Tefferi, Ayalew

Abstract Background : Current risk stratification for thrombosis in essential thrombocythemia (ET) utilizes age >60 years, history of thrombosis, JAK2V617F mutation and cardiovascular risk factors (Barbui, Blood 2012;26:5128). Thrombosis history is also predictive of inferior overall survival (OS) in ET (Passamonti, Blood 2012;6:1197). However, whether or not the prognostic impact of thrombosis in ET is contributed by arterial versus venous thrombosis is unclear. Methods: More than 45,000 patient charts with "thrombocytosis" were reviewed to identify those who met either PVSG (older patient cohort) or WHO criteria for diagnosis of ET. Details of type of thrombotic events were obtained by careful review of the medical record. A subset of patients was molecularly annotated for the JAK2, CALR and MPL mutations. OS was calculated from time of initial diagnosis to the time of last follow-up or death. Thrombosis-free survival (TFS) was calculated from the time of diagnosis of ET to the time of development of thrombosis or last follow up or death, in patients censored for thrombosis. Conventional statistics was utilized for all analyses. Results :Patient characteristics: A total of 610 patients met the above-stipulated criteria (median age 57 years; 61% females). 76 patients (12%) had thrombosis documented either prior to or at diagnosis of which 50 patients (66%) experienced arterial events. 302 patients were screened for JAK2/CALR/MPL mutations with a frequency of 53.5%, 31%, and 3% respectively, while12.5% were "triple-negative".Impact of thrombosis history on OS: At a median follow-up of 8.9 years (range: 0-43.6 years), 185 (30%) deaths were documented. Themedian OS for the entire cohort was 20 years. On univariate survival analysis, the predictors of inferior OS included: age ≥60 years (p<0.001), leukocyte count ≥11 x 10(9) (p<0.001), male sex (p=0.0002), thrombosis before or at diagnosis (p=0.01), and presence of the JAK2V617F mutation (p=0.03). All but JAK2 V617F (p=0.64) remained significant on multivariable analysis. When arterial and venous events were considered separately, in univariate analysis, only arterial (p<0.001) but not venous (p=0.387) thrombotic events retained significance. The significant prognostic contribution, to survival, of arterial thrombosis history was sustained (p=0.02) during multivariable analysis, that included age ≥ 60 years (p=<0.001), leukocyte count ≥11 x 10(9) (p=0.001), and male sex (p=0.001) on OS.Impact of thrombosis history on TFS: A total of 84 (14%) patients experienced thrombotic events during follow-up amongst which 60 (71%) experienced arterial thrombosis. On univariate analysis the predictors of inferior TFS included: age ≥ 60 years (p=0.016), leukocyte count ≥11 x 10(9) (p=0.001), thrombosis before or at diagnosis (p<0.001), and presence of the JAK2V617F mutation (p=0.002). On multivariable analysis, thrombosis before or at diagnosis (p<0.001), along with leukocyte count ≥11 x 10(9) (p=0.03), and presence of the JAK2V617F mutation (p=0.01) remained significant; the significance of age ≥60 years became borderline (p=0.07). When arterial and venous thrombosis were analyzed separately, only arterial (p<0.001), but not venous (p=0.48), thrombosis history was significantly associated with inferior TFS. The factors that predicted worse outcome with TFS included arterial thrombosis at or before diagnosis (p<0.001), leukocyte count ≥11 x 10(9) (p=0.03) and presence of the JAK2V617F mutation (p=0.01); the significance of age ≥60 years became borderline (p=0.13). Conclusions : The prognostic impact of thrombosis in ET, in terms of both overall and thrombosis-free survival, might be attributed to only arterial but not venous thrombotic events. The current study also confirms the independent prothrombotic role of JAK2V617F mutation in ET and suggests an additional role for leukocytosis. Disclosures Barbui: Novartis: Speakers Bureau.

Abstract Background Imetelstat is a 13-mer lipid-conjugated oligonucleotide that targets the RNA template of human telomerase reverse transcriptase. A pilot study of imetelstat therapy in myelofibrosis showed the induction of complete (CR) or partial remissions, as well as molecular remissions, in a subset of patients (Blood. 2014;124:634). In the particular study, CR was significantly higher in patients with SF3B1 or U2AF1 spliceosome mutations, which provided the rationale for the current study; spliceosome mutations are closely associated with refractory anemia with ring sideroblasts with (RARS-T) or without (RARS) thrombocytosis (Leukemia. 2013;27:1826). Methods Diagnosis of RARS and RARS-T was according to WHO criteria (Blood. 2009;114:937). Study patients were treated with a 2-hour intravenous infusion of 7.5 mg/kg imetelstat (Janssen Biotech Inc., Horsham, PA, USA) every 4 weeks. Drug activity was monitored by both formal response criteria (Blood. 2006;108:419) and effect on spleen size, thrombocytosis and leukocytosis. Adverse events (AEs) were monitored by Common Terminology Criteria for Adverse Events (Version 4.03). Laboratory correlative studies included analysis of mutations. Results Accrual to this signal study is now complete and median time from study registration, as of 5/10/2015, was 17.1 months (range 16.1-20.1). Among the 9 study patients, 5 had RARS-T, 3 had RARS and one had "MDS/MPN overlap". Median age was 70 years (78% males). 8 (89%) patients were transfusion-dependent. One patient (RARS-T) had marked splenomegaly (palpable at 16 cm). Three patients each had leukocytosis and thrombocytosis. Seven (78%) patients had received prior treatments, including erythropoiesis stimulating agents in 6 (67%). Baseline international MDS prognostic scoring system scores were intermediate-1 (n=7) and intermediate-2 (n=2). Karyotype was normal in all but one patient with loss of Y chromosome. Drug activity Median duration of treatment with imetelstat was 13.7 months (range 6.6-17.9). Three (38%) patients achieved transfusion-independence (TI) during treatment, defined as not requiring transfusions for at least 8 weeks; 2 had RARS and one RARS-T. The median time to TI was 11 weeks (range 9-14) and the median TI duration was 28 weeks (range 9-37). One of the 3 "TI" patients also had resolution of leukocytosis and thrombocytosis. A 4th patient experienced >50% decrease in palpable spleen size as well as a decrease in transfusion need. In addition, imetelstat induced normalization of counts in two additional patients with thrombocytosis and leukocytosis. As of 5/10/2015, 4 (44%) patients remain on active treatment and one death had been recorded (deemed unrelated to imetelstat). The 5 treatment discontinuations were: death during active therapy, discovery of second malignancy, progression into acute leukemia and insufficient response (n=2). Safety Treatment-emergent grade 4 neutropenia and thrombocytopenia were seen in 2 (22%) and 1 (11%) patients, respectively; neutropenia, and thrombocytopenia were seen in 4 (44%), and 2 (22%) patients. Grade 3 anemia was seen in 6 (67%) of the patients, however baseline grade 2 anemia was noted in 2 (22%) and grade 3 in 3 (30%) patients. None of the grade ≥3 hematologic toxicities lasted ≥4 weeks.. The following grade 3 non-hematologic events occurred in 1 subject: aspiration, fatigue, and lipase increase and a patient with pre-existing cardiovascular disease history experienced a grade 5 heart failure. Treatment-emergent liver function test abnormalities affected: ALT (grade 1 56%/grade 2 11%), AST (grade 1 56%/grade 2 11%), ALP (grade 1 33%), and total bilirubin (grade 2 11%). For patients that discontinued treatment with imetelstat, these events were mostly reversible. Mutation studies Patients were screened for mutations involving JAK2, SF3B1, U2AF1 and SRSF2. Three patients were mutated for JAK2, 7 for SF3B1 (4 K700E, 2 H662Q, one K666N) and one for U2AF1 (Q157P). All three patients with "TI" (H662Q, K700E, K666N) and the 4th patient with spleen response (K700E) were SF3B1mutated. Post-treatment analysis showed no effect of imetelstat on mutations. Conclusions Treatment with imetelstat may offer clinical benefit in patients with RARS or RARS-T with generally acceptable safety profile and warrants further clinical investigation. Disclosures Al-Kali: Celgene: Research Funding. Wan:Janssen Research & Development: Employment, Equity Ownership.

Abstract Philadelphia-negative Myeloproliferative Neoplasms (MPN) include Polycythemia Vera (PV), Essential Thrombocythemia (ET) and Myelofibrosis Primary (PMF) and secondary to PV and ET (PPV-, PET-MF); included are also some less characterized entities defined as unclassified MPN (U-MPN). Risk of arterial and venous thrombosis is increased in MPN patients, and thrombosis is one of most important causes of mortality and morbidity. The risk of venous thrombosis in unusual sites, such as splanchnic vessels (SVT), is particularly associated with MPN; SVT can lead to complications such as portal hypertension, esophageal and gastric varices, ascites and hepatic failure. A recent meta-analysis reported that a MPN is the underlying cause of portal vein thrombosis in 31.5% and of Budd Chiari syndrome in 40.9% of cases (Smalberg, 2012). A significant association of SVT with JAK2V617F mutated MPN was reported (Dentali, 2009) but study of other correlations has been hampered by heterogeneity of available patient cohorts comprising relatively small number of cases. We conducted a retrospective multicenter study collecting clinical and biological data of patients (pts) with SVT associated with MPN diagnosed according to WHO2008 criteria, aiming to describe patients’ characteristics, trends and prognostic factors, and their potential implications for clinical practice. Data were collected from 15 international hematology centers in the framework of IWG-MRT. We collected 475 cases of pts with portal, splenic or mesenteric vein thrombosis (75.2%) or Budd Chiari syndrome (24.8%) associated with MPN. In 32% of cases, simultaneous involvement of portal (69.1% of total thrombosis), splenic (30.5%) and mesenteric (25.3%) veins occurred, and in 1.7% they were associated with Budd Chiari syndrome. Frequency of MPN subtype: 38.1% ET (n=181), 34.9% PV (n=166), 16.2% MF (n=77), 10.8% U-MPN (n=51). Median follow-up 87.9 mo (range 0.5-430); female 61.3% (n=292; P<0.0001 vs male); median age at MPN diagnosis (dg) 44.4 y (range 12-90), at SVT dg 44.9 y (range 17-85). In 229 cases (48%) MPN and SVT dg were coincident, while in 104 (22%) SVT occurred before MPN dg (median 40 mo, range 5-335) and in 129 (27%) during MPN follow up (median 79 mo, range 5-394). JAK2V617F mutational status is available for 361 pts: 99% PV, 84.7% ET, 88.1% PMF and 92.9% U-MPN pts were JAK2V617F positive, with a mean allele burden of 56±27.4%, 33.1±25.5%, 39.3±19.4% and 23.8±11.9%, respectively. Erythropoietin-independent colonies (EEC) were present at diagnosis in 80/110 evaluated cases (72.7%), 38/47 PV (84.4%), 32/45 ET (71.1%), 8/11 PMF (72.7%) and 2/7 U-MPN (28.6%). A concurrent thrombophilic state was found in 38.9% of cases. A 12.3% of pts experienced a recurrence of SVT after a median of 29 mo (range 1-378.3) and 35.8% developed thrombosis in other sites (17.7% arterial, 19.3% venous). Esophageal varices were found in 70.6% from which 31.9% bled. MF transformation occurred in 32/166 PV (19%) and in 23/181 ET (13%) pts, with median time to progression of 122.3 mo (range 5.4-377.3) and 125.1 mo (range 39.3-255.3), respectively. Evolution to acute leukemia (AL) occurred in 12 pts (2.7%), of which 2 PMF, 6 PV and 4 ET. In 3 PV and 1 ET pts a PPV and PET-MF transformation occurred before AL. After SVT, 77% of pts received anticoagulation, 23.5% antiaggregant therapy and 1.5% both; 68.8% received cytotoxic drugs, 11.4% of pts were treated with trans jugular porto-systemic shunt. No differences in survival were noted with these approaches. Beta blocker therapy was used in 48.5% of pts and correlated with improved survival (p=0.041) At last follow up 70/473 pts (14.8%) died; causes of death are evolution to AL (16.4%), other cancers (14.5%), disease progression without AL (12.7%), SVT (10.9%), hepatic failure and venous thrombosis other than SVT (9.1% each), heart failure and arterial thrombosis (7.3% each), hemorrhage (5.5%), renal failure and infection (3.6% each). After 10 y follow up 8/166 PV (5%), 14/181 ET (8%), 14/77 PMF (18%) and 1/51 U-MPN (1.96%) pts died (p<0.01). Survival was significantly affected by occurrence of thrombosis other than SVT (p<0.0001) but not recurrence in splanchnic vessels (p=0.068). This large study confirms the strong association between JAK2V617F-mutated MPN and SVT and identifies the category of U-MPN as the prognostically more favorable; thrombosis at sites outside the splanchnic vasculature remains the leading cause of death. Disclosures: No relevant conflicts of interest to declare.

Abstract Background The Dynamic International Prognostic Scoring System-plus (DIPSS-plus) uses eight adverse factors to predict survival in primary myelofibrosis (PMF): age >65 years, hemoglobin <10 g/dL, leukocytes >25 x 109/L, circulating blasts 31%, constitutional symptoms, red cell transfusion need, platelets <100 x 109/L and unfavorable karyotype (J Clin Oncol. 2011;29:392). The latter two also predicted leukemic transformation. Most recently, an international study of 879 PMF patients identified ASXL1, SRSF2, EZH2 and IDH1/2 mutations as inter-independent predictors of shortened overall or leukemia-free survival (Leukemia 2013Apr 26 doi: 101038/leu2013119. 2013). Molecular prognostication is now well established for acute myeloid leukemia with normal karyotype (NK). There is currently little information on clinical or molecular prognostication in NK-PMF. Methods Diagnosis of PMF was according to WHO criteria. The study population included all referrals to the Mayo Clinic, Rochester, MN, USA or the University of Florence, Florence, Italy. Information on clinical and laboratory parameters and karyotype was available in all study patients, at time of referral, which coincided with time of sample collection for mutation screening. The current study considered only those patients with NK-PMF. ASXL1, EZH2, SRSF2, IDH1/2 and JAK2 mutations were performed on variable number of patients depending on bone marrow or granulocyte DNA availability. Clinical parameters examined for prognostic relevance included those listed for DIPSS-plus, less unfavorable karyotype. Results A total of 690 patients with NK-PMF patients were studied. Median age was 65 years (14-89). The percentage of patients with age >65 years was 48%, red cell transfusion dependent 35%, hemoglobin <10 g/dL 49%, platelets <100 x 10(9)/L 19%, leukocyte count >25 x 10(9)/L 15%, circulating blasts ≥1% 49% and constitutional symptoms 33%. At a median follow-up of 29 months, 351 (51%) deaths and 39 (6%) leukemic transformations were recorded. Mutational frequencies and clinical correlates The respective frequencies (mutated/number of patients studied) of JAK2V617F, ASXL1, EZH2, SRSF2 and IDH1/2 mutations were 60% (284/473), 34% (72/214), 8% (14/179), 15% (37/249) and 5% (14/262). There was no significant association between JAK2V617F and any one of the aforementioned mutations. Inter-mutation association was evident only between SRSF2 and IDH1/2 (p=0.0005). Each one of the DIPSS-plus risk parameters was examined for correlation with a specific mutation: ASXL1 was associated with leukocyte count >25 x 10(9)/L (p<0.0001) and circulating blasts ≥1% (p=0.0005); EZH2 with leukocyte count >25 x 10(9)/L (p=0.008); and SRSF2 with age >65 years (p=0.0007), transfusion need (p=0.04) and hemoglobin <10 g/dL (p=0.03). JAK2V617F was associated with age>65 years (p=0.003) and leukocyte count >25 x 10(9)/L (p=0.02). Predictors of overall and leukemia-free survival In univariate analysis, all 7 DIPSS-plus parameters, as well as ASXL1, EZH2, SRSF2 and IDH1/2 mutations showed significant association with shortened survival: When each of these analyses was adjusted for age, all except constitutional symptoms and SRSF2 mutations retained their significance. Multivariable analysis of the six age-independent DIPSS-plus variables identified all but transfusion-need as independent predictors of inferior survival. A similar analysis restricted to mutations identified ASXL1 and EZH2 as being independently adverse. When both mutations and DIPSS-plus variables were included in the multivariable model, only four parameters remained significant: age >65 years (HR 4.2; p<0.0001), platelets <100 x 10(9)/L (HR 3.4; p<0.0001), ASXL1 mutations (HR 2.2; p=0.0001) and EZH2 mutations (HR 2.7; p=0.001). A similar analysis identified SRSF2 mutations (HR 5.9; p=0.0003) and platelets <100 x 10(9)/L (HR 4.3; p=0.005) as the only predictors of leukemia-free survival. Conclusions In NK-PMF, molecular markers might be prognostically more useful than conventional models that rely on clinical features. In the current study, thrombocytopenia was the only clinical variable, other than age, with additional value to molecular prediction of survival and leukemic transformation. Disclosures: No relevant conflicts of interest to declare.

Abstract Background Chronic myelomonocytic leukemia (CMML) is a clonal stem cell disorder with overlapping features between myelodysplastic syndromes and myeloproliferative neoplasms. Numerous models exist for CMML prognostication, with more recent studies suggesting (JCO 201; 31:2428) or refuting (Leukemia 2013; 27:1504) the prognostic contribution of ASXL1 mutations. Furthermore, SETBP1 mutations were recently shown to be associated with shortened overall survival (OS) in CMML (Leukemia 2013; 10:1038). In the current international study, we examine these issues in a larger cohort of 431 patients. Methods 431 patients with WHO-defined CMML were included in the study. 235 (55%) were seen at the Mayo Clinic from 1997 through 2012. The remainders were from the French CMML registry (JCO 201; 31:2428). All patients underwent bone marrow (BM) examination and cytogenetic evaluation at diagnosis. DNA analysis for spliceosome component mutations (SRSF2, SF3B1 and U2AF1), ASXL1 and SETBP1 mutations were carried out on BM specimens obtained at diagnosis. In order to address the aforementioned discrepancy regarding the prognostic impact of ASXL1 mutations, relevant analyses in the Mayo cohort were first performed with and without inclusion of missense ASXL1 mutations. ASXL1 mutations from the French cohort did not include missense mutations. We evaluated the prognostic relevance of ASXL1 and SETBPI mutations, as well as several other clinical and laboratory parameters including those previously identified by the MDAPS (Blood 2002;99:840) the Spanish cytogenetic risk stratification (Haematologica 2011;96:375), and the Mayo prognostic model (Leukemia 2013;27;1504). Results Among the 431 study patients, 286 (66%) were males and median age was 73 years (range, 17-93 years). There were 368 (85%) patients with CMML-1 and the remainder had CMML-2. At a median follow-up of 23 months, 260 (60%) deaths and 70 (16%) leukemic transformations were documented. Median survivals were 38 months for CMML-1 and 24 months for CMML-2 (p=0.11). Mutational frequencies were 44% (173/390) for SRSF2, 6% (23/379) for SF3B1, 7% (27/387) for U2AF1, 38% (164/411) for ASXL1 (excluding missense mutations), and 5% (21/431) for SETBP1. Risk stratification was, based on i) Mayo prognostic model: 172 (40%) high, 151 (35%) intermediate and 94 (25 %) low risk, ii) MDAPS: 15 (3%) high, 73 (17%) intermediate-2, 125 (29%) intermediate-1 and 218 (50%) low risk and iii) Spanish cytogenetic stratification system: 316 (73%) low, 43 (10%) intermediate and 50 (12%) high risk. In the Mayo cohort, univariate analysis revealed that the exclusion of missense mutations changed the prognostic impact of ASXL1 mutations from non-significant (p=0.08) to significant (p=0.001). Accordingly, all subsequent analyses excluded missense ASXL1 mutations. In univariate analysis, lower hemoglobin (p<0.0001), lower platelet count (p=0.0027), higher absolute monocyte count (AMC) (p<0.0001), higher absolute lymphocyte count (ALC) (p=0.0002), circulating immature myeloid cells (IMC) (P<0.0001), cytogenetic risk stratification (p<0.0001) and ASXL1 mutations (p<0.0001) were significant for OS. In multivariable analysis, lower hemoglobin (p=0.0001; RR 2, 99% CI 1.6-2.6), lower platelet count (p=0.002; RR 1.5, 99% CI 1.2-1.9), higher AMC (p=0.0002; RR 2.2, 99% CI 1.6-3.1) and ASXL1mutations (p=0.0009; RR 1.9, 99% CI 1.5-2.4) retained their independent negative prognostic impact. Similarly, in univariate analysis, leukemia-free survival (LFS) was negatively affected by age (p=0.0015), lower hemoglobin (p=0.0002), lower platelet count (p=0.0002), higher AMC (p<0.0001), higher ALC (p=0.0001), circulating IMC (p<0.0001), BM blasts (p<0.0001), and cytogenetic risk stratification (p=.0002). ASXL1 (p=0.17) and SETBP1(p=0.87) mutations were not found to be significant. In multivariable analysis, lower platelet count (p=0.0005), higher AMC (P=0.0042), circulating IMC (P=0.008) and cytogenetic risk stratification (p=0.009) retained their independent negative prognostic impact. Conclusions In the current international study of a large cohort of patients with CMML, we confirm and clarify the independent prognostic relevance of ASXL1 mutations. The relatively high frequency of ASXL1 mutations in CMML warrants its inclusion in contemporary prognostic models. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 2911 Poster Board II-887 BACKGROUND: Pomalidomide (POM) is an immune modulatory drug (IMiD® Immunomodulatory compound) recently shown to improve anemia in subjects with myelofibrosis (MF) in an adaptive phase-2 trial (0.5 mg or 2.0 mg/d with or without prednisone; Tefferi et. al. JCO 2009)). There were no dose limiting toxicities (DLT) observed. No other MF-features (splenomegaly, fibrosis) were identified/improved even at the highest dose. We performed a subsequent dose-escalation trial to determine whether higher doses of POM are effective and well tolerated. METHODS: The trial was classic 3 × 3 design on pts with symptomatic MF (anemia and/or symptomatic splenomegaly). POM was started at dose of 2.5 mg/days (d) for 21 d every 28 d. Dose increased in cohorts by 0.5 mg/d were done if no subject had a DLT (≥grade-4 hematologic toxicity, ≥grade-3 febrile neutropenia or ≥grade-3 non-hematologic toxicity) in cycle-1. Subsequent cohorts were enrolled until the maximum tolerated dose (MTD) was reached (dose level before that resulting in DLT in >1 of 6 subjects). In the phase 2 portion, subjects were treated at the MTD, those without response at the MTD after 3 cycles were lowered to the minimal effective dose (MED) of 0.5mg/d. RESULTS: Subjects: 19 subjects with MF were enrolled 06/2008-03/2009. 14 had primary MF, 3 post-polycythemia vera MF, and 2 post-essential thrombocythemia MF. Median age was 67 y (range, 43-83 y), 11 were female (58%). 16 had a JAK2-V617F mutation. 11 were RBC-transfusion–dependent (58%). 16 subjects had palpable splenomegaly, median 12.5 cm below the LCM (range, 1-26 cm). Median time since diagnosis was 24 mo (range, 1-173 mo). 15 were considered intermediate-high risk by IWG-MRT IPSS (Cervantes et al, Blood, 2009). Phase-1: 3 subjects each were enrolled at the 2.5 mg/d, 3.0 g/d, and 3.5 g/d mg dose cohorts. A DLT (bone marrow suppression) was seen at the 3.5 mg/d level. 3 additional subjects received 3.0 mg/d level cohort confirming this dose as the MTD. Phase-2: 10 additional subjects were enrolled at the MTD of 3.0mg/d. No improvement in anemia was seen, possibly because of bone marrow suppression. Consequently, the dose was decreased to 0.5mg/d in 7 subjects (2 remain on 3.0mg). 9 subjects remain on POM (all but 2 at 0.5mg/d. 104 cycles have been given (median, 4/ subject; range, 2-11). 10 subjects, all at ≥2.5mg/d discontinued because of lack of response/ withdrawal of consent (N=5), progression (N=4) or unrelated worsening co-morbidities (N=1). Toxicity: Dose-related bone marrow suppression was the main toxicity. 10/19 subjects had grade-3/-4 neutropenia (N=8) and/or thrombocytopenia (=3) and was only observed at doses ≥2.5mg/d. No substantial bone marrow suppression at 0.5m/d. Non-hematologic toxicity was uncommon at any dose level with grade-3 fatigue at 3.0mg/d in 1 subject. Efficacy: There was clinical benefit in 9 subjects. 7 subjects achieved an IWG-MRT response (Tefferi et al, Blood, 2006) including clinical improvement (CI) in anemia (N=6; rbc-transfusion-independence or hemoglobin increase >2g/dL for ≥2 mo) and/or splenomegaly (N=2; ≥50% reduction of palpable component for ≥2 months). 2 subjects had improved anemia below the IWG-MRT CI-threshold. Clinical benefit occurred after a median of 3.8 mo (range, 2.1-9.2 mo), and only after reduction to 0.5mg/d in 7 responders including both with spleen responses. There were 2 responses amongst 11 subjects receiving ≥2.5 mg/d compared to 7 of 8 subjects receiving '1.0mg/d. These responses occurred a median of 1 cycle after dose reduction (1-3 months). Responses were durable: 8 of 9 responders continue on-study. CONCLUSIONS: In subjects with myelofibrosis, POM doses ≥2 mg/d are associated with moderate to severe bone marrow suppression. Response occurred at doses ≥2 mg/d primarily after dose reduction to 0.5 mg/d where bone marrow suppression was infrequent. The authors suggest 0.5 mg/d as the preferred doses for a phase-3 trial. Disclosures: Litzow: Enzon: Honoraria, Research Funding.

Abstract Abstract 2910 Poster Board II-886 Background: Polycythemia vera (PV) and primary myelofibrosis (PMF) are stem cell-derived myeloproliferative neoplasms characterized clinically by increased red cell volume and bone marrow fibrosis, respectively. Phlebotomy is the cornerstone of treatment in PV whereas hydroxyurea has been the traditional drug of choice in both PV and PMF. Over the last 20 years, several new treatment approaches have been introduced and promoted (e.g. interferon-alpha, anagrelide, thalidomide, allogeneic stem cell transplantation) but their benefit in terms of survival has not been confirmed in controlled studies. Methods: Study patients were recruited form the Mayo Clinic database for myeloproliferative neoplasms. Diagnosis was based on 2001 WHO criteria. Follow-up information was updated in July, 2009. In order to assess changes in survival over time, patients were stratified into two groups by year-of-diagnosis: 1970-1990 and 1991-2005. Survival analysis was performed by the Kaplan-Meier method and comparisons made by the log-rank test. Cox regression model was used for multivariable analysis. Results: 652 patients were studied, including 314 with PMF (median age 57 years, range 18-88; 193 males) and 338 with PV (median age 63 years, range 18-93; 183 males). Overall median survivals were 6.5 years for PMF and 12.2 years for PV (p<0.0001); ten- and twenty-year survival rates were 37% and 13% in PMF and 60% and 18% in PV (Figure). Both the International Prognostic Scoring System for PMF (IPSS; Cervantes et al. Blood 2009;113:2895) and the age/leukocyte count-based PSS for PV (Gangat et al. BJH 2007;138:354) were validated in the current series of patients. Considering all patients, there was no significant difference in survival when either PMF (p=0.91) or PV (p=0.73) patients were stratified according to year-of-diagnosis (Figure); median survivals were 4.7 and 6.6 years in PMF patients diagnosed 1970-1990 (n=54) and 1991-2005 (n=260), respectively; the corresponding median survival figures for PV were 11.8 (n=170) and 12.2 (n=168) years. These results did not change when adjusted for age and sex and, in PV, for age/leukocyte count-based PSS. In PMF, however, borderline significance (p=0.05) was noted when IPSS scores were introduced into the Cox model with further analysis showing improved survival in Int-2/high risk patients with PMF diagnosed after 1990 (p=0.01). Conclusion: The current study provides mature survival data in PMF and PV using large cohorts of consecutive patients seen at a single institution. Although median survival is significantly better in PV compared to PMF, their survival curves converge after 20 years of follow-up, underscoring the poor long-term prognosis in PV patients. The study also suggests improved survival for high/intermediate-2 risk PMF in recent years. Disclosures: Off Label Use: hydroxyurea use in myelofibrosis.

Abstract Abstract 2909 Poster Board II-885 Background: Previous studies have identified sole abnormalities of del(20q) and del(13q) as prognostically favorable cytogenetic markers in primary myelofibrosis (PMF) (Tefferi et al. BJH 2001;113:763). A more recent study (Tam et al. Blood 2009;113:4171) confirmed these findings and suggested additional cytogenetic markers of prognosis. In the current study with larger numbers of informative patients studied at time of diagnosis, we wanted to validate these observations and examine the prognostic interaction between cytogenetic risk categorization and the International Prognostic Scoring System (IPSS). Methods: Patients with cytogenetic information at diagnosis were selected from the Mayo Clinic database of WHO-defined PMF. Specific cytogenetic categories were considered only in the presence of at least 5 informative patients; otherwise, they were included in the category of “other cytogenetic abnormalities”. Follow-up information was updated in July, 2009. Survival curves were prepared by the Kaplan-Meier method and compared by the log-rank test. Cox regression model was used for multivariable analysis. Results: 200 patients were studied (median age, 62 years; 63% males). The IPSS risk distributions were low in 66 patients, intermediate (int)-1 in 64, int-2 in 44 and high in 26. Cytogenetic findings at diagnosis were abnormal in 83 (42%) patients and included sole del(20q) in 21, complex (i.e. 3 or more abnormalities) in 13, sole del(13q) in 8, sole +8 in 7, sole +9 in 6, and other abnormalities in 28 patients. Median survivals in low, int-1, int-2 and high IPSS risk groups were 188, 71, 47 and 26 months, respectively (p < 0.0001). Median survival in patients with sole +9 was not reached and in those with sole del(13q), sole del(20q), normal karyotype, complex abnormalities and sole +8 was 112, 108, 80, 37 and 27 months, respectively, while it was 46 months for patients with other cytogenetic abnormalities (p = 0.01). Accordingly, sole abnormalities of +9, del(20q) and del(13q) were categorized as being favorable (n = 35) and complex abnormalities and sole +8 as unfavorable (n = 20); the respective median survivals were 112 and 34 months (p=0.002; Figure). Multivariable analysis confirmed the IPSS-independent prognostic value of cytogenetic risk categorization and the intra-IPSS risk prognostic distinction was most apparent in the int-1 group: median survival was 35 and 81 months in the presence of unfavorable or favorable cytogenetic markers, respectively (p=0.0009; Figure). Conclusion: The current study identifies sole +9, along with del(13q) and del(20q), as favorable and sole +8, along with complex abnormalities, as unfavorable cytogenetic markers of prognosis in PMF. Cytogenetic risk categorization in PMF has an IPSS-independent prognostic value that is important in patient selection for specific therapy. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 2895 Poster Board II-871 Background: Recent studies have reported a significant association between JAK2V617F acquisition and a specific JAK2 germline haplotype; rs12343867 (located at intron 14 of the JAK2 gene) is one of several SNPs that tag this haplotype. We performed rs12343867 SNP analysis in a consecutive cohort of patients with primary myelofibrosis (PMF) in order to study the clinical and laboratory correlates of the particular JAK2 haplotype and its effect on survival. Methods: Study patients were recruited form the Mayo Clinic database for PMF. Molecular studies were performed on DNA extracted from stored bone marrow. rs12343867 SNP genotyping was performed by a commercially available Taqman assay. Quantitative JAK2V617F analysis was done according to previously published methods. Standard statistical methods were used to test significance of associations between SNP genotype and other variables. Survival analysis was performed by the Kaplan-Meier method and comparisons made by the log-rank test. Cox regression model was used for multivariable analysis. Results: 132 patients with PMF were studied (median age 62, range 28-82; 82 males). Risk distribution according to the International Prognostic Scoring System (IPSS) for PMF were low in 39 (29%) patients, intermediate-1 in 41 (31%), intermediate-2 in 25 (20%) and high in 27 (20%). 77 (58%) patients were JAK2V617F positive; median mutant allele burden was 26% (range 1-85) and 21 patients displayed > 50% mutant allele burden. The rs12343867 genotype distributions were C/C 22%, C/T 44% and T/T 34% . The corresponding figures in JAK2V617F positive/negative cases were 31%/9%, 38%/53%, 31%/38% (p=0.01). Among the 21 patients with > 50% JAK2V617F allele burden, 14 (67%) displayed the C/C allele, 2 C/T and 5 T/T. The specific SNP genotype was not significantly affected by age (p=0.33), sex (p=0.46), leukocyte count (p=0.39), platelet count (p=0.09), or IPSS risk category (p=0.63). Patients were followed for a median of 54 months and during this period 73 (55%) deaths were documented. The T/T SNP genotype was significantly associated with shortened survival, compared to either C/C or C/T (p=0.001; Figure). Multivariable analysis showed this association to be independent of IPSS, JAK2V617F mutational status, age or sex. The adverse prognostic effect of the T/T genotype was also apparent when JAK2V617F negative (p=0.01) or positive (p=0.06) cases were analyzed separately. Conversely, JAK2 mutational status or allele burden did not affect survival in patients with T/T or C/C allele. Conclusion: The current study illustrates the non-random haplotype distribution of JAK2V617F in patients with PMF. More importantly, a non-JAK2 haplotype, tagged by the rs12343867 T allele, was associated with inferior survival that is not accounted for by IPSS or JAK2V617F mutational status. These findings, together with previous observations regarding shortened survival associated with low JAK2V617F allele burden, suggest the presence of molecular events in PMF that are more aggressive than JAK2V617F and not necessarily linked to the JAK2 haplotype. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 2906 Poster Board II-882 Background: The World Health Organization (WHO) classification system recognizes indolent SM (ISM) as an entity characterized by low systemic mast cell (MC) burden but frequent skin involvement. The WHO system also recognizes 2 provisional ISM sub-variants: smoldering SM (SSM) and bone marrow (BM) mastocytosis (BMM). The two are respectively characterized by increased systemic MC burden (presence of ≥ 2 ‘B-findings') and BM MC infiltration in the absence of skin or multiorgan visceral lesions. The prognostic relevance of this sub-classification remains unclear. Methods: The study population was drawn from a larger cohort of 342 adult SM patients (Blood. 2009 Jun 4;113(23):5727). Clinical data and BM histology were reviewed, and the diagnosis of ISM and its subclassification confirmed per the 2008 WHO proposal. The primary objectives of the study were to: (i) describe the clinical characteristics of a large cohort of ISM patients, within the context of the WHO classification; (ii) evaluate the prevalence of molecular and cytogenetic abnormalities; (iii) evaluate whether ISM subclassification is prognostically relevant on the basis of survival and risk of transformation to acute leukemia or aggressive SM (ASM). Results: (i) Clinical characteristics: 159 ISM patients were evaluated (69 males; median age 49 years, range 19-84); 22 (14%) had SSM, 36 (23%) BMM, and 101 (63%) ‘ISM-other' (ISMo). By definition, ‘B-findings' were absent in BMM patients. ‘B-findings' in SSM (and ISMo) patients was as follows: hepatosplenomegaly and/or lymphadenopathy 91% (21%), BM MC >30% or serum tryptase level >200ng/mL 68% (8%), and hypercellular BM or dysmyelopoiesis without cytopenias 50% (2%). SSM patients were older (p<0.01) and more frequently displayed constitutional symptoms (p<0.01), and anemia (p<0.01). MC mediator-release symptoms (p=0.01), including anaphylaxis (p<0.01), were more frequent in BMM. The following MC-mediators were studied: serum tryptase (57%), beta prostaglandin F2alpha (45%), urine methylhistamine (32%), and urine histamine (21%) – significant differences were noted amongst the ISM subgroups with the following relationship: SSM>ISMo>BMM (p<0.01). (ii) Molecular and cytogenetic abnormalities: Complete karyotype information was available for 55 patients; only 1 patient (with ISMo) had an abnormal karyotype. Fifty nine patients were screened for KITD816V and JAK2V617F; JAK2V617F was universally absent, and distribution of KITD816V was not significantly different amongst the ISM subgroups: SSM (100%), BMM (92%), and ISMo (69%). (iii) Survival and risk of disease transformation: At a median follow of 27 months (range <1-417), 26 deaths were recorded (ISMo 14, SSM 10, and BMM 2), and the combined median survival was 198 months: ISMo 301 months, SSM 120 months, and BMM (not reached) (p<0.01; Figure). Transformation to acute leukemia and ASM was seen in 1 patient (SSM) and 3 patients (2 SSM and 1 ISMo), respectively. Conclusions: Among WHO-defined ISM patients, SSM is associated with significantly shorter survival whereas BMM and ISMo are prognostically similar. If these observations are confirmed by others, consideration may be given to classifying SSM as a distinct subcategory of SM, instead of a sub-variant of ISM as it currently stands. Disclosures: No relevant conflicts of interest to declare.