Background: Risk assessment models (RAMs) are relevant approaches to identify cancer outpatients at high risk of venous thromboembolism (VTE). Among the proposed RAMs, the Khorana (KRS) and the new-Vienna CATS risk scores have been externally validated in ambulatory patients with cancer.Objectives: To test KRS and new-Vienna CATS scores in 6-month VTE prediction and mortality in a large prospective cohort of metastatic cancer outpatients during chemotherapy.Patients/Methods: Newly diagnosed patients with metastatic non-small cell lung, colorectal, gastric, or breast cancers were analyzed (n = 1286). The cumulative incidence of objectively confirmed VTE was estimated with death as a competing risk and multivariate Fine and Gray regression.Results: Within 6 months, 120 VTE events (9.7%) occurred. The KRS and the new-Vienna CATS scores showed comparable c-stat. Stratification by KRS provided VTE cumulative incidences of 6.2%, 11.4%, and 11.5% in the low-, intermediate-, and high-risk categories, respectively (p = ns), and of 8.5% vs. 11.8% (p = ns) in the low-vs. high-risk group by the single 2-point cut-off value stratification. Using a pre-defined 60-point cut-off by the new-Vienna CATS score, 6.6% and 12.2% cumulative incidences were obtained in the low-and high-risk groups, respectively (p < 0.001). Furthermore, having a KRS =2 = or a new-Vienna CATS score >60 points was also an independent risk factor for mortality.Conclusion: In our cohort, the 2 RAMs showed a comparable discriminating potential; however, after the application of cut-off values, the new-Vienna CATS score provided statistically significant stratification for VTE. Both RAMs proved to be effective in identifying patients at increased risk of mortality.

BACKGROUND:Polycythaemia vera is a myeloproliferative neoplasm characterised by a high incidence of thrombosis. The contribution of platelets, key players in haemostasis, in this setting is still unclear. So far, the majority of studies have been focussed on specific platelet abnormalities but not on their actual capacity to form thrombi. The aim of this study was to characterise, ex vivo under flow conditions, the capacity of platelets from patients with polycythaemia vera to adhere to collagen and induce thrombus formation.MATERIALS AND METHODS:Thirty-nine patients and 30 healthy controls were studied. Thrombus formation was induced by perfusing whole blood over a collagen-coated surface, in a parallel-plate flow chamber coupled to a fluorescent microscope. This dynamic system enables platelet adhesion and thrombus formation to be followed in real time and also allows measurements of the extent of the thrombus and platelet surface antigen expression. Laboratory data were analysed in the light of the patients' main haematological parameters and therapies.RESULTS:Platelet adhesion was significantly greater in patients than in control subjects. Patient thrombi were usually larger and more complex than those formed by control platelets. A significant positive correlation was found between platelet adhesion and both the haematocrit and red blood cell count. These parameters remained significantly correlated with platelet adhesion also after multivariable analysis adjusted for gender, age, therapy and JAK2V617F allele burden. Furthermore, subjects with a haematocrit >45% had significantly greater platelet adhesion than subjects with a haematocrit <45%.DISCUSSION:Our data indicate that increased platelet adhesion participates in the thrombotic diathesis of patients with polycythaemia vera, and that the haematocrit level can affect the adhesive and thrombus forming capacities of platelets.

These investigations indicate that ponatinib treatment increases gene expression of aortic prothrombotic and platelet signalling genes that promote GPVI activation. Addition of pioglitazone reduces the prothrombotic characteristics conferred by ponatinib treatment. These data indicate that cancer-associated thrombosis can be managed by non-anticoagulant pharmacologic agents.

Background: Severe COVID-19 is associated with a profound derangement of the hemostatic system characterized by hypercoagulability, complement activation and endothelial cell perturbation. After disease resolution, some convalescent subjects still experience post-COVID-19 symptoms. No information is available on persistence of hemostatic alterations in this setting. Bergamo city, represents one of the first and most affected area by SARS-CoV-2 infection in the world. For this reason, since the beginning we were actively involved in hyperimmune plasma collection from COVID-19 convalescent subjects. Aims: In this study, in a large cohort of convalescent donors of hyperimmune plasma, we aimed to characterize select hemostatic parameters of hypercoagulability and endothelial cell perturbation and their association with disease severity, demographic characteristics, and antibody levels. Methods: Recovered COVID-19 patients eligible to plasma donation were tested for the SARS-CoV-2 antibodies by the anti-N IgG SARSCoV- 2 antibodies (Abbott Laboratories, IL, USA, Anti-N Abs), and/or the anti-S IgG SARS-CoV-2 antibodies (Liaison-Diasorin, Sallugia-VC, Italy, Anti-S Abs), according to the manufacturer's instructions. Fibrinogen, protein C, protein S, factor V, factor VIII, factor XIII, D-dimer, and von Willebrand factor (vWF) were assessed. Results: 425 subjects have been included (275M/150F) with a median age of 48 years (range: 19-67 years). Among convalescent subjects admitted to the donation, male gender, age > 40 years, and previous hospitalization for COVID-19, were identified as independent predictive factors for significantly (p<0.001) higher levels of SARS-CoV-2 IgG (both anti-S and anti-N). Hemostatic parameters including fibrinogen, protein S, factor V, factor VIII, factor XIII, and D-dimer were not different between severe and non-severe COVID-19. Differently, convalescent subjects with previous severe COVID-19 showed significantly higher levels of vWF (124±40 vs 121±41 %, p<0.001) and PC (119±19 vs 109±19 %, p<0.001) compared with non-severe COVID-19 subjects. In addition, significant positive correlations were found between vWF levels and anti-S Abs (vWF antigen r=0.216;vWF activity r=0.257 and vWF RiCof r=0.226, p<0.01). Summary/Conclusion: Our data show that gender, age and severe disease can be potential predictors of an increased immunological response. Furthermore, convalescent subjects show a persistently high vWF levels, suggesting a persistence of the endothelial activation, despite of clinical disease remission.

Introduction: Severe COVID-19 patients present with a hypercoagulable state, complement activation and endothelial perturbation, which result from an excessive inflammatory response. Thromboinflammation is one important mechanism underlying the COVID-19-associated coagulopathy and the increased risk of thrombosis. Bergamo city is one of the first and most affected area by SARS-CoV-2 infection in the world. For this reason, since the beginning we were actively involved in recruiting convalescent COVID-19 patients, in a program of selection of candidates for convalescent plasma donation. In a large cohort of convalescent COVID-19 patients, we aimed to characterize markers of coagulation activation and endothelial perturbation, in order to explore whether the COVID-19-related hemostasis activation might persist afterwards and evaluate its possible association with the degree of severity of the previous infection, and/or with demographic characteristics, or anti-SARS-CoV-2 antibody levels. Methods: In 392 convalescent COVID-19 patients (216M/176F, median age: 46 years) plasma levels of fibrinogen, protein C, protein S, factor V, factor VIII, factor XIII, D-dimer, von Willebrand factor (vWF), prothrombin fragment F1+2 were measured at the recruitment, i.e. 1-5 months from recovery. Samples were tested for the anti-SARS-CoV-2 antibodies, including anti-S IgG (Anti-S Ab) and anti-N IgG (Anti-N Ab) antibodies at enrollment and at each scheduled subsequent visits. Results: Levels of fibrinogen, D-dimer, von Willebrand factor, protein S and protein C were significantly higher (p<0.05) in patients who were hospitalized for severe COVID-19 as compared to patients who were treated at home. There was no correlation between levels of coagulation biomarkers and days from end of symptoms. Male gender, age > 40 years, and severe form of COVID-19 were identified as independent predictors of high levels of both anti-S and anti-N Ab (p<0.001). Among hemostatic biomarkers, fibrinogen (p<0.01) and vWF (p<0.05) independently predict high levels of anti-S Ab. In particular, vWF levels positively correlated with anti-S Ab levels (vWF-antigen r=0.188; vWF-activity r=0.241 and vWF-RiCof r=0.223, p<0.01). Evaluation of anti-SARS-CoV2 antibody levels at different time points during follow up revealed that 30% of patients displayed high levels of anti-S Ab until more than 8 months from the end of symptoms. Conclusions: Convalescent patients, with a history of severe COVID-19 had a persistent endothelium activation, despite of disease clinical remission even after 9 months from end of symptoms. Furthermore, fibrinogen and vWF levels predicted high levels of Anti-S Ab. Among demographic characteristics, gender, age and severe disease can be predictors of increased antibody response. These findings suggest that inflammation, coagulation and endothelial dysfunction may persist after recovery and may explain the findings of persistent clinical symptoms reported in these patients after healing from COVID-19. Disclosures Falanga: Bayer: Honoraria; Leo Pharma: Honoraria; Pfizer: Honoraria; Sanofi: Honoraria.

Background: Hypercoagulability, complement activation and endothelial perturbation characterize sever COVID-19. After disease remission, a proportion of convalescent subjects still experience post-COVID-19 symptoms. No information is available on persistence of hemostatic alterations in this setting. Bergamo city, represents one of the first and most affected area by SARS-CoV-2 infection in the world. For this reason, since the beginning we were actively involved in recruiting CCP donors. Aims: In a large cohort of CCP donors, we aimed to characterize biomarkers of hypercoagulability and of endothelial perturbation in order to find associations with disease severity, demographic characteristics, and anti-SARS-CoV-2 antibody levels. Methods : Candidate CCP donors were tested for the anti-SARSCoV-2 antibodies, including anti-S IgG antibodies (Anti-S Ab) and anti-N IgG antibodies (Anti-N Ab). In addition, the following plasma biomarkers were assessed: fibrinogen, protein C, protein S, factor V, factor VIII, factor XIII, D-dimer, and von Willebrand factor (vWF). Results: 425 CCP candidates (275M/150F, age range 19-67 years) were admitted to donation. Male gender, age > 40 years, and severe form of COVID-19 were identified as independent predictors of high levels of both anti-S and anti-N Ab ( p <0.001). Among hemostatic parameters, levels of vWF antigen, vWF activity and protein C were significantly higher in CCP donors who had severe COVID-19 compared to donors who had non-severe COVID-19 ( p <0.001). Furthermore, vWF levels positively correlated with anti-S Ab levels (vWF-antigen r=0.216 vWF-activity r=0.257 and vWFRiCof r=0.226, p <0.01). Conclusions: Our data show that gender, age and severe disease can be predictors of an increased immunological response. Furthermore, convalescent subjects show a persistently high vWF levels, suggesting a persistence of the endothelial activation, despite of clinical disease remission.

Background Cancer patients present with a hypercoagulable state often associated with poor disease prognosis. Objectives This study aims to evaluate whether thrombin generation (TG), a global coagulation test, may be a useful tool to improve the identification of patients at high risk of early disease recurrence (ie, E-DR within 2 years) after breast cancer surgery. Patients/Methods A cohort of 522 newly diagnosed patients with surgically resected high-risk breast cancer were enrolled in the ongoing prospective HYPERCAN study. TG potential was measured in plasma samples collected before starting systemic chemotherapy. Significant predictive hemostatic and clinic-pathological parameters were identified in the derivation cohort by Cox regression analysis. A risk prognostic score for E-DR was generated in the derivation and tested in the validation cohort. Results After a median observation period of 3.4 years, DR occurred in 51 patients, 28 of whom were E-DR. E-DR subjects presented with the highest TG values as compared to both late-DR (from 2 to 5 years) and no relapse subjects (P < .01). Multivariate analysis in the derivation cohort identified TG, mastectomy, triple negative and Luminal B HER2-neg molecular subtypes as significant independent predictors for E-DR, which were utilized to generate a risk assessment score. In the derivation and validation cohorts, E-DR rates were 2.3% and 0% in the low-risk, 10.1% and 6.3% in the intermediate-risk, and 18.2% and 16.7%, in the high-risk categories, respectively. Conclusions Inclusion of TG in a risk-assessment model for E-DR significantly helps the identification of operated breast cancer patients at high risk of very early relapse.

Background. Hypercoagulability, a common finding in cancer patients, is associated with an increased risk of both thrombosis and tumor development. The HYPERCAN study (ClinicalTrials.gov, ID# NCT02622815) is an ongoing Italian prospective, multicenter, observational study, evaluating the predictive value of thrombotic markers for early cancer diagnosis in healthy subjects and for cancer prognosis and venous thromboembolism in patients with newly diagnosed malignant disease. In this analysis of a large cohort of patients with breast cancer, we evaluated whether pre-chemotherapy thrombotic biomarker levels: 1. are associated with breast cancer-specific clinicopathological features; and 2. may predict for disease recurrence (DR). Patients and Methods. D-dimer, fibrinogen, prothrombin fragment 1+2 (F1+2), and FVIIa/antithrombin complex (FVIIa/AT) levels were measured in 701 early-stage resected breast cancer patients, candidate to adjuvant chemotherapy and prospectively enrolled in the HYPERCAN study. Significant prognostic parameters for DR were identified by Cox-regression multivariate analysis and used for generating a risk assessment model. The study protocol is approved by the local Ethics Committee. Informed written consent is obtained from all study subjects. Results. Increased pre-chemotherapy D-dimer, fibrinogen, and F1+2 levels were significantly associated with a large tumor size (≥ 5 cm) and lymph node positivity. After 3.4 years follow-up, 71 patients experienced a DR. Comparison of the levels of the hypercoagulation variables of patients who experienced relapse versus patients who remained disease-free during follow-up showed that there were no statistical differences for all, but F1+2 biomarker levels, which were significantly higher in the group patients who relapsed [223 (115-618) vs 197 (115-385) pmol/l; p=0.024]. In addition, correlation analyses showed that pre-chemotherapy levels of fibrinogen were significantly and inversely associated with time to relapse (β = -0.317; p=0.012). Cox-multivariate analysis identified F1+2 (HR 2; 95% CI, 1.1-3.6; p=0.019), tumor size ≥ 5cm (HR 2.6; 95% CI, 1.4-4.6; p=0.001), and Luminal B HER2-neg or TN molecular subtypes (HR 3.9; 95% CI, 2.1-7.5; p<0.001) as independent risk factors for DR. Based on these variables, we generated a risk assessment model that significantly identified patients at low- versus high-risk of DR (cumulative incidence: 6.2 vs 20.7%; HR=3.5; p<0.001). Conclusion. Our prospective laboratory data from the HYPERCAN breast cancer subjects were essential for generating a scoring model for DR risk assessment. Future investigations addressing the role of plasma thrombotic biomarkers in breast cancer patients' management are warranted and may provide the rationale for development of new therapeutic strategies. Project funded by AIRC "5xMILLE Multiunit extension program" n. 12237 grant from the "Italian Association for Cancer Research (AIRC)". Disclosures Santoro: Bayer: Consultancy, Speakers Bureau; Amgen: Speakers Bureau; BMS: Consultancy; Sandoz: Speakers Bureau; Eisai: Consultancy, Speakers Bureau; Novartis: Speakers Bureau; Lilly: Speakers Bureau; Celgene: Speakers Bureau; Servier: Consultancy, Speakers Bureau; Gilead: Consultancy, Speakers Bureau; AstraZeneca: Speakers Bureau; Roche: Speakers Bureau; Abb-Vie: Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; Arqule: Consultancy, Speakers Bureau; MSD: Speakers Bureau; Takeda: Speakers Bureau; BMS: Speakers Bureau.

Introduction: The occurrence of venous thromboembolism (VTE) during chemotherapy may result in treatment delays with unfavorable effects on cancer outcome, therefore VTE prevention is a relevant issue. Current guidelines recommend primary thromboprophylaxis in select high-risk cancer outpatients undergoing chemotherapy. Hence, the use of risk assessment models involving both clinical and biological parameters is increasingly important. In this analysis, in a large prospective cohort of patients with newly diagnosed metastatic non-small cell lung (NSCLC), colorectal (CRC), gastric (GC) or breast (BC) cancers, we assessed whether pre-chemotherapy levels of thrombotic biomarkers may help to stratify patients at different risk levels of VTE during the first 6 months of anti-tumor therapy. Methods: The study cohort included patients with advanced cancer enrolled from January 2012 to December 2017 in the HYPERCAN study (ClinicalTrials.gov, ID# NCT02622815), an ongoing Italian prospective, multicenter, observational study (Falanga et al, Thromb Res 2016). Clinical data and blood samples were collected at enrollment and during scheduled follow-up visits. Baseline plasma levels of fibrinogen (Clauss method), d-dimer (immunoturbidimetric assay), prothrombin fragment F1+2 (ELISA), FVIIa-AT (ELISA) and thrombin generation (TG, CAT assay) were measured. The study protocol was approved by the local Ethics Committee. Informed written consent was obtained from all study subjects. The outcome measure of the current analysis is the time to the occurrence of first symptomatic and/or incidental VTE, objectively confirmed. Results: A cohort of 922 patients [median age: 66 (30-92) years] with metastatic NSCLC (n=416), CRC (n=262), GC (n=105) and BC (n=139) was available for analysis. After a median follow-up of 327 days (range 44-1,548), VTE occurred in 122 (76 M/46 F) patients [median age 64 y (range 40-85)] providing a cumulative incidence of 19.7% (CI 95%: 16-23). According to tumor site, VTE frequency was: NSCLC (n= 64, 15.3%) > CRC (n= 38, 14.5%) > GC (n= 12, 11.4%) > BC (n= 8, 5.7%). Biomarkers' analysis of baseline plasma samples from 598 patients showed significantly higher levels of fibrinogen, d-dimer and TG in the cancer cohort compared to healthy control subjects (p<0.01). NSCLC patients had significantly (p<0.001) higher levels of d-dimer compared to CRC and BC patients, and of fibrinogen (p<0.001) compared to CRC, BC and GC patients. Cumulative incidence of VTE at 6 months was 10% (CI 95% 8-12). In particular, patients who had VTE in 6 months presented with significantly higher pre-chemotherapy levels of D-Dimer than VTE-free subjects (p<0.05). Cox-multivariate analysis identified as independent risk factors for VTE, high d-dimer (HR: 2.1, CI 95% 1.2 - 3.7; p=0.008), high peak of TG (HR: 1.8, CI 95% 0.99 - 3.2; p=0.052), and site of primary tumor (non-BC vs BC) (HR: 3.3, CI 95% 1.01 - 10.5; p=0.048). A score for VTE prediction was created with these variables and three risk categories (low, intermediate, and high) were generated. The cumulative incidence of VTE at 6 months in each risk category was 3.9%, 9.8%, and 19%, respectively (low vs high HR: 2.36 p=0.005; intermediate vs high HR 2.16 p=0.006). Differently, the application of the Khorana score failed to identify high risk patients. Conclusions: Our prospective study in a large cohort of metastatic cancer patients shows the high burden of VTE during the first 6 months of chemotherapy. Furthermore, laboratory data from this analysis enable us to create a risk scoring system based on d-dimer and TG together with tumor site, that significantly identifies patients at the highest VTE risk. Further investigation are worth to externally validate this score for clinical use. Project funded by AIRC "5xMILLE multiunit extension program" n. 12237 grant from the "Italian Association for Cancer Research (AIRC)". Disclosures Santoro: Eisai: Consultancy, Speakers Bureau; Novartis: Speakers Bureau; MSD: Speakers Bureau; Servier: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; BMS: Consultancy; Abb-Vie: Speakers Bureau; Roche: Speakers Bureau; Bayer: Consultancy, Speakers Bureau; AstraZeneca: Speakers Bureau; BMS: Speakers Bureau; Amgen: Speakers Bureau; Celgene: Speakers Bureau; Lilly: Speakers Bureau; Arqule: Consultancy, Speakers Bureau; Gilead: Consultancy, Speakers Bureau; Sandoz: Speakers Bureau; Takeda: Speakers Bureau.

In cancer patients, hypercoagulability is a common finding. It has been associated with an increased risk of venous thromboembolism, but also to tumor proliferation and progression. In this prospective study of a large cohort of breast cancer patients, we aimed to evaluate whether pre-chemotherapy abnormalities in hemostatic biomarkers levels: (i) are associated with breast cancer-specific clinico-pathological features; and (ii) can predict for disease recurrence. D-dimer, fibrinogen, prothrombin fragment 1+2, and FVIIa/antithrombin levels were measured in 701 early-stage resected breast cancer patients candidate to adjuvant chemotherapy and prospectively enrolled in the HYPERCAN study. Significant prognostic parameters for disease recurrence were identified by Cox regression multivariate analysis and used for generating a risk assessment model. Pre-chemotherapy D-dimer, fibrinogen, and pro-thrombin fragment 1+2 levels were significantly associated with tumor size and lymph node metastasis. After 3.4 years of follow up, 71 patients experienced a recurrence. Cox multivariate analysis identified prothrombin fragment 1+2, tumor size, and Luminal B HER2-negative or triple negative molecular subtypes as independent risk factors for disease recurrence. Based on these variables, we generated a risk assessment model that significantly differentiated patients at low- and high-risk of recurrence (cumulative incidence: 6.2 vs 20.7%; Hazard Ratio=3.5; P<0.001). Our prospective clinical and laboratory data from the HYPERCAN study were crucial for generating a scoring model for assessing risk of disease recurrence in resected breast cancer patients, candidate to systemic chemotherapy. This finding stimulates future investigations addressing the role of plasma prothrombin fragment 1+2 in the management of breast cancer patients to provide the rationale for new therapeutic strategies. (The HYPERCAN study is registered at clinicaltrials.gov identifier 02622815).

Introduction: Tumors activate the host hemostatic system, which in turn supports tumor growth and dissemination. In this setting, tumor cell/endothelial cell interactions play a relevant role, particularly by regulating endothelial cell (EC) procoagulant (tissue factor, TF) and anticoagulant (tissue factor pathway inhibitor, TFPI) features.

Adhesion of acute promyelocytic leukemia (APL) cells to endothelial cells (EC) is among the mechanisms of the APL-associated coagulopathy, responsible for early hemorrhagic deaths in affected patients. We compared the effects of dalteparin and enoxaparin, two low-molecular-weight heparins (LMWH), and unfractionated heparin (UFH), on APL NB4 adhesion to micro- (HMEC-1) and macro-vascular EC (HUVEC), in resting and interleukin-1β (IL-1β)-stimulated conditions. The heparin effect on EC adhesion molecule (ICAM-1, VCAM-1, E-selectin) expression was also assessed. In HMEC-1, dalteparin inhibited IL1β-induced NB4 adhesion by 80%, enoxaparin by 52%, and UFH by 44%. Similar results were obtained in HUVEC. This was associated with a significant decrease of VCAM-1 and ICAM-1 expression. In conclusion, we show that LMWH significantly counteract APL cell adhesion to the vessel wall, by modulating EC adhesion molecule expression. This property of heparins may represent one approach for hampering excess clotting activation and microthrombi deposition in APL.

The close relationship between cancer and thrombosis is known since more than a century. Venous thromboembolism (VTE) may be the first manifestation of an occult malignancy in an otherwise healthy individual. Cancer patients commonly present with abnormalities of laboratory coagulation tests, indicating an ongoing subclinical hypercoagulable condition. The results of laboratory tests demonstrate that a process of fibrin formation and removal parallels the development of malignancy, which is of particular interest since fibrin and other clotting products are important for both thrombogenesis and tumor progression. Besides general clinical risk factors (i.e. age, previous VTE, immobility, etc.), other factors typical of cancer can increase the thrombotic risk in these patients, including the type of cancer, advanced disease stage, and cancer therapies. In addition, biological factors, including tumor cell-specific prothrombotic properties and the host cell inflammatory response to the tumor, play a central role in the pathogenesis of cancer-associated thrombosis. Cancer cells produce and release procoagulant and fibrinolytic proteins, as well as inflammatory cytokines. In addition, they are capable of directly adhering to host cells (i.e. endothelial cells, monocytes, platelets, and neutrophils), thereby stimulating additional prothrombotic properties of the host effector cells. Tumor-shed procoagulant microparticles also contribute to the patient hypercoagulable state. Finally, the changes of stromal cells of the tumor 'niche' induced by tissue factor (TF) highlight new interactions between hemostasis and cancer. Of interest, most of these mechanisms, besides activating the hemostatic system, also promote tumor growth and metastasis, and are regulated by oncogenic events. Indeed, molecular studies demonstrate that oncogenes responsible for the cellular neoplastic transformation drive the programs of hemostatic protein expression and microparticle liberation by cancer tissues. Human and animal experimental models demonstrate that activation of cancer-associated prothrombotic mechanisms parallels the development of overt thrombotic syndromes in vivo.

INTRODUCTION and AIM: The HYPERCAN study is an ongoing prospective Italian multicenter trial, designed to test whether the persistence of a laboratory hypercoagulation abnormalities may predict early cancer diagnosis in healthy subjects (Project A), or prognosis and response to therapy in patients with cancer (Project B). The aim of this abstract is to present a preliminary analysis of data collected for project A.

INTRODUCTION:Essential Thrombocythemia (ET) and Polycythemia Vera (PV) are two MPNs characterized by a "clonal" overproduction of one or more blood cell lines, hypercoagulability, and an increased incidence of thrombosis. ROTEM is a point of care global coagulation assay performed in whole blood, able to evaluate platelets and fibrinogen contributions to the clotting process. Until now few studies evaluated the thromboelastometry profile of MPN patients.AIM:This study assess the feasibility of using ROTEM to characterize the prothrombotic state of MPN patients and to evaluate whether the thromboelastometry profile varies according to mutational status and/or treatment, and is influenced by hemocromocytometric parameters.MATERIALS AND METHODS:Venous blood samples were collected from 39 ET and 23PV patients upon informed consent. Analysis was performed using INTEM and EXTEM reagents, to evaluate the intrinsic and extrinsic pathway, respectively. Maximum clot firmness (MCF, [mm]), which reflects the maximum tensile strength of the thrombus, clotting formation time (CFT [sec]), namely the time that clot takes to increase from 2 to 20mm above baseline, and clotting time (CT [sec]), the time to clot initiation, were recorded. Nineteen healthy subjects acted as a control group.RESULTS:ROTEM analysis showed a hypercoagulable profile in MPN patients, who had shorter CFT and higher MCF compared to controls, both with EXTEM and INTEM reagents; no differences were observed in CT parameters. Platelet count was significantly higher in patients compared to controls (p<0.01). In patients, a strong statistically significant (p<0.01) correlation was found between platelet count, and MCF [r=0.650 (ET), r=0.601 (PV)] or CFT [r=-0.641 (ET), r=-0.558 (PV)]. Multivariate analysis, according to blood cell counts, showed that only platelet count was independently associated to ROTEM results. To correct for platelet differences, a ratio between MCF and the respective platelet value (rMCF) was created. Interestingly, rMCF was significantly lower in patients compared to controls (p<0.01), suggesting a weaker clot formation potential of patients' samples. Furthermore, rMCF was lower in ET compared to PV (p<0.05), and in calreticulin-positive subjects (p<0.05), while was higher in patients under cytoreductive therapy (Hydroxyurea) (p=ns).CONCLUSIONS:This study confirms, by the ROTEM evaluation, the occurrence of a hypercoagulable state in ET and PV patients. In addition, the ROTEM parameters are significantly influenced by the platelet count. Finally, MCF values corrected for platelet count reveal a lower platelet reactivity in MPN patients, confirming the hypothesis that platelet function is exhausted upon clotting activation.ACKNOWLEDGEMENT:Project funded by "AIRC-IG2013" grant Nr. 14505 from the "Italian Association for Cancer Research" (A.I.R.C.).