Gangat, Naseema

Abstract BACKGROUND. In primary myelofibrosis (PMF), survival from time of diagnosis is predicted by the international prognostic scoring system (IPSS), and from time of referral, by the dynamic IPSS (DIPSS) or DIPSS-plus. JAK2/CALR/MPL mutational status and presence and number of other prognostically-relevant mutations (ASXL1, SRSF2, EZH2, IDH1/2) provide IPSS/DIPSS-plus independent prognostic information. The objective in the current study was to revise IPSS, by including mutation-relevant prognostic information. METHODS. The study included 986 PMF patients divided into learning (n=588) and validation (n=398) cohorts. Previously published methods were used to screen for mutations involving JAK2,MPL, CALR, EZH2, ASXL1, IDH1/2 and SRSF2. The clinical variables assessed were those previously identified as being prognostically-relevant by IPSS or DIPSS-plus. The prognostic model (MIPSS) was developed through a stepwise selection process, based on a z-test of the regression coefficients, and its relative quality was measured by means of the Akaike information criterion. RESULTS. In the Italian learning cohort (n=588),median follow-up was 3.6years (95% CI, 0.03-30.8) for alive patients and 196 (33.3%) deaths and 67 leukemic transformations were documented. IPSS risk distribution was low in 26%, intermediate-1 in 30%, intermediate-2 in 24% and high in 20%. Mutational frequencies were approximately 63% for JAK2, 20% CALR, 6% MPL, 7% EZH2, 22% ASXL1, 2.5% IDH1/2 and 9% SRSF2. Constitutional symptoms were recorded in 28.6% of patients, splenomegaly 75% (18% >10cm from LCM) and grade 3 fibrosis 21%. Overall 252 patients were evaluable for karyotype and abnormalities were detected in 35%, including 9.5% unfavorable. Univariate analysis identified the following risk factors for inferior survival: age >60 years, constitutional symptoms, hemoglobin <100g/L, leukocytes >25x109/L, platelets <200x109/L, circulating blasts 1% or greater, splenomegaly >10cm, grade 3 fibrosis, unfavorable karyotype, triple-negativity for JAK2, MPL and CALR (TN), JAK2 or MPL mutation, and mutations in ASXL1, SRSF2, EZH2 or IDH1/2. In multivariable analysis, age >60 years, constitutional symptoms, hemoglobin <100g/L, platelets <200x109/L, TN, JAK2 or MPL mutation, ASXL1 and SRSF2 mutation remained significant; these variables were subsequently assigned the following HR-weighted adverse points: 1.5, 0.5, 0.5, 1.0, 1.5, 0.5, 0.5 and 0.5, respectively. Subsequently, four risk groups with no overlap in the 95% CI of their survival curves were delineated (Figure 1A): low (score 0-0.5); Intermediate-1 (score 1-1.5); Intermediate-2 (score 2-3.5); and high (score 4 or greater). The number of patients in each risk category, median survivals and HR and 95% CI values are included in figure 1A. Akaike information criterion indicated that MIPSS performed better than IPSS in predicting survival (1611.6 vs 1649.0). Leukemia-free survival was also predicted by high (p<0.01) and intermediate 1/2 (p<0.01) risk MIPSS. In the Mayo Clinic validation cohort (n=398), median age 63 years; males 64%,median follow-up for alive patients was 7.5 years and 271 (68%) deaths and 51 (13%) leukemic transformations were documented. DIPSS-plus risk distribution was low in 13%, intermediate-1 18%, intermediate-2 37% and high 32%. Mutational frequencies were approximately 51% for JAK2, 30% CALR, 7.5% MPL, 5% EZH2, 36% ASXL1, 5.6% IDH1/2 and 13% SRSF2. MIPSS performed equally well in this cohort, as illustrated in figure 1B, which includes number of patients in each risk category with their median survival and HR and 95% CI values. Leukemia-free survival in the Mayo cohort was also predicted by high (p<0.01) and intermediate-2 (p=0.04) risk MIPSS. Patients in the Mayo cohort were fully annotated for karyotype, which was MIPSS-independent in its prognostic value for both overall (p<0.01) and leukemia-free (p<0.01) survival. CONCLUSIONS. MIPSS addresses the mutation-relevant prognostic information gap in IPSS and performs equally well in the setting of patients seen at time of diagnosis or referral. Karyotype carries MIPSS-independent prognostic value that is recognized in an alternative GIPSS prognostic model (see accompanying ASH 2014 abstract), which complements MIPSS. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Abstract Background: Relapse after ATRA-based induction therapy is relatively uncommon in patients with acute promyelocytic leukemia (APL). Long term follow up studies have estimated a 15-25% relapse rate. Autologous and allogeneic hematopoietic stem cell transplantation (HCT) has been used as an effective salvage strategy. We present a single institution study of the outcomes of patients with relapsed APL that underwent HCT. Methods: After due IRB approval, the Mayo Clinic Transplant Database was retrospectively reviewed to identify all patients across three Mayo Clinic sites with relapsed APL that underwent HCT from 1995-2013. Data was abstracted at diagnosis and at relapse. The aims of this study were to report the descriptive characteristics of patients, with a focus on HCT outcomes. Results: Baseline Patient Characteristics A total of 15 patients (9 (60%) males) with relapsed APL that underwent HCT were identified. Median age was 36 years (range: 19-63) and median follow up from diagnosis was 8.8 years (range: 1.7-17). 2 (13%) deaths (1 from relapse) were recorded. 14 (93%) received ATRA and anthracycline-based induction therapy and 1 received anthracycline-based induction without ATRA. All relapsed patients achieved a complete remission (CR) after induction. Median time to relapse was 1.6 years (range: 0.6-3.9). 10 (67%) patients had a medullary relapse (hematologic-7(70%), cytogenetic -2 (20%) and molecular-1(10%)), 3 (20%) had additional extramedullary (EM) disease (CNS-2, myeloid sarcoma-1), while 2 (13%) presented with EM disease only (CNS-2). Salvage regimens included ATRA in 5 (33%) patients and arsenic trioxide (ATO) in 8 (53%) patients. 12 (80%) patients were transplanted in CR2 and 1 in CR3 (7%), while 2 (13%) had persistent disease (PD) at time of HCT. Allogeneic HCT 4 (27%) patients with a median age of 37 years (range: 33-49) underwent allogeneic HCT. 2 (50%) patients received myeloablative (MA) conditioning and 2 received reduced-intensity conditioning (RIC). 2 patients who underwent MA HCT had PD at time of transplant, while 1 patient in CR3 received a RIC. 2 (50%) patients developed acute GVHD while 2 (50%) had extensive stage chronic GVHD. At a median follow up of 2.6 years (range: 0.3-10.9), 3 (75%) patients remain alive and disease-free. 1 patient died of infectious complications within 100 days of transplant. Autologous Transplantation 11 (73%) patients with a median age of 40 years (range: 23-68) underwent autologous HCT with MA conditioning. 7 (64%) patients were in molecular remission at time of HCT, 3 (27%) patients transplanted before 2004 were in cytogenetic remission and information about type of remission was unavailable in 1 patient. At a median follow up of 6.8 years (range: 0.5-16) since HCT, 1 (9%) patient had a documented relapse at 175 days after HCT and died of disease-related complications. 10 (91%) are alive and in remission. Conclusions: Our single-institution study reaffirms the efficacy of HCT for APL patients with medullary and EM relapse. Autologous HCT has excellent long-term results in selected patients in CR2. Allogeneic HCT was mainly reserved for patients with high risk disease (CR3) and persistent disease at time of HCT. Table 1: Baseline Patient Characteristics N (%) Number of patients 15 Follow up (years) (median, range) 8.8 (1.7-17) Age at diagnosis (years) (median, range) 36 (19-53) Gender Male 9 (60%) Female 6 (40%) Sanz risk score High 4 (29%) Intermediate 8 (57%) Low 2 (14%) Induction Regimen ATRA + anthracycline 14 (93%) Anthracycline-based 1 (7%) Response to induction therapy CR 15 (100%) Time from diagnosis to relapse (years) (median, range) 1.6 (0.6 - 3.9) Type of relapse Hematologic 7 (47%) Cytogenetic 2 (13%) Molecular 1 (7%) Hematologic and EM 3 (20%) CNS only 2 (13%) Salvage regimen ATRA-based 5 (33%) ATO-based 8 (53%) Chemotherapy only 2 (13%) Table 2: Outcomes at HCT N (%) Age at HCT (years) (median, range) 38 (23-68) Disease status at HCT CR2 12 (80%) CR3 1 (7%) PD 2 (13%) Type of HCT Allogeneic 4 (27%) Autologous 11 (73%) Conditioning regimen Myeloablative 13 (87%) Non-myeloablative 2 (13%) Follow up since HCT (years) (median, range) 4.5 (0.3 - 16.3) Disease status at last follow up CR 13 (86%) Relapsed disease 1 (7%) Unable to assess 1 (7%) Alive at last follow up 13 (87%) Disclosures No relevant conflicts of interest to declare.

Abstract Abstract 1746 Diagnosis of essential thrombocythemia (ET) has been updated in the last World Health Organization (WHO) classification, that provides a guideline to distinguish ET from early/prefibrotic primary myelofibrosis. These two conditions differ in term of disease evolution and survival (Barbui et al, J. Clin. Oncol. 2011). To design a prognostic model for survival in WHO-defined ET (International Prognostic Score for Essential Thrombocythemia, IPSET), we studied 891 patients with strict WHO diagnostic criteria. Demographics have been presented elsewhere (Barbui et al, J. Clin. Oncol. 2011). We tested the prognostic impact on survival of age, prior thrombosis, leukocyte count, platelet count, hemoglobin level, JAK mutational status, splenomegaly. Harrell's C concordance statistics were used to set the best cutoff levels of continuous variables in order to predict survival. Univariate Cox proportional hazard regression showed that age over 60 years (P<.0001), leukocyte count greater than 11 x109/L (P<.0001), anemia (P=.04), platelet count greater than 1000 x109/L (P<.004) and prior history of thrombosis (P< 0001) were significant risk factors for survival. Age over 60 years (hazard ratio-HR- 6.5, 95% CI: 3.9–10.7; P<.0001), leukocyte count greater than 11 × 109/L (HR: 3.1, 95% CI: 2–4.7; P<.0001) and prior history of thrombosis (HR: 2.9, 95% CI: 1.9–4.5; P< 0001) retained statistical significance on survival by multivariable analysis and were included in the new prognostic model. We assigned each factor an integer weight close to the corresponding HR in the multivariable Cox regression: weight 2 for age over 60 years; weight 1 for leukocyte count greater than 11 x109/L and for prior thrombosis. Finally, we defined the IPSET score by allocating patients into three risk categories with significantly different survival according to the sum of weights: low risk (sum of weights=0; n= 342; median survival not reached), intermediate risk (sum=1-2; N=374; median survival 24.5 years), and high risk (sum=3-4, n=158; median survival 13.8 years). Fisher exact test did not reveal a difference in the distribution of the causes of death among IPSET categories. We validated the model in two independent cohorts: one from Germany (132 WHO-defined ET) and another from France (234 ET patients not strictly diagnosed according to WHO). Log rank test and Cox regression showed significant differences in term of survival among IPSET categories in both series. Finally, we designed an age-specific IPSET model for patients younger than 60 years (IPSET-y). Using the same methodology, we found that age over 45 years (weight 2), leukocyte count greater than 11 × 109/L (weight 1) and prior history of thrombosis (weight 1) were independent risk factors for survival. IPSET-y defined three risk categories (LR, sum=0; IR, sum=1-2; HR, sum=3–4) with a median survival not reached in LR and IR, and of 22.3 years in HR. In conclusion, IPSET, based on age over 60 years, leukocyte count greater than 11 x109/L and history of thrombosis allows prognostic assessment of WHO-defined ET. The validation process makes IPSET applicable in all patients phenotypically appearing as ET. IPSET models may be useful for treatment decision-making. Disclosures: Vannucchi: Italfarmaco: Consultancy; Novartis: Honoraria. Gisslinger:AOP Orphan Pharmaceuticals AG: Research Funding.

Abstract Abstract 3846 INTRODUCTION There is strong evidence indicating that the clear-cut separation of prefibrotic primary myelofibrosis (PMF) from essential thrombocythemia (ET) by consequent application of the World Health Organization (WHO) 2008 criteria is reflected in different, well defined clinical pictures and divergent prognoses (Barbui et al, JCO 2011,Thiele et al, Blood 2011). Very recently the specific risk profile for arterial and venous thrombosis in WHO- diagnosed ET was published (Carobbio et al, Blood 2011). In PMF so far all published data on vascular events were exclusively based on overt disease manifestations until now there are no data available regarding prefibrotic stages. Consequently, we aimed to evaluate the corresponding risk profile of patients with WHO-diagnosed prefibrotic PMF. METHODS A total number of 264 patients with WHO-defined prefibrotic PMF derived from either the Medical University of Vienna or an International Database (Barbui et al, JCO 2011) were studied. Nonfatal thrombotic events considered in this study were reported as rates per 100 patient-years and included transient ischemic attacks, thrombotic cerebrovascular accidents, coronary artery disease, myocardial infarction, peripheral arterial disease, deep vein thrombosis of peripheral vasculature, pulmonary embolism, and abdominal large vein thrombosis. Cardiovascular risks factors considered, comprised of arterial hypertension, diabetes mellitus and tobacco use. To evaluate risk factors for total thrombosis and for arterial and venous events in particular multivariate Cox- regression analysis including the co-variables sex, age, previous thrombotic event, laboratory parameters measured at diagnosis and need for cytoreductive and/or antiplatelet therapy during follow-up was calculated. P values less than 0.05 were considered as statistically significant. RESULTS After a median follow- up of 5.8 years (range0.0 – 27.2), the total rate of non fatal thrombotic events was 2.1% patient-years (95% CI, 1.5–2.8); the incidence of arterial events was higher (1.7% patient- years) than of venous events (0.6% patient-years).Considering thrombosis in general a higher white blood cell (WBC) count enhances the risk significantly (p=0.005; HR 1.15). This is also true in arterial events in particular (p=0.047; HR 1.12). A lower platelet count is associated with a higher risk for thrombotic events; for thrombosis in general this association is of borderline significance (p=0.056; HR 0.99), for arterial thrombosis in particular of significance (p= 0.042; HR 0.99). A lower hemoglobin level is associated with a higher risk for venous thrombosis (p=0.007; HR 0.59). CONCLUSION Leukocytosis appears as a risk factor for thrombosis in general and also for arterial thrombosis in particular in WHO-diagnosed prefibrotic PMF. Moreover, higher platelet counts seem to decrease significantly the risk for thrombotic events in general and arterial thrombosis in particular. Anemia is associated with a higher risk for venous thrombosis. These observations are partly in line with recently published findings in WHO-diagnosed ET (Carobbio et al,2011) and might indicate the existence of a specific risk profile for thrombotic events in prefibrotic PMF. This is the first study reporting data on the risk profile for thrombosis in WHO-diagnosed prefibrotic PMF. Certainly these findings ask for validation in a larger patient population. Disclosures: Gisslinger: Novartis: Speakers Bureau; Celgene Austria: Research Funding, Speakers Bureau; AOP-Orphan Pharmaceuticals AG: Speakers Bureau. Vannucchi:Novartis: Honoraria.

Abstract Background : Recent studies have suggested significant associations between karyotype and certain molecular or phenotypic features in primary myelofibrosis (PMF). In the current study of 835 consecutive patients, we examined the spectrum and prevalence of cytogenetic abnormalities in PMF and their molecular and phenotypic correlates. Methods : PMF diagnosis was according to World Health Organization criteria. Cytogenetic analysis and reporting was done according to the International System for Human Cytogenetic Nomenclature. Statistical analyses considered clinical and laboratory parameters obtained at time of cytogenetic studies. Spectrum and frequency of cytogenetic abnormalities : Analyzable metaphases were obtained in 826 (99%) of 835 patients studied; 681(82%) had ≥20 metaphases analyzed. 352 (42.6%) patients had abnormal karyotype, including 240 (68.2%) sole, 64 (18.2%) two and 48 (13.6%) complex; comparison of these groups revealed lower platelet count (p<0.01), higher DIPSS-plus score (p=0.03) and higher percentage of younger patients (p=0.04) with complex abnormalities. Monosomal karyotype was noted in 20 (5.7%) patients. Approximately 150 individual abnormalities were identified; most frequent were 20q- (23.3%), 13q- (18.2%), +8 (11.1%), +9 (9.9%), duplication of chromosome 1q (9.7%) and -7/7q- (7.1%). Other notable abnormalities including i(17q) (1.4%), 12p- (1.1%) and inv(3) (0.6%) were much less frequent. Trisomy 8 was the most frequent in the context of complex abnormality (25%). Among the 500 patients seen within one year of initial diagnosis, 179 (35.8%) had abnormal karyotype, which included 121 (67.6%) sole, 31 (17.3%) two and 27 (15.1%) complex abnormalities; the most common abnormalities were 20q- (24.6%), 13q- (15.1%), +8 (14%) and +9 (10%) whereas 11q- (1.7%), i(17q) (1.1%), inv(3) (0.6%), and 12p- (0.6%) were infrequent. Molecular correlates : 476 patients were annotated for JAK2, CALR and MPL mutations; abnormal karyotype frequencies were 43% in JAK2, 42% CALR, 33% MPL mutated and 34% triple-negative cases (p=0.3). 13q- was associated with mutant CALR (p=0.03) and +9 with mutant JAK2 (p=0.02). Subsets of patients were also screened for ASXL1, EZH2, IDH, SRSF2, U2AF1, and SF3B1 mutations; in all instances, mutational frequencies were higher in patients with normal karyotype, reaching significance with ASXL1 (p=0.02) and U2AF1 (p=0.01). Mutant SRSF2 was associated with 20q- (p=0.02). Phenotypic correlates : Phenotypic correlates included abnormal karyotype with anemia (p=0.02), leukopenia (p<0.01) and thrombocytopenia (p<0.01); complex karyotype with younger age (p=0.04) and thrombocytopenia (p<0.01); leukopenia with 20q-, +8 and -7/7q-; and thrombocytopenia with 20q- and -7/7q-. Cytopenias were less likely to occur with 13q- (p<0.01), which was instead associated with thrombocytosis (p<0.01). 20q- was associated with lower incidence of marked leukocytosis (p=0.02). Trisomy 8 was associated with lower incidences of constitutional symptoms (p<0.01) and marked splenomegaly (p<0.01). Conclusions : The association of 13q- with CALR mutations in PMF might underlie its association with both thrombocytosis and favorable prognosis. The association of +9 with JAK2 mutations might reflect selective clonal advantage through JAK2V617F dosage enhancement or mutation-induced chromosomal instability. The association of 20q- with mutant SRSF2 and thrombocytopenia warrant further clarification of its reported association with favorable prognosis. Disclosures No relevant conflicts of interest to declare.

Abstract Abstract 3833 Background: Survival in primary myelofibrosis (PMF) is assessed by the Dynamic International Prognostic Scoring System (DIPSS) (Blood 2010;115:1703) and DIPSS-plus (JCO 2011;29:392). The latter is based on eight risk factors including age>65 years, constitutional symptoms, hemoglobin <10 g/dL, red blood cell transfusion need, leukocyte count >25 × 109/L, platelet count <100 × 109/L, peripheral blood (PB) blasts ≥1% and unfavorable karyotype. Recent studies have highlighted the prognostic significance of monosomal karyotype (MK) (Blood 2011;117:5612), unfavorable karyotype (Leukemia 2011;25:82) and platelet count <100 × 109/L ((JCO 2011;29:392), for leukemic transformation (LT) in PMF. Methods: A combination of multivariable and receiver operating characteristic (ROC) analyses were applied to a Mayo Clinic database of 884 karyotypically-annotated patients with PMF, in order to define karyotype-dependent and karyotype-independent risk models for LT. The karyotype-independent model was further validated in a separate cohort of 525 PMF patients from an international database (Blood 2010;115:1703). Patients in the Mayo cohort were evaluated at time of referral and those of the international database at time of initial diagnosis. Results I: Sixty cases of LT were documented. Karyotype (categorized into MK, inv(3)/i(17q) abnormalities, other unfavorable, and favorable), PB blast percentage (as a continuous variable), and platelet count (as a continuous variable) were the most reliable (p<0.01) in predicting leukemia-free survival (LFS). The best discriminant levels for inferior LFS were MK (HR 6.2, 95% CI 2.2–17.1), inv(3)/i(17q) abnormalities (HR 7.6, 95% CI 1.8–33.3), PB blast ≥2% (HR 2.4, 95% CI 1.4–4.2) and platelet count ≤41 × 109/L (HR 2.6, 95% CI 1.3–5.1). MK and inv(3)/i(17q) abnormalities were subsequently consolidated into one “very high risk” cytogenetic category (n =27), with a corresponding HR of 6.6 (95% CI 2.7–16.0). HR-based risk scores were assigned to “very high risk” karyotype (2 points), PB blast ≥2% (one point) and platelet count ≤50 × 109/L (one point) to classify patients into low (no adverse points; n =522), intermediate (one adverse point; n =290) and high risk (two or more adverse points; n =72) groups; the corresponding 3-year LT rates were 3%, 10% (HR 2.6; 95% CI 1.4–4.6) and 35% (HR 9.4, 95% CI 4.7–18.7) (Figure 1). Results II: The karyotype-independent model was based on PB blast percentage and platelet count only; low-risk (no adverse points; n =525), intermediate-risk (one adverse point; n =311) and high-risk (two adverse points; n =48); the corresponding 3-year LT rates were 3%, 12% (HR 3.1, 95% CI 1.8–5.4; p<0.0001) and 25% (HR 6.0, 95% CI 2.6–14.1). The karyotype-independent model was validated in a separate cohort of 525 PMF patients with 70 documented cases of LT, from an international database (Blood 2010;115:1703). Conclusions: The current leukemia risk models are applicable at diagnosis or during follow-up, in the presence or absence of cytogenetic information, and complement DIPSS-plus in the comprehensive prognostication of patients with PMF. Disclosures: Vannucchi: Novartis: Honoraria.

Abstract Background: KIT D816V is considered the driver mutation in systemic mastocytosis (SM) however this mutation alone does not explain the diverse clinical manifestations of SM. While mutations in other myeloid-relevant genes have been reported in SM, their pattern(s) of co-segregation and prognostic value, independent of age and SM subtype, have not been fully defined in a mature dataset. Objectives: In this pilot study of advanced SM patients, we sequenced a panel of myeloid-relevant genes for known pathogenic mutations, to ascertain: (i) the frequency of individual mutations; (ii) the pattern(s) of mutation co-segregation; and (iii) the prognostic value of mutations, both individually and in combination, on overall- (OS) and leukemia-free survival (LFS). Methods: The current study was approved by the Mayo Clinic institutional review board. SM was classified as per World Health Organization criteria. DNA was isolated from archived bone marrow (BM) cell pellets. Next-generation deep sequencing by HiSeq SBS chemistry (Illumina) was performed to investigate the coding regions of 22 genes: KIT, JAK2, CALR, SRSF2, U2AF1, SF3B1, ASXL1, TET2, EZH2, SETBP1, DNMT3A, IDH-1/2, SUZ12, CBL, NRAS, FLT3, PTPN11, RUNX1, CEBPA, TP53 and NPM1. Results: We studied 19 patients with advanced SM; 6 had aggressive SM (ASM) and 13 had SM with an associated hematological disease (SM-AHD). Of the latter, 5 patients (38%) had myeloproliferative neoplasm-unclassified (MPN-u), 3 (23%) chronic myelomonocytic leukemia (CMML), 2 (15%) acute myeloid leukemia (AML), and 1 (8%) each polycythemia vera, myelodysplastic syndrome, and multiple myeloma. The median follow up from diagnosis was 20 months (range 2 to 84). Over this period, 5 patients (26%) developed leukemic transformation and 12 patients (63%) have died. KIT D816V was identified in 9 (47%) patients; 9 of 10 patients who tested negative by deep sequencing were screened by allele-specific PCR (sensitivity ~0.01%), with 8 additional patients testing positive. Thus, overall KIT D816V frequency was 89%. Fourteen (74%) patients harbored at least one additional non-KIT mutation; of these 7 patients had one additional mutation (ASXL1/TET2/SF3B1 = 2 each and JAK2 =1), 3 patients each had two and three additional mutations, and 1 patient had 4 additional mutations. The most frequently mutated genes (other than KIT) were ASXL1/TET2 (5 patients each, 26%), CBL (4 patients, 21%), SETBP1/SF3B1/DNMT3A (2 patients each, 11%) and JAK2/CALR/FLT3/IDH-1/RUNX1/TP53 (1 patient each, 5%). There was no overlap between patients harboring TET2 and ASXL1 mutations however 2 and 1 CBL-mutated patients concurrently harbored TET2 and ASXL1 mutations, respectively. SETBP1 and SF3B1 but not DNMT3A mutations occurred independently of TET2 and ASXL1 mutations. The distribution of mutations was similar between ASM and SM-AHD subgroups. When considered individually, the following non-KIT mutated genes (present in at least 2 patients) were associated with significantly inferior OS: ASXL1, CBL and SETBP1 (p<0.05). When the 3 mutated genes were considered together, only ASXL1 and CBL maintained their significance, independent of age and SM subtype, for inferior OS (Hazard ratio (95% confidence interval)=34.8 (3.1-393.9) and 59.7 (4.1-861.5), respectively). Patients harboring ASXL1 and/or CBL mutations (n=8, 8 deaths, median OS=11 months) had a significantly worse OS as compared to those without either mutation (n=11, 4 deaths, median OS=84 months) (p=0.0002) (Fig 1). When considering the number of non-KIT mutations (zero, one, two, three and four mutations in 5, 7, 3, 3 and 1 patients, respectively), the group with ≥3 mutations (n=4, 4 deaths, median OS=7 months) had a significantly inferior OS as compared to those with <3 mutations (n=15, 8 deaths, median OS=48 months) (p=0.01) (Fig 2). Presence of mutations was not correlated with LFS in this analysis. Conclusions: In this cohort of advanced SM patients, non-KIT mutations were frequent (prevalence 74%). TET2, ASXL1, SETBP1 and SF3B1, but not CBL or DNMT3A, mutations were mutually exclusive. Presence of ASXL1 and CBL mutations was associated with significantly inferior OS (HR=35 and 60, respectively), independent of known prognostic factors. An increasing number of non-KIT mutations (≥3, HR=5.9) was also associated with a significantly worse survival outcome. Sequencing results from a larger cohort will be presented at the meeting. Figure 1. Figure 1. Figure 2. Figure 2. Disclosures Pardanani: Stemline: Research Funding.

Abstract Background : TET2, located on chromosome 4q24, is frequently mutated in the majority of patients with chronic myelomonocytic leukemia (CMML). TET2 has 11 exons, and variations, especially in exon 3 have been described as a part of age related clonal hematopoiesis (Jaiswal NEJM 2015). In CMML, somatic TET2 mutations in the absence of ASXL1 mutations (ASXL1wt/TET2mt) were previously shown to impart a favorable outcome on survival (Patnaik BCJ 2015). In the current larger CMML patient cohort, we describe the number and type of TET2 mutations and examine their phenotypic and prognostic effects. Methods : 261 patients with CMML were included in the study. All patients had bone marrow (BM) biopsies and cytogenetics performed at diagnosis. Targeted capture assays were carried out on BM DNA specimens obtained at diagnosis for the following genes; TET2, DNMT3A, IDH1, IDH2, ASXL1, EZH2, SUZ12, SRSF2, SF3B1, ZRSR2, U2AF1, PTPN11, Tp53, SH2B3, RUNX1, CBL, NRAS, KRAS, JAK2, CSF3R, FLT3, KIT, CALR, MPL, NPM1, CEBPA, IKZF, and SETBP1. TET2 (NM_001127208.2) coverage extended from exons 3-11, with frame shift, non-sense, and missense variations considered pathogenic. Previously annotated single nucleotide polymorphisms (http//www.hapmap.org) were considered non-pathogenic. Results: Among the 261 study patients, 65% were males and median age was 70 years (range, 28-91). 154 (59%), 64 (25%) and 43 (16%) patients were classified as CMML-0, 1 and 2, respectively. At a median follow-up of 23 months, 174 (67%) deaths and 37 (14%) leukemic transformations were documented. Mutational frequencies ≥4% were encountered in; ASXL1 45%, TET2 42%, SRSF2 40%, NRAS 14%, SETBP1 13%, CBL 10%, JAK2 7%, RUNX1 6%, DNMT3A 6%, U2AF1 6%, SF3B1 5%, ZRSR2 4%, Tp53 4% and IDH2 4%. i) TET2 mutations type, number and phenotypic correlates: TET2 mutations were seen in 109 (42%) patients; these included frameshift 33 (30%), nonsense 29 (27%) and missense 11 (10%) variants whereas 36 (33%) had more than one type of mutation. Overall, 57 (52%) patients had more than 1 TET2 mutations: 52 (48%) patients had 1, 46 (42%) 2 and 11 (10%) ≥3 TET2 mutations. Among all 109 TET2 mutated patients, 65% were male, and median age was 71 years with no significant difference in age and gender distribution between mutated and un-mutated cases, or type of TET2 mutations; however, older patients were more likely to carry multiple TET2 mutations (p=0.01). Compared to their un-mutated counterparts, TET2 mutated cases were less likely to have a low hemoglobin (p<0.001), circulating immature myeloid cells (IMC) (p=0.001), peripheral blood (PB) (p=0.009) and BM blasts (p=0.009), and have high-risk stratification per Mayo Molecular Model (p<0.001); these differences were not affected by the type or number of TET2 mutations. TET2 mutated cases were more likely to have a higher frequency of SRSF2 (p=0.004) and lower frequency of ASXL1 (p=0.03), Tp53 (p=0.04) and IDH1/2 mutations (p<0.001); these associations were also not affected by the type or number of TET2 mutations. ii) Impact on survival: Median survival for the entire cohort (n=261) was 24 months. In univariate analysis, survival was superior in TET2 mutated (median 33 months) versus wild-type (median 21 months) patients [p=0.03; HR 1.3 95% CI 1.12-1.86] (figure 1A). This survival difference remained significant after adjustment for age (p=0.04), leukocyte count (p=0.017), absolute monocyte count (p=0.02), absolute lymphocyte count (p=0.02), platelet count (p=0.015), circulating IMC (p=0.03), DNMT3A (p=0.02) and ASXL1 (p=0.045) mutations; however, significance was lost after adjustment for abnormal karyotype (p=0.32) and the Mayo Molecular Model (p=0.0003). These observations were not affected by the type or number of TET2 mutations. Finally, our previous observation regarding the survival advantage of ASXL1wt/TET2mt versus other genotypes was most apparent for patients with multiple TET2 mutations (p=0.02) (figure 1B). Conclusions: TET2 mutations are common in CMML and constitute approximately equal proportions of frameshift and non-sense mutations, while missense mutations are less frequent. Majority of TET2 mutated CMML cases harbor more than one mutant variant. Regardless, the relevance of type and number of TET2 mutations in CMML was limited to an association between older age and number of mutations and the latter with possibly improved survival in the absence of clonal ASXL1 mutations. Disclosures No relevant conflicts of interest to declare.

Abstract Background The Dynamic International Prognostic Scoring System (DIPSS)-plus currently provides the most comprehensive prognostic model for primary myelofibrosis (PMF) (JCO 2011;29:392). DIPSS-pluse uses eight independent predictors of inferior survival: age >65 years, hemoglobin <10 g/dL, leukocyte count >25 x 109/L, circulating blasts ³1%, constitutional symptoms, unfavorable karyotype, red cell transfusion need and platelet count <100 x 109/L. More recently, type 1/type 1-like CALR driver mutational status and ASXL1 andSRSF2 mutations were identified as additional DIPSS-plus-independent risk factors for survival in PMF (JAMAOncol. 2015;1:97). Based on our earlier preliminary observation (Leuk Res. 2007;31:1503), we conducted the current study to fully examine the additional prognostic relevance of monocytosis (absolute monocyte count ≥1 x 10(9)/L) in PMF. Methods Study patients fulfilled the 2016 WHO criteria for the diagnosis of PMF, including both pre-PMF and overt PMF (Blood. 2016;127:2391). Additional selection criteria included the availability of absolute monocyte count (AMC) and percentage at time of referral. Targeted next generation sequencing was used to screen for prognostically-relevant mutations (Blood 2015 126:354). Statistical analyses considered clinical and laboratory parameters obtained at time of initial referral to the Mayo Clinic. Results Patient characteristics: The study population included 454 patients (median age 64 years; 62% males); 293 (64%) patients harbored JAK2 mutations, 74 (16%) type 1/like CALR, 16 (3%) type 2/like CALR, 24 (5%) MPL and 47 (10%) were "triple-negative". DIPSS-plus risk distribution was 29% high, 38% intermediate-2, 17% intermediate-1 and 15% low; 27% displayed red cell transfusion-dependency, 29% constitutional symptoms, 70% palpable splenomegaly and 36% abnormal karyotype, including 13% with unfavorable karyotype. 301 patients were screened for ASXL1 mutations with 39% mutated, 297 for SRSF2 mutations with 15% mutated, 286 for U2AF1 with 18% mutated, 253 for SF3B1 with 6% mutated, 229 for EZH2 with 5% mutated and 110 for IDH1/2 with 7% mutated. Clinical, cytogenetic and molecular comparisons between PMF patients with and without monocytosis: Among all study patients, 376 (83%) displayed AMC <1 x 10(9)/L; the remaining had either moderate (AMC between 1 and 3 x 10(9)/L; n=65) or marked (AMC >3 x 10(9)/L; n=13) monocytosis. Comparison of these three groups revealed that monocytosis was significantly associated with older age (p=0.0001), higher leukocyte count (p<0.0001), lower platelet count (p=0.01), higher circulating blast percentage (p=0.0002) and higher DIPSS-plus risk distribution (p=0.01). There were no significant differences in the distribution of driver mutations, ASXL1, SRSF2, U2AF, SF3B1, EZH2 or IDH1/2 mutations or incidence of unfavorable karyotype. Survival analysis: After a median follow up of 3.2 years, 265 (58%) deaths and 38 (8%) leukemic transformations were documented. In univariate analysis, all 8 variables included in DIPSS-plus were significantly associated with shortened survival (p<0.001 in all instances). Significant risk factors in univariate analysis also included AMC >3 x 10(9)/L (p<0.0001; HR 5.6, 95% CI 3.1-10.0), AMC 1 to 3 x 10(9)/L (p<0.0001; HR 2.1, 95% CI 1.5-2.9), absence of CALR type 1/type 1-like (p<0.0001) and presence of ASXL1 (p<0.0001) or SRSF2 (p<0.0001) mutations. The significant difference in survival between the three AMC categories (i.e. <1, 1-3 and >3 x 10(9)L) was independent of each one of the eight DIPSS-plus variables, DIPSS-plus, driver mutational status, ASXL1 and SRSF2 mutations (p<0.0001 in all instances). The survival difference between patients with and without monocytosis was evident in both high/intermediate-2 and low/intermediate-1 DIPSS-plus risk groups (Figure). Patients with monocytosis were also more likely to undergo leukemic transformation (HR 3.0, 95% CI 1.4-6.5) and this effect was also independent of karyotype, driver mutational status, ASXL1 or SRSF2 mutations. Conclusion The current study identifies monocytosis as a powerful risk factor for both overall and leukemia-free survival in PMF and the effect was independent of currently established prognostic models and genetic risk factors. It was particularly noteworthy to document similar distribution of driver mutations among the three monocyte categories. Figure Figure. Disclosures No relevant conflicts of interest to declare.

Abstract Background Polycythemia Vera (PV) constitutes one of the three BCR-ABL1-negative myeloproliferative neoplasms and is characterized by clonal erythrocytosis and the almost invariable presence of JAK2 mutation. An absolute monocyte count (AMC) of ≥1 x 10(9)/L defines chronic myelomonocytic leukemia (CMML) but can also be seen in other myeloid disorders including myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN). The presence or development of monocytosis has previously been shown to confer poor prognosis in both primary myelofibrosis (PMF), which is one of the three BCR-ABL1-negative MPN (Leukemia Research 2007;31:1503, Mod Pathol. 2013 Feb;26(2):204) and MDS (Haematologica. 1997;82:25). In the current study, we examined the clinical, prognostic and molecular correlates of monocytosis in PV. Methods Study patients were selected from our institutional database of MPN and fulfilled the 2008 World Health Organization (WHO) criteria for the diagnosis of PV (Blood. 2009;114:937). Cytogenetic and mutational analyses were performed according to conventional methods (Leukemia. 2014;28:2206) any assignment as unfavorable karyotype was per PMF criteria (Leukemia. 2011;25:82). Mutation screening included TET2, ASXL1 and SRSF2 because of their known association with CMML (Leukemia. 2014;28:2206) Statistical analyses considered clinical and laboratory parameters obtained at time of diagnosis. Results Patient characteristics: Analysis was conducted on 587 patients (median age 60 years; 48% males) who met WHO criteria for diagnosis of PV. Amongst them, accurate documentation of AMC was available in 237 patients, cytogenetic information in 239, and ASXL1, TET2 and SRSF2 mutational status in 133 patients. Median (range) values were for AMC 0.6 x 10(9)/L (0-4.7) and leukocytes 11.6 x 10(9)/L (3.8-171.6). 31% of 506 informative patients had palpable splenomegaly, 34% of 551 had microcirculatory symptoms, 30% of 566 had pruritus, 8% of 504 had erythromelalgia, 42% of 581 had hypertension, 9% of 584 had diabetes and 11% of 575 were active tobacco users. 25% of the patients presented with history of thrombosis and 22% developed thrombosis after diagnosis. Cytogenetic findings were abnormal in 19%, of whom 20% were unfavorable. TET2, ASXL1 and SRSF2 mutations were documented in 18%, 11% and 3%, respectively. During follow-up, 224 (38%) patients died and median follow-up for living patients was 109 months. Median survival was 16 years and leukemic or fibrotic transformations were documented in 4% and 14%, respectively. Comparison of patients with and without monocytosis: Among 237 informative patients, 32 (14%) displayed monocytosis (AMC ≥1 x 10(9)/L) at time of diagnosis. PV patients with monocytosis were older (p=0.006) and displayed higher leukocyte count (p<0.0001) and higher incidences of leukocytosis (p=0.024) and unfavorable cytogenetic abnormalities (p=0.02). There was no association between monocytosis and mutations for TET2 (p=0.1), ASXL1 (p=0.7) and SRSF2 (p=0.3) or thrombosis before (p=0.9) or after (p=0.5) diagnosis (p=0.5), palpable splenomegaly (p=0.6), pruritus (p=0.7) or microcirculatory symptoms (p=0.1). Among the 237 PV patients in whom information regarding AMC was available, 70 (30%) died during follow-up and 49 (21%), 23 (10%), 9 (4%) developed thrombosis, leukemic transformation or fibrotic progression, respectively. In univariate analysis, overall (p=0.009; HR 2.0, 95% CI 1.2-3.4) but not leukemia-free (p=0.79), myelofibrosis-free (p=0.13) or thrombosis-free (p=0.48) survivals were different between patients with or without monocytosis. Furthermore, the significant difference in survival was no longer apparent when analysis was adjusted for age (p=0.13), unfavorable karyotype (0.17) or leukocytosis (p=0.06). Conclusions Monocytosis (AMC ≥1 x 10(9)/L) is not infrequent in PV (14%). However, the presence of monocytosis does not appear to represent a significantly different phenotype in terms of molecular characteristics although it is associated with older age, leukocytosis and unfavorable karyotype. The latter associations account for the inferior survival seen in patients with monocytosis. Disclosures No relevant conflicts of interest to declare.