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Abstract To provide direct comparison between apixaban and rivaroxaban in patients with acute cancer‐associated venous thromboembolism (Ca‐VTE), consecutive patients treated with apixaban, rivaroxaban, or enoxaparin at Mayo Thrombophilia Clinic (March 1, 2013 to January 31, 2018)) were followed prospectively. The primary effectiveness outcome was venous thromboembolism (VTE) recurrence, and the secondary was mortality. The primary safety outcome was major bleeding, the secondary clinically relevant safety outcome was non‐major bleeding (CRNMB), and the third a composite of major and CRNMB. There were 750 patients treated for acute Ca‐VTE with apixaban (n = 224), rivaroxaban (n = 163), and enoxaparin (n = 363) within 14 days of diagnosis and for at least 3 months, or until study event. Recurrent VTE was diagnosed in 11 receiving apixaban, 7 receiving rivaroxaban (apixaban vs rivaroxaban hazard ratio (HR) 1.31, 95% confidence interval (95% CI) 0.51‐3.36) and 17 in the enoxaparin receiving group (apixaban vs enoxaparin HR 1.14, 95% CI: 0.54, 2.42 and rivaroxaban vs enoxaparin HR 0.85, 95% Cl: 0.36, 2.06). There were 82 deaths in apixaban, 74 rivaroxaban (apixaban vs rivaroxaban HR 1.67, 95% Cl: 1.20, 2.33) and 171 in enoxaparin group (rivaroxaban vs enoxaparin HR 0.73, 95% Cl: 0.56, 0.96). Major bleeding occurred in 11 apixaban, 12 rivaroxaban (apixaban vs rivaroxaban HR 0.73, 95% Cl: 0.32, 1.66) and 21 enoxaparin group (apixaban vs enoxaparin HR 0.89, 95% Cl: 0.43, 1.84 and rivaroxaban vs enoxaparin HR 1.23, 95% Cl: 0.61, 2.50). The CRNMB rate was higher in rivaroxaban compared to apixaban ( P = .03) and LMWH ( P = .01) groups. Recurrence of VTE and major bleeding were similar in apixaban, rivaroxaban, and enoxaparin groups. Rivaroxaban was associated with higher CRNMB but lower mortality compared to apixaban and enoxaparin.

e23156 Background: A direct meta-analysis was performed to explore the efficacy and safety of direct oral factor Xa inhibitors with dalteparin in patients with cancer associated acute venous thromboembolism (VTE). Also, the comparative efficacy and safety of apixaban, rivaroxaban, and edoxaban was assessed with a network meta-analysis. Methods: MEDLINE, CENTRAL, and EMBASE were searched for trials comparing direct oral anticoagulants (DOACs) to dalteparin for the management of cancer associated acute VTE. A network meta-analysis using both frequentist and Bayesian methods was performed to analyze VTE recurrence, major and clinically relevant non-major bleeding (CRNMB). Results: Three randomized control trials, at low risk of bias, enrolled 1,739 patients with cancer associated VTE. Direct comparison showed a lower rate of VTE recurrence in DOAC compared to dalteparin groups (odds Ratio [OR]:0.48, 95% Confidence interval [CI]:0.24-0.96; I2:46%). Indirect comparison suggested that apixaban had greater reduction in VTE recurrence compared to dalteparin (OR: 0.10; 95% CI: 0.01–0.82), but not rivaroxaban or edoxaban. Apixaban also had the highest probability of being ranked most effective. By direct comparisons, there was an increased likelihood of major bleeding in the DOAC group compared to dalteparin (OR: 1.70; 95% CI: 1.04–2.78). CRNMB did not differ. Indirect estimates were imprecise. Subgroup analyses in gastrointestinal cancers suggested that dalteparin may have the lowest risk of bleeding whereas estimates in urothelial cancer were imprecise. Conclusions: DOACs appear to lower the risk of VTE recurrence compared to daltaparin while increasing major bleeding. Apixaban may be associated with the lowest risk of VTE recurrence compared to the other DOACs.

Background: The AMPLIFY randomized clinical trial showed that apixaban was associated with significantly lower major bleeding (MB) compared to warfarin for patients with venous thromboembolism (VTE). The main objective of this study was to compare the risk of major bleeding (MB), clinically relevant non-major bleeding (CRNM), and recurrent VTE among VTE patients treated with apixaban vs warfarin in the US Medicare population. Methods: Patients (aged ≥65 years) prescribed apixaban or warfarin within 30 days following a VTE event diagnosed in hospital or ambulatory setting were identified from 01SEPT2014-31DEC2016 using 100% CMS Medicare data. The first apixaban or warfarin prescription claim outside of the hospital was defined as the index date. Patients were required to have had continuous health plan enrollment for 6 months and no parenteral or oral anticoagulant use before the index VTE event. Outcomes were assessed from index date to the earliest of discontinuation, switch, health plan disenrollment, death, 6 months post-index date, or 31DEC2016. One-to-one propensity score matching (PSM) was used to balance patient characteristics. Cox proportional hazard models were used to estimate the risk of MB, CRNM bleeding, and recurrent VTE. Results: Among 37,799 patients meeting inclusion criteria, 25,284 patients initiated warfarin (66.9%) and 12,515 patients initiated apixaban (33.1%). Post-PSM, 11,363 matched pairs of apixaban-warfarin patients were identified, with a mean follow-up period of 4.0 and 4.4 months. Mean age was 78 years; nearly 37% of patients were male with a mean Charlson Comorbidity Index score of 2.9 in both groups. Apixaban was associated with a lower risk of MB (HR: 0.76; 95% CI: 0.64-0.91) and CRNM bleeding (HR: 0.77; 95% CI: 0.70-0.84) compared to warfarin. The risk of recurrent VTE was similar among apixaban and warfarin patients (HR: 1.04; 95% CI: 0.75-1.43; Figure). Conclusions: Among US Medicare patients with VTE, apixaban was associated with a lower risk of MB and CRNM bleeding and similar risk of recurrent VTE compared to warfarin. These results may be supportive in evaluating the risk-benefit ratio of apixaban for treatment of elderly VTE patients.

SummaryReversibility in vivo of acute platelet thrombosis in response to specific anticoagulants is analyzed with thrombi that develop in segments (1 cm) of porcine carotid arteries externally crushed with a hemostat. Most thrombi fill the lumens of the injured segments (ca. 1 cm × 3 mm, 1 × w) within 30 min and comprise masses of platelets interpenetrated with neutrophil-lined seepage channels of blood. Continuous quantitative assay of thrombus mass is provided by a gamma detector placed over the injured segments to collect counts from 111In-labeled platelets. Thrombi established 30 min after injury, otherwise stable for 6 h, clear during 30-60 min of continuous infusion of either hirudin, tick anticoagulant or activated porcine protein C, or intermittent activation of endogenous protein C with a latent thrombin reagent. Anticoagulant dose-dependence of thrombus clearance is established for hirudin between 0.01 and 1.0 mg/kg/min. Thrombi become progressively refractory to hirudin between 0.5 and 6 h after injury. Neither heparin nor low-molecular-weight heparin in full (clinical) anticoagulant doses yield significant dethrombosis. It is concluded that, within time limits, controlled thrombin generation in platelet thrombi maintains platelet cohesion without catalyzing irreversible platelet aggregation or clotting of fibrinogen.

AbstractBackgroundLow molecular weight heparin (LMWH) is the guideline‐endorsed treatment for cancer‐associated venous thromboembolism (cVTE). Study objectives were to compare the efficacy and safety of rivaroxaban and enoxaparin in cVTE.MethodsUsing a cohort study design, consecutive patients with cVTE (3/1/2013‐7/31/2016), enrolled in the Mayo Thrombophilia Clinic Direct Oral Anticoagulants Registry, were compared to contemporary cancer patients receiving enoxaparin. The cumulative incidence of venous thromboembolism (VTE) recurrence, major and clinically relevant non‐major bleeding, and survival were assessed at 3 and 12 months.ResultsNinety‐eight patients received rivaroxaban (51% female, mean age 63 ± 12 years) and 168 enoxaparin (34.5% female, mean age 62 ± 15 years). The most common cancers included gastrointestinal/pancreatic, genitourinary and hematologic cancers. More than half of patients had pulmonary emboli at presentation. More than half had metastases, and two‐thirds were receiving chemotherapy. At 3 months, there were no differences in VTE recurrence (rivaroxaban 1.0% vs enoxaparin 4.2%; P = .15), major bleeding (rivaroxaban 5.1% vs enoxaparin 3.6%; P = .55), or all‐cause mortality (rivaroxaban 4.1% vs enoxaparin 8.9%; P = .14). At 12 months, these outcomes did not differ by treatment strategy.ConclusionThe results of this “real‐world” experience with cVTE suggest that rivaroxaban may offer a safe and effective alternative to LMWH.