Citations

Background: The 2008 International Working Group for CLL (IWCLL) criteria define MBL as a clonal B-cell disorder with a peripheral blood B-cell count of <5 x 109/L, in the absence of cytopenias(s), lymphadenopathy and/or organomegaly on physical examination, and no other concomitant lymphoproliferative disorder. In the presence of palpable lymphadenopathy and/or organomegaly, and a B-cell count of < 5 x 109/L, a diagnosis of small lymphocytic lymphoma (SLL) is established. A study by Gentile et al (Am J Hematol. 2013) reported that 29 out of 62 individuals with clinically identified MBL (42%) had lymphadenopathy identified on CT imaging. Notably, however, after a median follow-up of 35 months, the rate of progression among cases of MBL with lymphadenopathy identified on CT imaging was only 6.9% (2/29 patients), which was no different than in cases of MBL without lymphadenopathy on CT imaging (rate of progression, 9%; 3/33 patients). Our study sought to 1) determine if lymphadenopathy and/or organomegaly detected by imaging studies performed for unrelated reasons in individuals with MBL can identify a subset with shorter time to first CLL therapy (TFT) and overall survival (OS); and 2) compare outcomes of individuals with MBL who have incidentally detected lymphadenopathy/splenomegaly and SLL patients. Methods: We used the Mayo Clinic CLL Database to identify individuals with high-count MBL (absolute B-cell count: 0.5 - 4.9 x 109/L) and divided them into the following three cohorts: a) Cohort A: no imaging studies available at MBL diagnosis; b) Cohort B: imaging studies done within one year of MBL with no evidence of lymphadenopathy and/or organomegaly; and c) Cohort C: imaging studies done within one year of MBL with lymphadenopathy and/or organomegaly, attributable to MBL. All individuals with MBL were first seen at Mayo Clinic after 1/1/2002; those with a concomitant lymphoproliferative disorder within 3 months of diagnosis were excluded. Patients with SLL seen during the same time interval were identified as a comparison cohort. We compared the baseline characteristics (Kruskal Wallis for continuous and Chi-square for categorical variables) and TFT and OS across the three MBL cohorts, and patients with SLL. Cumulative incidence of TFT was adjusted for the competing risk of death. Age- and sex-adjusted OS was analyzed using inverse weights methods. Results: 657 individuals with high-count MBL with a median follow-up of 6.7 years were identified: 415 (63%) individuals were in Cohort A, 142 (22%) in Cohort B, and 100 in (15%) Cohort C. Compared to Cohort B, individuals in Cohort C were more likely to have unmutated IGHV, high expression of CD38, and higher beta-2 microglobulin level (Table 1). SLL patients were younger, had higher rate of unmutated IGHV, and had high expression of CD49d compared to MBL individuals in Cohort C (Table 1). There was suggestive evidence of a difference in TFT between Cohorts B and C (estimated 10-year treatment rate 28.3% vs. 41.6%; p=0.16; HR 1.62 95% CI 0.84-3.15). TFT was significantly shorter in SLL patients compared to those with Cohort C (estimated 10-year treatment rate 71% vs. 41.6%, respectively, P<0.001; Figure 1A). There was a trend toward shorter OS in Cohort C compared to Cohort B (estimated 10-year OS rate 53.7% vs. 64.2%, respectively, P=0.09; Figure 1B). In contrast, there was no difference in OS among MBL individuals in Cohort C compared to those with SLL (estimated 10-year OS rate 56.9% vs. 62.6%, P=0.72). Summary/Conclusion: Our findings demonstrate that individuals with MBL who have incidentally identified lymphadenopathy/splenomegaly at diagnosis are more likely to have an unfavorable risk profile, shorter TFT and OS compared to patients who did not have lymphadenopathy/splenomegaly at MBL diagnosis. Additionally, these individuals have a longer TFT but similar OS compared to SLL patients seen during the same time interval. If externally validated, these findings have significant implications for individuals with newly diagnosed MBL. Disclosures Ding: Merck: Research Funding; DTRM Biopharma: Research Funding. Kenderian:Novartis: Patents & Royalties, Research Funding; Tolero: Research Funding; Humanigen: Other: Scientific advisory board , Patents & Royalties, Research Funding; Lentigen: Research Funding; Morphosys: Research Funding; Kite/Gilead: Research Funding. Kay:MorphoSys: Other: Data Safety Monitoring Board; Infinity Pharmaceuticals: Other: DSMB; Celgene: Other: Data Safety Monitoring Board; Agios: Other: DSMB. Parikh:AstraZeneca: Honoraria, Research Funding; Janssen: Research Funding; AbbVie: Honoraria, Research Funding; Acerta Pharma: Research Funding; Ascentage Pharma: Research Funding; Genentech: Honoraria; Pharmacyclics: Honoraria, Research Funding; MorphoSys: Research Funding.

Abstract Background: Current prognostication in primary myelofibrosis (PMF) utilizes MIPSS70 (mutation-enhanced international prognostic scoring system for transplant-age patients), MIPSS70+ version 2.0 (karyotype-enhanced MIPSS70) and GIPSS (genetically-inspired prognostic scoring system, which is based on mutations and karyotype) (JCO 2018;36:310; JCO doi: 10.1200/JCO.2018.78.9867; Leukemia. 2018;doi:10.1038/s41375-018-0107). These contemporary models are inter-complimentary and highly efficient in predicting overall survival. However, specific risk factors for very long survival (e.g. 20+ years) and short-term mortality (i.e. death within 5 years of diagnosis) have not been systematically looked into. Methods: Study patients were recruited from the Mayo Clinic, Rochester, MN, USA. Diagnoses were according to the 2016 World Health Organization criteria (Blood. 2016;127:2391). Logistic regression statistics was used to identify predictors of 20-year survival and 5-year mortality. Variables evaluated in the logistic model included those that are currently listed in MIPSS70, MIPSS70+ version 2.0 and GIPSS, as well as age (≤70 vs >70 years) and sex. Receiver operating characteristic (ROC) curves and area under the curve (AUC) were used to estimate predictive accuracy. The JMP® Pro 13.0.0 software from SAS Institute, Cary, NC, USA, was used for all calculations. Results: A total of 1,282 consecutive patients with PMF (median age 65 years, range 19-92; 63% males) were used to identify 26 (2%) patients (median age 51 years, range 28-71; 38% males) who survived their disease for at least 20 years (very long-lived patients) and 626 (49%) patients (median age 68 years, range 27-92; 66% males) who died within 5 years of their diagnosis. Clinically-derived information, including the clinical variables used in MIPSS70 and MIPSS70+ version 2.0, with the exception of fibrosis grade (information available in 60%), was available in 99% of the study population; cytogenetic information was available in 94%, driver mutational status in 71% and the full profile of high molecular risk (HMR) mutations, including ASXL1, SRSF2, U2AF1 Q157, EZH2, IDH1 and IDH2, in 42%. MIPSS70+ version 2.0 risk distribution for the entire study population (n=1,282) was 4% very low risk, 16% low risk, 19% intermediate risk, 40% high risk and 21% very high risk; the corresponding percentages for the 26 very long-lived patients were 14%, 29%, 14%, 43% and 0% and for the 626 short-term survivors were 0%, 4%, 10%, 47% and 39% (p<0.001). Cytogenetic, driver mutation and HMR mutation information was available in 100%, 58% and 27% of the 26 long-term survivors, respectively, and 98%, 63% and 39% of the 626 short-term survivors. Multivariable logistic regression analysis of 20-year survival identified the following seven variables as being favorable: age ≤70 years (p=0.002); female sex (p=0.03); hemoglobin level ≥10 g/dl for women and ≥11 g/dl for men (p=0.03), leukocyte count ≤25 x 109/l (p=0.009), platelet count ≥100 x 109/l (p=0.002), circulating blasts ≤1% (p=0.03) and absence of constitutional symptoms (p=0.04). The particular phenotypic profile exhibited a high degree of predictive accuracy with an estimated AUC of 0.90 (Figure 1a); karyotype and mutations did not retain significance in this particular analysis; in fact, 5 (71%) of the 7 long-term survivors who were informative harbored at least one HMR mutation. A similar analysis for 5-year mortality identified the following risk factors: high molecular risk mutations (p<0.001); unfavorable or very high risk karyotype (p<0.001); absence of type 1/like CALR mutations (p<0.001); age >70 years (p<0.001); constitutional symptoms (p<0.001); hemoglobin level <10 g/dl for women and <11 g/dl for men (p<0.001); leukocyte count >25 x 109/l (p=0.004); and circulating blasts >1% (p=0.001); predictive accuracy was estimated at AUC 0.87 (Figure 1b). Conclusions: The phenotypic profile of long-lived patients in PMF includes young age (≤70 years old), female sex, asymptomatic disease (i.e. no constitutional symptoms) and absence of moderate to severe anemia, thrombocytopenia or leukocytosis and ≤1% circulating blasts; each one of these parameters, with the exception of female sex, were present in ≥80% of long-term survivors. Karyotype and mutations were more relevant in predicting short-term mortality. Disclosures No relevant conflicts of interest to declare.

Abstract Background: Anagrelide clinical trials in myeloproliferative neoplasms (MPN) were pioneered by the late Murray N. Silverstein M.D.(1928-1998) of the Mayo Clinic and the first publication involving 20 patients, including 17 with essential thrombocythemia (ET), appeared in 1988 (study launched in October 1985) (N Engl J Med 1988;318:1292). A larger study involving 577 patients, including 335 with ET, was subsequently published in 1992 and led to FDA approval in March 1997 (Am J Med 1992;92:69). Anagrelide has also been evaluated, in controlled studies, for its efficacy and safety as first-line therapy for ET; the results of these studies suggested that anagrelide was not inferior to hydroxyurea, in one study (Blood 2013;121:1720), but might have been harmful to patients in, the second study (N Engl J Med 2005;353:33); in the latter study, patients receiving anagrelide experienced higher incidences of arterial thrombosis, bleeding complications and fibrotic progression. These observations raised significant concern regarding an adverse survival impact of anagrelide in ET; unfortunately, the follow-up period of formal controlled studies were too short to accurately address the particular concern. Methods: The current study represents a retrospective examination of the potential impact of anagrelide therapy on survival and disease complication rates in ET. The study population was recruited from a consecutive cohort of adult patients (age ≥18 years) with MPN seen at the Mayo Clinic from 10/27/1967 through 12/29/2017. Diagnosis and determinations of fibrotic and/or leukemic transformations, were in strict accordance with the 2016 World Health Organization criteria (Blood 2016;127:2391). Statistical analyses were based on clinical and laboratory parameters obtained at the time of first referral to the Mayo Clinic which, in the majority of cases, coincided with initial diagnosis. All patients were followed from diagnosis until death or date of last follow-up or contact. Follow-up was until April 2018 and data collected via medical records or in certain cases, by directly contacting patients or their physicians. Survival and time-to-event curves were prepared using the Kaplan-Meier method and compared by the log-rank test. The JMP® Pro 13.0.0 software package was used for all analyses (SAS Institute, Cary, NC, USA). Results: 1,076 patients with ET were considered (median age 58 years; females 63%); international prognostic scoring system for ET (IPSET; Blood 2012;120:1197) risk distribution was 28% high, 42% intermediate and 30% low; driver mutational status was JAK2 61%, CALR 25%, triple-negative 11% and MPL 3%. Comparison of cases diagnosed before (n=433) and after (n=643) the FDA approval date of anagrelide (1997) revealed the former cohort to be younger (median 57 vs 60 years; p=0.003), although the difference in IPSET risk distribution was not significant (p=0.14). Figures 1a, 1b, 1c and 1d illustrate overall (OS), myelofibrosis-free (MFFS), leukemia-free (LFS) and thrombosis-free survival data comparing ET patients diagnosed before and after the 1997 FDA approval date for anagrelide; a significant difference was apparent for OS (p=0.006; HR 1.4, 95% CI 1.1-1.7) and MFFS (p<0.001; HR 4.2, 95% CI 2.7-6.5), in favor of patients diagnosed prior to 1997; during multivariable analysis that included IPSET and sex, the significant difference in both OS and MFFS were sustained; the difference in OS was most apparent after the first decade of diagnosis with 10- and 20-year survival rates of 75% and 50% for diagnosis prior to 1997 vs 72% and 21% for diagnosis between 1997 and 2017 (figure 1a); the 10- and 20-year risk of fibrotic progression was 3% and 15% for diagnosis prior to 1997 and 14% and 46% for diagnosis after 1997 (figure 1b); there was no impact on LFS (p=0.32; Figure 1c) or TFS (p=0.18; Figure 1d). Similarly stratified survival data in polycythemia vera (n=665) and primary myelofibrosis (n=1,282) showed no impact on survival (p=0.3 and 0.17, respectively). Conclusions: In a retrospective, but otherwise unbiased comparative analysis, we show significantly decreased OS and MFFS in ET patients diagnosed after the FDA approval date of anagrelide (1997); the increased risk of fibrotic progression noted is consistent with results of earlier prospective data (N Engl J Med 2005;353:33). Our observations regarding OS requires confirmation in a prospective controlled setting. Disclosures No relevant conflicts of interest to declare.

Abstract Background : Extramedullary hematopoiesis (EMH) implies the production of erythroid and myeloid progenitor cells outside of the bone marrow. EMH in adults is typically seen in patients with myeloproliferative neoplasms (MPN). The current study examines the Mayo Clinic experience with EMH cited in the absence of MPN. The objectives were to describe associated conditions and involved sites and identify "idiopathic" cases and review their management and long-term outcome. Methods : After approval by the Mayo Clinic institutional review board, institutional databases were screened through the Mayo Clinic Advanced Cohort Explorer (ACE) Tool, in order to identify patients with EMH. We performed a retrospective database review of all identified patients between 1975 and 2018. Demographic, biochemical, genetic, radiological and pathological data were collected and reviewed. Results : ACE identified 1,933 cases of "EMH". Extensive review confirmed the absence of associated MPN in 336 cases. Among these, 27 cases involved pathology remarks during tissue biopsy for liver transplant and were excluded from further analysis. The most frequent associated conditions in the remaining 309 cases included myelodysplastic syndromes (n=41; 13%), acute myeloid leukemia (n=28; 9%), hemolytic anemia (n=24; 8%), thalassemia (n=22; 7%), non-Hodgkin's lymphoma (n=19; 6%), immune thrombocytopenic purpura (n=17; 6%), metastatic cancer (n=17; 6%), plasma cell neoplasms (n=12; 4%) and a spectrum of other hematologic and non-hematologic conditions, including chronic lymphocytic leukemia, natural killer cell disorders, Hodgkin's lymphoma and Hemophagocytic lymphohistiocytosis. in 12 (4%) cases, no overt associated condition was evident and the cases were accordingly assigned "idiopathic". The most frequent involved sites included spleen (n=162), liver (n=78) and lymph nodes (n=20). A diagnosis of "idiopathic" EMH was established in 12 (4%) patients (median age 71 years, range 23-78; 50% females). Most of these cases presented with non-specific symptoms including abdominal and back pain and the EMH was an incidental discovery (Table 1). Involved sites included 4 pre-sacral, 3 para-spinal, 2 spleen and one each retroperitoneal, pleural-based chest mass and right upper lobe lung mass. All cases were evaluated with imaging studies and diagnosis was subsequently confirmed by pathology review. Past medical history was non-contributory. Complete blood counts were normal in 7 cases, showed anemia in 4 cases and were not available in one case (Table 1). The median follow-up time since the discovery of EMH was 7 years (range 2-20). None of the patients showed evidence of any malignancy, including MPN or other hematologic disorders, either at presentation or during follow-up. Nine (75%) of the 12 patients were managed conservatively; the two patients with splenic EMH underwent splenectomy and one patient had surgical excision of the EMH mass in order to prevent compression of the ureter. The FUO in the patient with splenic EMH resolved with splenectomy. Conclusions : We present the largest experience in EMH without associated MPN, in adults. We describe associated conditions and elaborate further on "idiopathic" EMH (n=12), which often represented an incidental discovery during evaluation of unrelated symptoms. None of the patients with idiopathic EMH harbored occult malignancies or subsequently developed MPN or other myeloid malignancies. Our observations do not support undertaking extensive investigations targeting MPN or other malignancies in idiopathic EMH and simple monitoring might be adequate. Disclosures No relevant conflicts of interest to declare.

Abstract Background : Cytogenetic abnormalities occur in approximately a third of patients with primary myelofibrosis (PMF) and 5-20% of those with essential thrombocythemia (ET) or polycythemia vera (PV). Abnormal karyotype in PV and specific cytogenetic abnormalities in PMF have been shown to adversely affect survival (Leukemia. 2018;32:1189; Br J Haematol. 2017 Jun 9. doi: 10.1111/bjh.14798). In the current retrospective study, we considered 650 Mayo Clinic patients with myeloproliferative neoplasms (MPN), including ET, PV and PMF, with at least two documented bone marrow (BM) biopsies, in order to examine the incidence and pattern of changes in karyotype and their clinical correlates. Methods : Study patients were recruited from the Mayo Clinic, Rochester, MN, USA, based on documentation of at least two serial BM biopsies. Diagnoses were according to the 2016 World Health Organization criteria (Blood. 2016;127:2391). BM biopsy #1 referred to the baseline karyotype at time of initial diagnosis/referral and BM biopsy #2 to the first repeat BM biopsy after diagnosis. In addition to documenting the presence or absence of changes in karyotype, a notation was made regarding disease phase, at the time of the repeat biopsy, in order to allow accurate interpretation of the data and evaluation of survival impact. Results: 650 patients with MPN, including 153 ET, 105 PV and 392 PMF, were included in the current study and had undergone at least two BM biopsies; 227 patients had three, 108 four, 48 five, 19 six, and 4 seven repeat BM biopsies during their clinical course. Cytogenetic clonal evolution in patients with normal karyotype at baseline : Baseline karyotype was normal in 466 (72%) patients, including 139 (91%) ET, 91 (87%) PV and 236 (60%) PMF. Clonal evolution, which constituted a change from "normal" to "abnormal" karyotype, was documented in 16 (12%) patients with ET, 22 (24%) with PV and 75 (33%) with PMF; the latter included favorable karyotype in 11% of the cases, unfavorable in 12% and very high risk (VHR) in 10%. 11 (69%) of the 16 documented cases of clonal evolution in ET, 10 (45%) of 22 in PV and 11 (15%) of 75 in PMF were accompanied by clinically evident progression to blast or fibrotic phase disease, at the time of the repeat BM biopsy. Cytogenetic clonal evolution in patients with abnormal karyotype at baseline : Baseline karyotype was abnormal in 187 (28%) patients, including 17 (9%) ET, 14 (13%) PV and 156 (40%) PMF. Additional changes in karyotype, during serial BM biopsies, were documented in 6 (35%) ET, 5 (36%) PV and 71 (46%) PMF patients. In PMF, the pattern of changes in karyotype included "favorable" to "favorable" in 7%; "favorable" to "unfavorable" in 13%; "favorable" to "VHR" in 5%; "unfavorable" to "unfavorable" in 13%; "unfavorable" to "VHR" in 3%; and "VHR" to "VHR" in 6%. All 11 (100%) patients with ET or PV who underwent clonal evolution displayed clinically overt disease transformation into leukemic or fibrotic phase disease, at the time of the repeat BM biopsy. Leukemic transformation at the time of the repeat BM biopsy was evident in 13 (18%) of the 71 PMF cases with clonal evolution. Survival impact of cytogenetic clonal evolution without change in disease phase : The survival impact of cytogenetic clonal evolution was examined under the following provisions: i) analysis was limited to events occurring at BM biopsy #2 with survival calculated from the date of BM biopsy #2; ii) patients with leukemic or fibrotic transformation at time of BM biopsy #2 were excluded from analysis; and iii) clonal evolution for the purposes of survival analysis constituted changes from "normal" to "abnormal", for ET and PV, while the type of changes were taken under consideration for PMF. Under these stipulations, clonal evolution appeared to affect survival in general, although statistical significance was apparent for only ET and PMF (Figures 1a, 1b and 1c). Conclusions: Cytogenetic clonal evolution in ET and PV is infrequent, in the absence of clinically overt disease transformation, and is more likely to occur in PMF. Such events, when documented in chronic phase disease, appeared to predict shortened survival in all three MPNs, which was most apparent in ET and with emergence of VHR or unfavorable abnormalities in PMF. These observations warrant prospective studies that account for indication bias. Disclosures No relevant conflicts of interest to declare.

Abstract Introduction: Heparin-induced Thrombocytopenia (HIT) is a potentially life and limb threatening pro-thrombotic syndrome triggered by antibodies to platelet factor 4 (PF4)/polyanion complexes. Commonly used screening tests such as the PF4/Heparin ELISA (PF4 ELISA), while easy to perform in the near-patient setting, are highly non-specific. In contrast, more accurate tests such as the serotonin release assay (SRA) are technically complex, require radioactivity and are performed in only a handful of reference laboratories. These diagnostic challenges lead to both unnecessary anticoagulant use as well as avoidable cases of severe bleeding. Recent reports suggest that a relatively simple three-hour flow cytometry-based test that uses PF4-treated normal platelets, the PEA (PF4-dependent p-selectin Expression Assay), is at least as accurate as the SRA for identifying patients who have HIT (Thromb Haemost. 2015 Nov 25;114(6):1322-3; Chest. 2016 Sep;150(3):506-15; Chest. 2017 Oct;152(4):e77-e80). Here we describe results of a large prospective study designed to compare the accuracy of the SRA and PEA for HIT diagnosis in a clinical setting. Methods: The PEA and SRA were performed on serum samples obtained from adult patients (≥18 yrs.) from 2 large tertiary care academic hospitals from May 2016 to Sep 2017. All inpatients for whom PF4 ELISA testing was ordered were included in the study. The PEA was performed with platelets pretreated with PF4 at 3 concentrations: 30mcg/mL (PEA30), 10mcg/mL (PEA10) and 3mcg/mL (PEA3). Sera were batch-tested in both assays (SRA and PEA) using the same target platelets. The central laboratory was blinded to clinical history and to the results of the PF4 ELISA performed by participating hospitals at the time of diagnosis. Both centers performed IgG-specific PF4 ELISAs and utilized manufacturer-recommended cut-offs for positivity. Predefined "more-stringent" and "less stringent" criteria based on clinical findings (4Ts score) and results of PF4 ELISA testing were used to define the likelihood of a patient having HIT (Table 1A). Receiver Operating Curve (ROC) analysis was performed and Area Under the Curve (AUC) of each assay was calculated to assess their diagnostic accuracy. Since high test specificity was desired, positive cut-offs that maximized the sum of sensitivity and specificity in a specificity range of ≥90% and ≥95% were derived. To evaluate non-inferiority of the PEA to the SRA, we assessed whether the lower limit of the one-sided 95% confidence interval of the ΔAUC (PEA-SRA) was higher than a non-inferiority margin of 5% and 10%. Results: A total of 440 patient samples were tested with both assays. Seventeen and 28 patients were classified as having true HIT based on the use of the more- and less-stringent criteria, respectively. When classified by more-stringent criteria, the AUC was numerically greater for each of the three PEA tests than for the SRA (Table 1B). All tests had excellent accuracy (AUC>0.90, "excellent" by the Traditional academic point system). Using less-stringent criteria, the PEA30 had the highest AUC estimate followed by the SRA (Table 1C). Positive cut-offs generated at test specificities of ≥90% and ≥95% using data classified by more stringent criteria are shown in Table 1D. PEA3 was non-inferior to the SRA at a 5% non-inferiority margin, and all PEA tests were non-inferior at the 10% margin using the more stringent classification for true HIT (Fig 1A). In the less-stringently classified data set, the PEA30 was non-inferior to the SRA at a 10% margin (Fig 1B). Conclusions: The PEA, a 3-hour, non-radioactive functional HIT assay demonstrated high diagnostic accuracy and was non-inferior to the SRA using commonly accepted non-inferiority margins for diagnostic testing (5-10%). The technical advantages of the PEA over the SRA may encourage its widespread adoption as a rapid-turnaround, accurate and near-patient diagnostic for patients with suspected HIT. Disclosures Jones: BloodCenter of Wisconsin: Patents & Royalties. Curtis:Ionis Pharmaceuticals: Consultancy. Bougie:BloodCenter of Wisconsin: Patents & Royalties. Aster:BloodCenter of Wisconsin: Patents & Royalties. Garcia:Shingoi: Consultancy; Retham Technologies LLC: Consultancy; Incyte: Research Funding; Daiichi Sankyo: Research Funding; Bristol Meyers Squibb: Consultancy; Portola: Research Funding; Janssen: Consultancy, Research Funding; Pfizer: Consultancy; Boehringer Ingelheim: Consultancy. Padmanabhan:BloodCenter of Wisconsin: Patents & Royalties: Patent/royalties for HIT diagnostic testing; Veralox Therapeutics: Other: Advisory Board; Retham Technologies LLC: Equity Ownership, Other: Retham seeks to develop HITDx(TM), a new assay for HIT diagnosis; TerumoBCT: Consultancy; GE Healthcare: Other: Material support for Clinical Quality Improvement Initiative; Janssen Pharmaceuticals: Consultancy.

Abstract Background : Survival prediction in essential thrombocythemia (ET) and polycythemia vera (PV) is currently based on clinically-derived risk variables, including age, thrombosis history and leukocyte count (Blood. 2012;120:1197; Leukemia. 2013;27:1874). We have previously reported on the prognostic contribution of mutations, in both ET and PV (Blood Adv. 2016;1:21). The current study examines the possibility of integrating genetic and clinical information for predicting overall (OS), leukemia-free (LFS) and myelofibrosis-free (MFFS) survival in ET and PV. Methods : Study patients were recruited from the Mayo Clinic, Rochester, MN, USA and the University of Florence, Florence, Italy, based on availability of next-generation sequencing (NGS)-derived mutation information. Diagnoses were according to the 2016 World Health Organization criteria (Blood. 2016;127:2391). NGS-detected coding region variants were filtered through the Exome Aggregation Consortium (ExAC) database and annotated by the Catalogue of Somatic Mutations in Cancer (COSMIC) database as mutants or variants of uncertain significance (VUS). Conventional statistics was employed for outcome analysis and assessment of model performance. Results: 906 molecularly-annotated patients (416 from Mayo and 490 from Florence), including 502 ET and 404 PV cases, were included in the current study. The Mayo/Florence cohorts included 270/232 ET (median age 57/54 years, 60%/59% females) and 146/258 PV (median age 63/58 years, 52%/44% females) patients; median follow-up was 9.9/12.9 years for ET and 10.7/12.4 years for PV; during this time 39%/38% deaths and 4.4%/6.5% leukemic and 16%/33% fibrotic progressions were documented for ET, with the corresponding figures for PV being 50%/26%, 4.8%/3% and 13%/36%. Cytogenetic information was available in 84%/63% ET and 80%/49% PV cases in the Mayo/Florence cohorts. In both Mayo and Florence cohorts, multivariable analysis of mutations identified primarily spliceosome mutations to adversely affect OS (SF3B1 and SRSF2 in ET and SRSF2 in PV) and MFFS (U2AF1 and SF3B1 in ET); in addition, TP53 mutations was associated with leukemic transformation in ET, in both patient cohorts. Other mutations with independently significant contribution, validated in one but not both cohorts, included EZH2 (OS and LFS in ET), IDH2 (OS and LFS in PV) and RUNX1 (LFS in PV and ET). For the purposes of the current study, mutations considered "adverse" for subsequent analysis and development of prognostic models required validation in both Mayo and Florence cohorts. Age-adjusted, all-inclusive multivariable analysis of genetic and clinical variables identified the following as independent risk factors for OS, in both Mayo and Florence cohorts: ET ─ SRSF2/SF3B1 mutations, age >60 years and male sex; PV ─ SRSF2 mutations, age >67 years and leukocyte count ≥11 x 109/l. In addition, multivariable analysis flagged leukocytosis in ET (Florence cohort only) and abnormal karyotype in PV (Mayo cohort only) as additional factors. Development of mutation-enhanced international prognostic systems for ET and PV In order to optimize the number of informative cases, the two Mayo and Florence databases were subsequently combined and subjected to multivariable analysis that confirmed the independent survival effect, in ET, of SRSF2/SF3B1 mutations (HR 2.8, 95% CI 1.8-4.3), age >60 years (HR 6.7, 95% CI 4.8-9.4) and male sex (HR 1.8, 95% CI 1.4-2.4) and, in PV, of SRSF2 mutations (HR 7.0, 95% CI 2.3-17.4), age >60 years (HR 5.7, 95% CI 3.3-10.1), and leukocyte count ≥11 x 109/l (HR 2.4, 95% CI 1.5-3.9); the combined analysis also flagged independent prognostic contribution from abnormal karyotype in PV (HR 2.1, 95% CI 1.1-3.6). HR-weighted risk point allocation resulted in new, mutation-enhanced 4-tiered risk models for ET (MIPSS-ET based on mutations, age and sex; figure 1a) and PV (MIPSS-PV based on mutations, karyotype, leukocyte count and age; figure 1b). Both models displayed high predictive accuracy and were internally validated by bootstrapping. The combined analysis also confirmed the impact of TP53 mutations on LFS (figure 1c) and U2AF1/SF3B1 mutations on MFFS (figure 1d), in ET. Conclusions: Spliceosome mutation information enhances survival prediction in ET and PV and identifies those at risk for fibrotic progression. TP53 mutations predict leukemic transformation in ET. Disclosures No relevant conflicts of interest to declare.