistance to apoptosis in MMM correlated with both anemia (p=0.01) and the presence of the JAK2 V617F mutation (p=0.01). Furthermore, the specific abnormality was more pronounced in patients with homozygous JAK2 V617F; median % apoptotic cells of 47% for patients with wild-type allele (n=22) vs. 39% for heterozygotes (n=23) vs. 22% for homozygotes (n=5; p=0.008). The JAK2 mutation status did not appear dependent on other peripheral blood or clinical features. Neutrophils from 14 MMM patients were assessed simultaneously for both JAK2 mutation and STAT3 phosphorylation status by immunoblotting. Strong expression of phosphorylation of STAT3 was seen in all 3 homozygotes and 4 of 5 heterozygotes, but only 1 of 6 with wild-type allele (p=0.026). Conclusions: Impaired neutrophil apoptosis in patients with MMM correlates with the functional presence of JAK2 V617F in an allele-dose dependent manner and STAT3 phosphorylation. The current observation supports a pathogenetic role for the specific mutation in sustaining clonal myeloproliferation.

Abstract Post-polycythemic (PPMM) and post-thrombocythemic (PTMM) myeloid metaplasia are consensually referred to as secondary myelofibrosis (sMF). Prognostic variables in sMF are not as well defined as they are for agnogenic myeloid metaplasia (AMM). Such information is particularly crucial for management decisions in transplant-eligible patients. Accordingly, we examined the prognostic impact of several clinical and laboratory variables in 66 young patients (age < 60 years) with sMF including 37 with PPMM and 29 with PTMM. Multivariate analysis of parameters other than cytogenetics identified older age (p=0.02), anemia (hemoglobin level < 10 g/dL; p=0.007), and PPMM (p=0.009) as independent risk factors for shortened survival. However, when such analysis was restricted to patients in whom cytogenetic studies were performed (n=31), the presence of unfavorable cytogenetic abnormalities (i.e. clones other than 20q- and 13q-) became the one and only adverse prognostic factor for survival (p=0.001). Figure Figure The prognostic value of cytogenetics was independent of the Dupriez prognostic score (p=0.003). Figure Figure A similar analysis in a temporal cohort of 50 age-matched patients with AMM also identified unfavorable cytogenetics as an independent predictor of poor survival along with thrombocytopenia and anemia. The current study suggests an important prognostic role for cytogenetics in both de novo and secondary myelofibrosis.

Abstract Background: An acquired point mutations of JAK2 (V617F) was recently described in a substantial proportion of patients with myeloproliferative disorders (MPD), including myelofibrosis with myeloid metaplasia (MMM). The current study examines i) JAK2 V617F mutational status at time of leukemic transformation (LT) of MMM and its clinical correlates, ii) the possibility of changes over time in mutational status in MMM patients that have either undergone leukemic transformation (LT) or experienced disease progression. Methods: Mutation analysis for JAK2 V617F was performed in DNA derived from either peripheral blood mononuclear cells (PBMC) (i.e. fresh specimens) using genomic DNA amplified by PCR, or extracted from cytogenetic pellets in archived specimens. Fluorescent dye chemistry sequencing was performed using the same primers used for amplification. Results: The study population consisted of 68 patients including 33 patients with disease transformation into AML. i. MMM patient cohort with LT (n=33). The JAK2 V617F mutant allele was detected in 21 of the 33 patients (64%; homozygous in 6%) at the time of LT. As expected, PPMM was over-represented in the group with the mutation but the presence of the mutation affected neither the clinical presentation at time of LT or overall outcome. Furthermore, in 9 patients (7 heterozygotes and 2 with wild-type allele), archived bone marrow that was collected at a median of 23 months (range, 3–105) before LT was available and disclosed no change in mutational status. ii. MMM patient cohort with disease progression without LT (n=35; 19 AMM, 9 PPMM, 7 PTMM): Each patient in this group had at least two bone marrow or peripheral blood samples that were collected at two different time points separated by a median of 18.2 months (range (3–82). Of the total 35 patients in this group, 32 (91%) showed no change in JAK2 V617F mutational status over time including 3 patients in whom the first sample was collected before they transformed into MMM from antecedent PV or ET. In the remaining 3 patients, a switch from wild-type to heterozygous state (1 patient), and heterozygous to homozygous (2 patients), was documented after 78, 43, and 83 months, respectively. Conclusions: In most instances, JAK2 V617F mutational status in MMM remains unchanged over time including during leukemic transformation. Furthermore, the presence of the mutation in MMM-related LT does not appear to affect clinical outcome. These observations undermine the role of JAK2 V617F in either disease progression or LT in MMM.

Abstract Background: One of the utilities of molecular markers in hematological malignancies is their potential to predict response to drug therapy. Accordingly, we inquired about the effect of both cytogenetic profile and JAK2V617F mutational status on drug therapy response in myelofibrosis with myeloid metaplasia (MMM). Methods: Mutation analysis for JAK2V617 was performed in DNA derived from peripheral blood mononuclear cells, granulocytes, or both. Genomic DNA was amplified by PCR and fluorescent dye chemistry sequencing was performed using the same primers used for amplification (Levin et al. Cancer Cell2005;7:387). Abnormal cytogenetic findings were considered to be either favorable (sole 13q- or 20q- abnormalities) or unfavorable (other abnormalities) (Tefferi et al. BJH2001;113:763). Results: i. Patients and treatment: A total of 69 patients with MMM (median age 62 years, range 38–75; 47 males) received the following drugs as first-line therapy for either anemia or symptomatic splenomegaly; erythropoietin (Epo) alone or in combination with hydroxyurea (n=25), hydroxyurea alone (HU; n=17), interferon alpha (IFN; n=11), combination of thalidomide and prednisone (ThalPred; n=7), androgen preparations (Andro; n=5), and etanercept (n=4). ii. Results of cytogenetic studies and JAK2 mutation screening: Cytogenetic findings were abnormal in 35 patients (51%); favorable in 9 and unfavorable in 26. JAK2V617 mutation analysis revealed wild-type allele in 31 patients (45%) and either heterozygous (n=31) or homozygous (n=7) mutation in the remaining 38 patients (55%). iii. Correlation of response to cytogenetic/molecular markers: Overall, 17 patients (25%) achieved either a major (n=8) or minor (n=9) response in anemia from treatment with one of the aforementioned drugs. Regardless of either JAK2V617 mutational status or cytogenetic profile, treatment-induced responses in anemia were poor for IFN (0%) and HU (12%). In contrast, the best anemia responses were documented for ThalPred (57%), Andro (40%), and Epo-based therapy (32%). Among the 25 patients that received Epo-based therapy, all 3 patients with favorable cytogenetic abnormalities achieved major responses in anemia whereas such responses were seen in none of the 9 patients with unfavorable cytogenetic abnormalities and only 1 of 13 patients with normal cytogenetics (p=0.004). Furthermore, 3 of the 4 major responders were heterozygous for JAK2V617 and one carried the wild-type allele. In contrast, none of the 3 JAK2V617 homozygotes showed any type of response but all 3 also displayed unfavorable cytogenetics. None of the 7 ThalPred-treated patients carried favorable cytogenetics and yet 3 achieved major responses including one with unfavorable cytogenetics. JAK2V617 mutational status was heterozygous in 1 and wild-type in the other two. There were no major responses among the 5 Andro-treated patients despite the presence of favorable cytogenetic abnormalities in 2 patients. In order to investigate the relationship between cytogenetic profile and JAK2V617 mutational status further, we referred to an expanded database of 116 patients and found the incidence of unfavorable cytogenetics to be higher in JAK2V617 homozygotes compared to non-homozygotes (57% vs. 31%; p=0.16) Conclusion: The current study suggests clustering of favorable cytogenetic abnormalities in MMM with anemia response to Epo therapy and unfavorable cytogenetic abnormalities with homozygosity for JAK2V617 mutation.

Abstract Background: Little objective data exists regarding the impact that myeloproliferative disorders (MPDs) (essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis with myeloid metaplasia (MMM)) have on quality of life. Methods: An Internet based survey of MPD patients regarding clinical course, co-morbidities (through the Charlson Co-Morbidity Index), fatigue (through two validated fatigue instruments (FACT-AN and Brief Fatigue Inventory (BFI)), and exercise tolerance (Godin Leisure-Time Questionnaire). Results: Patient Demographics: A total of 830 MPD patients (median age 56; 60.8% male) from a broad geographic distribution (77% USA: 50 states, 30 countries, 5 continents) responded to the survey. Self reported diagnoses were PV (N=272; 33%), ET (N=221; 27%), or MMM (N=329; 40%) for a median of 5 years (range (0–53). Clinical History: 708 patients (87%) had undergone treatment for their MPD (drugs 84.6%, phlebotomy 49.5%, other 16%). A history of thrombotic (n=195, 24%) or hemorrhagic events (N=214; 26%) were frequently reported. Blood tests (available in 597 a median 1.65 months prior to survey) showed 37% were anemic (7% transfusion dependent). Additionally, 347 (44%) had splenomegaly, painful in 21%. Symptoms: Frequent symptoms reported included fatigue (90%), pruritus (57%), night sweats (54%), bone pain (48%), undesired weight loss (15%), and/or fevers (15%). 41% felt restricted in their activities, and 89 (11%) were medically disabled secondary directly to their MPD. 82% of patients felt their fatigue was linked to their MPD. Additionally 69% curtail social activity because of fatigue, and 41% need some degree of assistance with activities of daily living. Charlson co-morbidity index demonstrated 722 (87%) had minimal co-morbidities strengthening the association between fatigue and their MPD. The burden of fatigue decreased from MMM to PV to ET respectively (p=0.0002). Results from both fatigue assessment tools (FACT-AN and BFI) were highly correlated. Fatigue (FACT-AN fatigue subscale) strongly correlated with multiple MPD disease features including: anemia, bone pain, constitutional symptoms, pruritus, splenic pain, hemorrhagic events (all p<0.0001) and thrombosis(p=0.01). Additionally, currently smoking (as opposed to being a prior smoker) was highly associated with increased fatigue (p<0.0001). Interestingly, even in “asymptomatic” patients (those without anemia, splenomegaly, or thrombohemorrhagic complications (n=187)) 73% (n=128; 40% PV, 32% ET, 27% MMM; p=N.S.) described moderate to severe MPD associated fatigue. Reported physical activity was diminished (Godin Leisure Score) between MPD patients and published norms, with 38% describing minimal to no exercise. Overall, 86% stated fatigue was the major obstacle to exercise. Conclusions: Fatigue is an extremely common problem in patients with MPDs despite current therapies, and a minimal burden of co-morbidities in the majority of patients. Fatigue is also common in patients lacking advanced MPD disease features, or thrombohemorrhagic complications. Clearly, direct attempts to improve fatigue (through pharmacologic and non-pharmacologic interventions) are necessary.

Abstract BACKGROUND: Disease manifestations in myelofibrosis with myeloid metaplasia (MMM) that require therapy include anemia, thrombocytopenia, hepatosplenomegaly, and constitutional symptoms. We have previously reported on the therapeutic value of low-dose thalidomide in combination with prednisone for the treatment of both anemia and thrombocytopenia in MMM (Blood2003;101:2534), and of etanercept (tumor necrosis factor-alpha antagonist) for alleviation of constitutional symptoms (Blood2002;99(6):2252). In the current study, we investigated the value of combining all three drugs (PET). METHODS: Study eligibility criteria included a histologically confirmed diagnosis of MMM and either severe anemia (hemoglobin < 10 g/dL) or symptomatic splenomegaly. Protocol treatment was initiated with 50 mg of oral thalidomide (THAL) daily, etanercept (ETAN) 25 mg subcutaneously twice-a-week, and a three month prednisone taper starting at 0.5 mg/kg/day for the first month followed by a 50% reduction for the second months and a further 50% reduction for the third and final month of treatment with prednisone. Patients with a demonstrable clinical response after three months were able to remain on thalidomide and etanercept. RESULTS: 15 patients were enrolled to the trial (median age 66 years, range, 54–77; 14 males). Twelve patients (80%) completed the planned three cycles (i.e. 3 months) of treatment (progression (n=2) and patient choice (n=1) accounted for the withdrawals), nine (60%) patients with evidence of response continued on an additional three months of THAL/ETAN alone (of which 3 progressed prior to study completion). At enrollment, 11 patients (73%) were anemic (7 (47%) were red cell transfusion dependent), 7 (47%) were at least moderately thrombocytopenic (platelet count < 100 x 109//L), and 6 had severe constitutional symptoms (night sweats or disease related fever). Anemia response were seen in 6 (of the 11 eligible; 54%) patients (2 in the non-transfusion dependent (sustained increases of 1.5 and 4.9 g/dL hemoglobin); 4 in transfusion dependent (1 transfusion independent, 3 >50% decrease in transfusion requirements)). All thrombocytopenic patients experienced an increase in platelet counts (median 55% increase (range(10–229) with 2 returning to the normal range (>150 x 109/L)). A greater than 50% decrease in organomegaly was documented in 3 patients with splenomegaly (25% of eligible), and 1 patient with hepatomegaly (25%). Constitutional symptoms resolved, or signifcantly improved in all afflicted. Therapy overall was well tolerated with the majority of toxicities being transient. Neuropathy (grade 1; n=3; grade 2; n=1) and hyperglycemia (grade 2; n=1) were minimal. The only greater or equal to grade 3 toxicities were (grade 3: elevated bilirubin, infection, and blurred vision; grade 4: anemia). Follow-up bone marrow examination, when available, did not show post-treatment histological changes. CONCLUSIONS: This phase II study of combination therapy with thalidomide-prednisone-etanercept in patients with MMM confirms the previously recognized value of etanercept in alleviating constitutional symptoms. However, the PET regimen does not appear to be superior to thalidomide-prednisone combination in terms of therapeutic value for anemia, thrombocytopenia, or splenomegaly.

Abstract Background Estrogen-based hormone treatment (EBHT), in the form of either oral contraceptives or hormone replacement therapy, is generally felt to be associated with an increased risk of thrombosis in women with essential thrombocythemia (ET). However, there is insufficient evidence to support or refute such a concern. Methods Data was abstracted from medical records of a consecutive cohort of women with ET seen at the Mayo Clinic. Thrombotic risk was determined by the occurrence of a major thrombotic event namely myocardial infarction, angina, cerebrovascular accident, transient ischemic attack, peripheral arterial thrombosis, pulmonary embolism, or deep venous thrombosis at or after diagnosis of ET. Results i. Information regarding EBHT at or after the diagnosis of ET The study cohort included 307 women with ET (median age, 55 years; range 16–88) with a median follow-up of 133 months from diagnosis (range, 0.2–397). EBHT at or after diagnosis was documented in 93 women (30%); 59 patients were on EBHT at time of diagnosis and treatment was initiated after diagnosis in 34 patients. Among the 59 patients who were receiving EBHT at the time of diagnosis, treatment was discontinued within one month of their ET diagnosis in 17 patients but continued in the other 42 patients for a median of 48 months (range, 2–168). In the 34 patients with EBHT that was initiated after the diagnosis of ET, median treatment period was 44 months (range, 1–144). ii. Correlation between EBHT and thrombosis at diagnosis At diagnosis, major thrombosis was documented in a total of 74 patients (24%) that included 11 of the 59 patients (19%) on EBHT and 63 of 248 patients (25%) that were not receiving such therapy at the time of diagnosis (p=0.28). iii. Correlation between EBHT and thrombosis after diagnosis A total of 95 patients (31%) experienced a subsequent (i.e. post-diagnosis) thrombotic episode during the study period. These occurred in 65 of 214 patients (30%) that were not exposed to EBHT at or after diagnosis, 5 of 17 patients (29%) in whom EBHT was discontinued with the diagnosis of ET, 13 of 42 patients (31%) in whom EBHT was continued despite the diagnosis of ET, and 12 of 34 patients (35%) in whom EBHT was started after the diagnosis of ET (p=0.95). Furthermore, duration of EBHT, using a cutoff value of 1 year, did not significantly affect the incidence of thrombotic events (p=0.67). The different comparative groups were similar in age distribution as well as frequency of other cardiovascular risk factors including smoking, diabetes mellitus, hypertension, and hyperlipidemia. Conclusion The current study addresses the important issue of safety pertaining to the use of estrogen-based hormones in women with ET and did not reveal a significant alteration of thrombosis risk as a result of hormone therapy.

Abstract Background: The FIP1L1-PDGFRA fusion, an imatinib-sensitive molecular target, is detected in a subset of cases with moderate-to-severe eosinophilia (eosinophil count ≥1500/μL). Using 2 FISH strategies to detect loss of the CHIC2 locus as a surrogate marker of the FIP1L1-PDGFRA fusion, we previously found 14% of cases to be CHIC2-deleted when studying bone marrow smears from 81 adult patients with moderate-to-severe, non-reactive eosinophilia at our institution (Blood 2004, 104:3038–3045). Since then, the FISH test has been made available for routine clinical use both within our institution, and to external physicians as a mail-in test, for the workup of patients with eosinophilic disorders, including systemic mast cell disease (SMCD). Study design: FISH data, subsequent to the test’s introduction into routine clinical practice (from Nov. 2003), were retrospectively analyzed for CHIC2-deletion. Data from the initial pilot study of 81 patients was not used in this analysis (Table). The imatinib treatment analysis, however, included all CHIC2-deleted patients treated at our institution, including those from the pilot study (Table). Results: A total of 741 patients were studied in the post-pilot phase. Of these, 20 cases were found to be CHIC2-deleted, with an overall prevalence of 2.7% (Table). Of the 219 patients seen at our institution, 13 (all male) were found to be CHIC2-deleted (Table) (prevalence=5.9%), and of these, 10 have been treated with imatinib (100 mg/day starting dose) to date. Nine patients are evaluable for response - all achieved a complete clinical and histological remission (7 patients were tested by FISH post-treatment - all achieved cytogenetic remission). One patient received concomitant corticosteroids for co-morbidities and could not be evaluated for response. After a median follow-up of 24 months (range 17 to 39 months), all 9 patients continue to be in remission, with a normal eosinophil count. At last follow-up, one patient had discontinued imatinib and the others were on maintenance therapy at the following dose: 100mg/wk (n=1), 100mg BIW (n=1), 100mg TIW (n=2), 50mg QOD (n=1), and 100 mg/day (n=3). Conclusions: FIP1L1-PDGFRA prevalence in non-selected patients with eosinophilia is lower than anticipated from prior studies. Patients with FIP1L1-PDGFRA exhibit durable responses to imatinib therapy. It may be feasible to maintain some patients in remission on an empirically derived, intermittent schedule of low-dose imatinib. Pilot Data Post-pilot Data (n=741) Total Mayo samples Mayo samples Mail-in samples Number of Patients 81 138 603 822 Number CHIC2-deleted 11 2 18 31 Prevalence 14% 1.4% 3.0% 3.8% Number Imatinib treated 8 2 n/a 10

Abstract Background: The occurrence of an activating JAK2 mutation (JAK2 V617F) has been reported in a variable proportion of patients with bcr/abl-negative myeloproliferative disorders including myelofibrosis with myeloid metaplasia (MMM). In the current study, we report mutational frequencies in each of the 3 MMM variants as well as examine the prognostic relevance of the mutation in a large group of patients from a single institution. Methods: Mutation analysis for JAK2 V617F was performed in DNA derived from peripheral blood mononuclear cells (PBMC) from all study patients (n=157). Concomitant analysis was also performed in DNA derived from purified granulocytes (n=57), CD34-positive cells (n=25), and T cells (n=19). Genomic DNA was amplified by PCR and fluorescent dye chemistry sequencing was performed using the same primers used for amplification. Results: The study cohort included 157 consecutive patients with MMM including 117 with agnogenic (AMM), 22 with post polycythemic (PPMM), and 18 with post thrombocythemic (PTMM) myeloid metaplasia. The overall detection rate for JAK2 V617F in PBMC was 51% (homozygous in 5.7%) and was significantly (p=0.0002) higher in PPMM (91%; homozygous in 18%) compared to either AMM (45.3%; homozygous in 2.6%) or PTMM (38.9%; homozygous in 11.1%). In AMM (n=117), the presence of JAK2 V617F was significantly associated with an older age at diagnosis (p=0.03), and a history of both thrombosis (p=0.01) and pruritus (p=0.005). No other statistical associations were evident and the presence of the mutation did not predict leukemic transformation. Furthermore, multivariate analysis for overall survival of patients with AMM identified only age and the Dupriez prognostic score as independent prognostic factors; JAK2 V617F had no prognostic significance. Finally, the mutation was not found in T cells and its detection rate in either granulocytes or CD34-positive cells was similar to that in PBMC. Conclusion: JAK2 V617F is a myeloid lineage-specific event, its incidence in MMM is significantly higher with an antecedent history of polycythemia vera, and its presence in AMM does not affect prognosis but is associated with PV-characteristic clinical features.

Abstract Background: Conventional cytogenetic studies in myeloproliferative neoplasms (MPNs) have provided pathogenetic, diagnostic and prognostic information and in certain instances guide therapeutic decisions. It is therefore reasonable to hypothesize that a higher resolution examination of chromosomes might reveal additional changes that are scientifically as well as clinically relevant. Methods: Granulocyte DNA from 70 patients (median age 56 years, range 18–84; 43 males) with classic BCR-ABL-negative MPNs were studied: 27 with primary myelofibrosis (PMF), 22 with polycythemia vera (PV), 12 with essential thrombocythemia (ET), 6 with post-ET MF and 3 with post-PV MF. Twelve healthy volunteers were used as controls. Cytogenetic information, collected at variable times before the current study, was available in 57 patients. Samples were analyzed by comparative genomic hybridization (CGH) with a gender matched normal control using oligoarrays with either 44,000 or 105,000 oligonucleotides. Data were analyzed with CGH Analytics (Agilent). Copy number changes were considered significant (CNCs) if they were defined by 4 or more adjacent oligonucleotides spanning at least 150,000 base pairs, contained at least one gene, and were not identified in the Database of Genomic Variants. Results: Array CGH results were equivocal in 6 cases, which were therefore excluded from further analysis. Among the 12 normal controls, granulocyte DNA displayed no CNCs. The percentage of patients with CNCs was 52% for PMF, 32% for PV and 17% for ET. In addition, 2 of 6 patients with post-ET MF and 1 of 2 patients with post-PV MF displayed CNCs. There was no correlation between the occurrence of CNCs and JAK2V617F mutational status in PMF and ET. Array CGH revealed CNCs in 16 of 49 patients (33%) with normal and 7 of 8 patients (88%) with abnormal cytogenetic findings; one patient with t(2;12)(p13;q14) in 19 of 20 metaphases detected at 9 months prior to sample collection for the array CGH study displayed no CNCs. In patients with abnormal cytogenetic findings, array CGH also detected imbalances at chromosomal translocations, including t(1;6), t(9;11), and t(1;18), as well as additional abnormalities that were not detected by cytogenetic analysis. A total of 23 single occurrence CNCs were documented and included all the ET [del(2)(q31.3q32.1), del(10)(q11.21q11.22)] and post-ET MF [del(2p12), del(Xq12)] associated CNCs. In contrast, several specific abnormalities were shared between PV and PMF including del(6p22) and dup(15q11.2). As expected, del(13q) and del(20q) abnormalities were recurrent in PMF. Conclusions: Conventional cytogenetic analysis underestimates the extent of genomic gains and losses in BCR-ABL-negative MPNs. The current study suggests that oligonucleotide array CGH is more sensitive to detect small genomic alterations and we are currently studying higher resolution arrays in a larger group of patients to detect additional genomic alterations as well as assess overall clinical utility. The current data also suggest that chromosomal translocations are commonly associated with imbalances.